Table 2. Studies on the individual learning abilities of tool-using animals.
| Species | Reference | Testing methodology | Findings | Authors’ interpretation |
|---|---|---|---|---|
| Great Apes | ||||
| Bonobos (Pan paniscus) | Boose, White & Meinelt (2013) | Experimental study in captivity | The first individual to both attempt and successfully fish was a naïve juvenile female who investigated the mound, manufactured a tool, attempted, and successfully fished on the first baited trial presented to the bonobos. All the other members of the group eventually showed the same behaviour | ‘Following Lonsdorf et al. (2009), “investigation” of the mound was defined as using visual and olfactory senses to examine the contents of the bait holes in order to identify when subjects were first clearly aware that the termite mound contained bait. This definition appeared appropriate for most individuals, except for one. Maiko, a low-ranking male, did not investigate the mound under this definition, but was in the vicinity of fishing individuals on several occasions prior to his first attempt. In this single case, it appears that Maiko used information from observing the behaviours of other group members to identify that the mound contained bait’ (p.923) |
| Bonobos (Pan paniscus) | Roffman et al. (2015) | Experimental study in captivity | All the bonobos in the group used modified branches and unmodified antlers or stones to dig under rocks and in the ground or to break bones to retrieve the food | ‘Interestingly, the digging techniques used by PB and her son NY, who shared much time together, were very similar, possibly indicating social learning by NY. Likewise, some individuals in the WZ group (LB, BR, EJ) used tools occasionally, whereas others (MA, LA, LO, BZ, BO) did so rarely or not at all’ (p.88) |
| Chimpanzees (Pan troglodytes schweinfurthii) | Hobaiter et al. (2014) | Observational study in the wild | Two chimpanzees independently demonstrated the first of the two novel behaviours (moss-sponging) and five individuals demonstrated the second novel behaviour (moss-sponge re-use). | ‘Here, we tested both a static and a dynamic network model and found strong evidence that diffusion patterns of moss-sponging, but not leaf-sponge re-use, were significantly better explained by social than individual learning. The most conservative estimate of social transmission accounted for 85% of observed events, with an estimated 15-fold increase in learning rate for each time a novice observed an informed individual moss-sponging. We conclude that group-specific behavioural variants in wild chimpanzees can be socially learned, adding to the evidence that this prerequisite for culture originated in a common ancestor of great apes and humans, long before the advent of modern humans’ (p.1) |
| Chimpanzees (Pan troglodytes schweinfurthii) | Morgan & Abwe (2006) | Observational study in the wild | First observation (albeit indirect) of population-wide nut cracking in Cameroon | ‘This observation challenges the existing model of the cultural diffusion of nut-cracking behaviour by implying that it has been invented on multiple occasions’ (p.1) |
| Chimpanzees (Pan troglodytes schweinfurthii) | Yamamoto et al. (2008) | Observational study in the wild | Spontaneous ant-fishing by one individual over an extended time period (two observations over 2 years). So far this behaviour has only been observed in this one individual. | ‘The motivation to use tools may not only encourage young chimpanzees to socially learn transmitted tool use behaviours but may also lead them to innovate new tool use behaviours through individual exploration and trial and error leaning’ (p.701) |
| Chimpanzees (Pan troglodytes) | Alp (1997) | Observational study in the wild | Eight chimpanzees were observed using sticks as foot and body protection against thorns while foraging | ‘This form of tool-using is culturally unique to the Tenkere chimpanzees, as at other sites where these apes have been observed eating parts of kapok trees, there are no published records of this tool technology. In three of the stepping-stick tool use incidents, the chimpanzee used the tool(s), held between their greater and lesser toes, in locomotion. This form of tool use is the first recorded case of habitually used tools that can be justifiably categorised as being “worn” by any known wild population’ (p.1) |
| Chimpanzees (Pan troglodytes) | Bandini & Tennie (2017) | Experimental study in captivity | Two chimpanzees (one in each group) spontaneously reinnovated the same technique for scooping | ‘Our results demonstrate that the wild form of scooping behaviour re-appeared independently in two naive chimpanzees (it was reinnovated twice). Thus, unlike human cumulative cultural behaviour, the observed patterns of scooping behaviour in the wild can be explained via Socially Mediated Serial Reinnovations (SMSR)’ (p.13) |
| Chimpanzees (Pan troglodytes) | Bandini & Tennie (2019) | Experimental study in captivity | Three individuals spontaneously used tools to show the same pounding behavioural form | ‘At least three individuals spontaneously reinnovated the stick pounding behaviour examined in this study (one individual in group one, two and four). In all three groups, the naïve chimpanzees used sticks and a pounding action to retrieve the bait at the bottom of the testing apparatus. These findings surpass the double-case ZLS standard and therefore suggest that stick pounding is a behaviour that can reinnovated via individual learning’ (p.16) |
| Chimpanzees (Pan troglodytes) | Bernstein-Kurtycz et al. (2020) | Experimental study in captivity | Six chimpanzees used two different tools (one ridgid and one flexible) to retrieve a reward from an artifical termite mound | ‘Overall, chimpanzees did use both tool types in order, thus demonstrating that this tool-set form is not a CDT. Yet, few attempts were successful, and the majority were not made using a tool set. This suggests that the behaviour did not stabilise, which may have been due to unintentional difficulty created by the opacity of the task. Overall, our study showed that the form of tool sets can be within the ZLS of chimpanzees, but future studies need to determine what stabilises the behavioural patterns in the wild’ (p.1) |
| Chimpanzees (Pan troglodytes) | Birch (1945) | Experimental study in captivity | Two individuals used sticks to rake in the food in the first testing condition. Over the course of 3 days of exposure to the sticks, every one of the subjects succeeded in solving the problem within a period of 20 s | ‘That insightful problem solution represents the integration into new patterns of activity of previously existent part-processes developed in the course of the animals’ earlier activities’ (p.382) |
| Chimpanzees (Pan troglodytes) | Davis et al. (2016) | Experimental study in captivity | Two naïve chimpanzees in the control group spontaneously discovered the more efficient method for removing the token from the puzzle box | ‘When their foraging method became substantially less efficient, nine chimpanzees with socially-acquired information (four of whom witnessed additional human demonstrations) relinquished their old behaviour in favour of the more efficient one. Only a single chimpanzee in control groups, who had not witnessed a knowledgeable model, discovered this. Individuals who switched were later able to combine components of their two learned techniques to produce a more efficient solution than their extensively used, original foraging method. These results suggest that, although chimpanzees show a considerable degree of conservatism, they also have an ability to combine independent behaviours to produce efficient compound action sequences; one of the foundational abilities (or candidate mechanisms) for human cumulative culture’ (p.2) |
| Chimpanzees (Pan troglodytes) | Devos, Gatti & Levrero (2002) | Observational study in the wild | First observation of spontaneous algae scooping with a tool by one chimpanzee | No interpretation offered by the authors |
| Chimpanzees (Pan troglodytes) | Harrison & Whiten (2018) | Experimental study in captivity | The chimpanzees spontaneously used tools to access the juice in the first condition, however did not switch to more efficient techniques when access to the juice was restricted, even when sticks were placed inside the apparatus (providing a ‘scaffolded condition’) the subjects still did not adopt the more efficient technique | ‘The limited exposure to scaffolding provided to four chimpanzees in the third and final phase of this study did not lead to the acquisition of novel techniques by any individual’ (p.18) |
| Chimpanzees (Pan troglodytes) | Hirata, Morimura & Houki (2009) | Experimental study in captivity | During one of the pre-training tests, and after some exposure to the materials, the demonstrator (before being trained in the behaviour), spontaneously cracked open the nuts provided with the stones. In the pre-tests, one individual from the rest of the group also showed pre-cursors to nut-cracking by placing a nut on an anvil and hitting it with one of the stones. The attempts were never successful, however. The whole group eventually acquired the full behaviour, but this was after demonstrations had been carried out. | ‘Another implication of this study is the effect of observing a model. It is difficult to prove the effect of observing a model in our study because we lack control data on how the chimpanzees would have behaved if they had not observed a model. However, we can make some inferences about social influences on learning. First, the chimpanzees in our study performed less-advanced manipulations in the pre-test situation before observing a model, and they showed continuous progress in the presence of a model. However, it is also true that they did not show evidence of immediate true imitation (Whiten & Ham, 1992). Their behaviour did not clearly improve immediately after observing successful nut cracking by a peer’ (p.21) |
| Chimpanzees (Pan troglodytes) | Hopper et al. (2007) | Experimental study in captivity | One individual in the ‘lift’ seeded group spontaneously reinnovated the ‘poke’ methodology. | ‘Poke was also not discovered by control animals tested individually. However, Poke emerged spontaneously in the Lift group and became dominant in both groups, regardless of the founder’s Lift or Poke technique. Accordingly, this study demonstrated a statistically significant, differential spread of alternative techniques through social learning, yet no clear separation of traditions, unlike an earlier study with a different population of chimpanzees. This difference may be attributable to prior experience with relevant tools. In further experiments we investigated the basis of the social learning evident in acquisition of the Lift technique, using ‘ghost’ conditions in which the task was operated automatically rather than by a chimpanzee. Differential movement of the feeding device either by itself or with the tool coupled to it was not sufficient for learning to occur. It appears necessary for a chimpanzee to observe another chimpanzee performing the Lift technique for transmission to ensue’ (p.1021) |
| Chimpanzees (Pan troglodytes) | Kitahara-Frisch & Norikoshi (1982) | Experimental study in captivity | Two chimpanzees spontaneously used the leafy branches to retrieve the juice from the apparatus | ‘The sponging behaviour as practised by zoo chimpanzees indicates that the example of the mother is by no means necessary for the habit to appear in young animals. This observation raises the question whether the acquisition of so-called proto-cultural habits does not rely as much, at least, on independent reinvention as on transmission through imitation learning. It is concluded that the sponge-making behaviour observed in Gombe can most parsimoniously be interpreted as an incidental corollary of a highly variable and potentially meaningful expression of the chimpanzee’s behavioural resourcefulness’ (p.41) |
| Chimpanzees (Pan troglodytes) | Köhler (1925) | Experimental study in captivity | Most of the tested chimpanzees spontaneously used the tools to rake in or reach the food | ‘It is most difficult for chimpanzees to imitate anything, unless they themselves understand it (p.157)…when it (imitation) does occur, the situation, as well as its solution, must lie just about within the bounds set for spontaneous solution’ (p.222) |
| Chimpanzees (Pan troglodytes) | Kummer & Goodall (1985) | Observational study in the wild | Report of chimpanzees at Gombe spontaneously using sticks to lever open boxes that contained bananas | ‘One new behaviour that did spread through the community at Gombe was the use of sticks as levers to try to open banana boxes. Four and a half months after these boxes had been installed three adolescents began, independently, to use sticks to try to prize open the steel lids. Because a box was sometimes opened when a chimpanzee was working at it, the tool use was occasionally rewarded and, over the next year, the habit spread until almost all members of the community, including adult males, were seen using sticks in this way. That many individuals learnt as a result of watching their companions is suggested by the fact that one female was observed to behave thus on her very first visit to camp: before this she had had ample opportunity to watch what was going on from the surrounding vegetation (Goodall, 1986)’ (p.212) |
| Chimpanzees (Pan troglodytes) | Manrique & Call (2011) | Experimental study in captivity | In experiment 1, four orangutans and one chimpanzee invented the use of a piece of electric cable to get the juice. Experiment 2 investigated whether subjects could transform a non-functional hose into a functional one by removing blockages that impeded the free flow of juice. Orangutans outperformed chimpanzees and bonobos by differentially removing those blockages that prevented the flow of juice, often doing so before attempting to extract the juice | ‘In conclusion, orangutans proved to be more innovative than bonobos and most chimpanzees by inventing the use of tools as straws and modifying non-functional tools when needed. Moreover, some orangutans introduced the required modification prior to using the tools and were able to select novel suitable tools without having to try them first’ (p.225) |
| Chimpanzees (Pan troglodytes) | Menzel, Davenport & Rogers (1970) | Experimental study in captivity | All the subjects spontaneously used sticks to rake in the bananas | ‘The present data clearly show that early experience of a very general sort, before the age at which wild chimpanzees generally ordinarily become proficient at instrumental activities with objects, is required before animals can fully profit from later opportunities’ (p.281) |
| Chimpanzees (Pan troglodytes) | Morimura (2003) | Experimental study in captivity | All the subjects spontaneously used sticks to retrieve the juice | ‘This finding demonstrated that when chimpanzees have the option to access juice through a variety of methods, they employ all available choices. It also supported the hypothesis that the behaviour of captive chimpanzees may come to resemble that of their wild counterparts as a function of behavioural freedom’ (p.241) |
| Chimpanzees (Pan troglodytes) | Motes-Rodrigo et al. (2019) | Experimental study in captivity | All of the chimpanzees spontaneously used sticks to dig for the buried food | No interpretation offered by the authors |
| Chimpanzees (Pan troglodytes) | Nash (1982) | Experimental study in captivity | All the subjects used sticks to dip into the termite mound to retrieve the baited food | ‘The artificial mound proved to be a viable simulation of the naturally occurring mounds, with most of the chimpanzees exploiting the food in the mound by using tools over the period of study. Interesting individual differences emerged in the way that the chimpanzees selected and used tools, some preferring to move some distance from the mound to collect “off-the-peg” tools. others preferring to sit and fashion a tool from material available nearer the mound. Also, some chimpanzees used both ends of a tool, while others used only one end’ (p.211) |
| Chimpanzees (Pan troglodytes) | Price et al. (2009) | Experimental study in captivity | Two subjects were observed as being successful combiners and two twist-extenders in control condition | ‘Social learning, therefore, had a powerful effect in instilling a marked persistence in the use of a complex technique at the cost of efficiency, inhibiting insightful tool use’ (p.3377) |
| Chimpanzees (Pan troglodytes) | Tomasello et al. (1987) | Experimental study in captivity | One individual in the control group used the tool as a rake | ‘None of the subjects demonstrated an ability to imitatively copy the demonstrator’s precise behavioural strategies. More than simple stimulus enhancement was involved, however, since both groups manipulated the T-bar, but only experimental subjects used it in its function as a tool. Our findings complement naturalistic observations in suggesting that chimpanzee tool-use is in some sense ‘culturally transmitted’—though perhaps not in the same sense as social-conventional behaviours for which precise copying of conspecifics is crucial’ (p.175) |
| Chimpanzees (Pan troglodytes) | Vale et al. (2017) | Experimental study in captivity | The chimpanzees in the asocial control group, in which the behaviours were not seeded eventually individually acquired all of the methods to retrieve the bait, other than the ‘unscrew’ and ‘suck’ behaviours. | ‘Five chimpanzees tested individually with no social information, but with experience of simple unmodified tool use, invented part, but not all, of the behavioural sequence. Our findings indicate that (i) social learning facilitated the propagation of the model-demonstrated tool modification technique, (ii) experience with simple tool behaviours may facilitate individual discovery of more complex tool manipulations, and (iii) a subset of individuals were capable of learning relatively complex behaviours either by learning asocially and socially or by repeated invention over time. That chimpanzees learn increasingly complex behaviours through social and asocial learning suggests that humans’ extraordinary ability to do so was built on such prior foundations (p.635)… ‘Thus, our captive populations, much like what has been documented in other captive populations (Hopper et al., 2014), were capable of re-inventing means in which their wild counterparts make and use tools.’ As some individuals in one of the non-seeded groups eventually discovered the full behaviour, we cannot be sure that discovering it is outside the innovation capabilities of at least some chimpanzees (referred to by Tennie, Call & Tomasello (2009) as their ‘zone of latent solutions’)’ (p.642) |
| Chimpanzees (Pan troglodytes) | Watson et al. (2017) | Experimental study in captivity | One chimpanzee innovated a new solution: to slide the door up far enough to reach reward but not to lock mechanism, allowing her to then slide it down and retrieve a second reward | ‘While this study has shown that chimpanzees are motivated to learn novel methods of accessing a resource from subordinate individuals, it is possible this is not true of forms of imitative behaviour that are thought to be normatively motivated and therefore, perhaps particularly directed toward important social partners’ (p.23) |
| Chimpanzees (Pan troglodytes) | Whiten, Horner & De Waal (2005) | Experimental study in captivity | At least four chimpanzees in the seeded groups developed the alternative method to access the pan-pipes apparatus | ‘Additionally, the ‘two alternatives’ methodology shows that learning involves not merely the facilitation of an existing competence, but a capacity to acquire particular local variants of the technique, precisely as required if the behavioural variants identified in wild populations are indeed socially transmitted’ (p.738) |
| Chimpanzees (Pan troglodytes), bonobos (Pan paniscus) and orangutans (Pongo pygmaeus abelii) | Visalberghi, Fragaszy & Savage-Rumbaugh (1995) | Experimental study in captivity | All the tested species spontaneously solved both the simple and complex forms of the tasks, and inserted sticks into the tubes to retrieve the rewards | ‘In conclusion, apes and capuchins can achieve success in a tool-using task and still have an apparently limited understanding of the causal relations involved (Visalberghi & Limongelli, 1994). This is also apparently true for human children (E. Visalberghi and A. Troise, 1994, unpublished data). We believe that successful use of an object as a tool to probe, rake, pound, or contain (the kinds of experimental tool-using tasks usually presented to non human primates) can be achieved through frequent spontaneous combinations of actions and objects, particularly objects with other objects or surfaces (Fragaszy & Adams-Curtis, 1991; Schiller, 1952). It appears that the experience of using tools does not, by itself, lead to or require the emergence of additional conceptual complexity’ (p.59) |
| Chimpanzees (Pan troglodytes), gorillas (Gorilla gorilla gorilla), and orangutans (Pongo pygmaeus abelii) | Hanus et al. (2011) | Experimental study in captivity | Five individuals spontaneously developed the same solution of spitting into the tube to make the peanut float to the surface | ‘According to the latency data (e.g. appearance of the first spit) the extra information of water inside the tube (wet condition) did not seem to stimulate chimpanzees’ inventiveness. Furthermore, control tests showed that successful chimpanzees preferentially added water to the tube when the peanut was inside the tube, not simply when the peanut was present yet out of reach. Chimpanzees seemed to add water exclusively to affect the position of the peanut, which confirms the goal-directedness of their behaviour. Results are also consistent with the notion of insightful behaviour’ (p.8) |
| Gorilla (Gorilla gorilla gorilla) | Boysen et al. (1999) | Experimental study in captivity | All the tested gorillas spontaneously used stick tools to fish peanut butter out from the artificial dome | ‘Currently there is no compelling evidence to suggest that great apes are capable of reproducing a model’s novel actions to obtain a goal in problem-solving situations (i.e. imitative learning)’ (p.338) |
| Gorilla (Gorilla gorilla gorilla) | Breuer, Ndoundou-Hockemba & Fishlock (2005) | Observational study in the wild | An adult female gorilla was observed using a branch as a walking stick to test the water deepness and to aid in her attempt to cross a pool of water. In the second case, another adult female was observed using a detached trunk from a small shrub as a stabiliser during food processing. She then used the trunk as a self-made bridge to cross a deep patch of swamp | ‘The observed tool use involved gorillas from two different groups and thus could indicate independent inventions, perhaps reflecting past negative experiences with deep water’ (p.2042) |
| Gorilla (Gorilla gorilla gorilla) | Fontaine, Moisson & Wickings (1995) | Observational study in captivity | Captive gorillas spontaneously used tools to rake in objects outside of their enclosure, as weapons, to sponge liquids and as ladders | ‘The gorillas were not intentionally taught any of the skills described here. Although, in themselves the tasks accomplished with the materials at hand were relatively simple, their diversity is remarkable and indicative of certain innate cognitive skills rather than behaviour learnt by observing human activity’ (p.223) |
| Gorilla (Gorilla gorilla gorilla) | Nakamichi (1999) | Observational study in captivity | Three captive gorillas (one female and two males) threw sticks into the foliage of trees, which the gorillas could not climb due to electric wire, to knock down leaves and seeds | ‘This behaviour might originate from the nest-building behaviour which is commonly performed by gorillas in the wild’ (p.494) |
| Gorilla (Gorilla gorilla gorilla) | Natale, Poti’ & Spinozzi (1988) | Experimental study in captivity | Both the gorilla and the macaque spontaneously used the sticks provided to rake in the out-of-reach food | ‘This difficulty in dealing with certain physical constraints is consistent with the hypothesis of a general lag in the development of physical cognition of non-human primates, which was suggested in previous studies of early sensorimotor development’ (p.415) |
| Gorilla (Gorilla gorilla gorilla) | Pouydebat et al. (2005) | Experimental study in captivity | Every subject was able to make and use tools to extract food spontaneously. They carried branches to the apparatus, then broke them and removed projections such as leaves and bark | ‘Our study attests to the fact that western lowland gorillas are able to manufacture and use food-extracting tools in a chimpanzee-like manner. The gorillas were able to adapt tools to a particular use by selecting branches and adapting their length to the depth of the holes. They may also anticipate the use of the tool, by beginning with the largest stick and progressively shortening it’ (p.182) |
| Gorilla (Gorilla gorilla gorilla) | Wood (1984) | Observational study in captivity | Spontaneous stick tool use by gorillas | No interpretation offered by the authors |
| Gorillas (Gorilla beringei beringei) | Kinani & Zimmerman (2015) | Observational study in the wild | A young gorilla first tried to retrieve ants from an ant hole with her arm, but soon after selected a piece of wood and proceeded to insert the stick into the hole, withdraw the stick, and then lick ants off of the stick | ‘This is the first time tool use has been reported in a wild mountain gorilla despite the intensive monitoring of this subspecies. The described tool use event is characterised as idiosyncratic and can, in part, be explained by Lisanga’s curious nature as she is known to have an investigative personality. Furthermore, Leca, Gunst & Huffman (2010) mentioned that, despite the numerous examples of socially-transmitted tool use innovations in several non-human primate species, it should be noted that only a subset of such innovations become tradition and a large part of whether this happens likely depends on cost-benefit considerations. For wild mountain gorillas, ants are not a significant part of their diet perhaps because they do not offer substantial nutritional value per mass ingested, because other food sources are readily available, and/or because they are difficult to obtain without getting bitten’ (p.355) |
| Gorillas (Gorilla gorilla gorilla) | Neadle, Allritz & Tennie (2017) | Experimental study in captivity | All subjects showed evidence of cleaning the apples in 75% of the trials | ‘Given this occurrence of food cleaning in a culturally unconnected population of gorillas, we conclude that social learning is unlikely to play a central role in the emergence of the food cleaning behavioural form in Western lowland gorillas; instead, placing a greater emphasis on individual learning of food cleaning’s behavioural form’ (p.1) |
| Gorillas (Gorilla gorilla gorilla), chimpanzees (Pan troglodytes) | Lonsdorf et al. (2009) | Experimental study in captivity | All chimpanzees except for the alpha male attempted to fish on the very first trial. Some gorillas were successful on the first day and some individuals never attempted the task even after 60 bait trials | ‘Together, these results suggest that chimpanzees may be better equipped to acquire knowledge that is socially transmitted. Whether individual or social learning is necessary to learn the task, access to the device is critical, and our observations suggest that, in gorillas, subordinate individuals may be socially constrained from accessing the termite mound’ (p.1119) |
| Orangutan (Pongo pygmaeus abelii) | Mendes, Hanus & Call (2007) | Experimental study in captivity | All the orangutans collected water from a drinker and spat it inside the tube to get access to the peanut | ‘The sudden acquisition of the behaviour, the timing of the actions and the differences with the control conditions make this behaviour a likely candidate for insightful problem solving’ (p.453) |
| Orangutan (Pongo pygmaeus abelii) | Bandini et al. (2020a) | Experimental study in captivity | One juvenile orangutan spontaneously started cracking nuts using the tools provided | No interpretation offered by the authors |
| Orangutan (Pongo pygmaeus abelii) | Lehner, Burkart & Van Schaik (2011) | Experimental study in captivity | Naive captive orangutans first spontaneously started using sticks to retrieve liquids from a testing apparatus, and then built upon this behaviour to create more efficient techniques when the simple branch-dipping method was rendered inefficient | ‘Most subjects started with a nonefficient technique (“dip stick”), but then spontaneously came up with innovative and more efficient solutions, and eventually largely switched to these and preferentially used them. Minimally, this indicates that they recognised which of two techniques yields a higher return. At the same time, most individuals kept on using a variety of techniques under the regular condition, predicting they would show high flexibility to abandon preferred techniques and switch to different techniques as the condition was changed’ (p.453) |
| Orangutan (Pongo pygmaeus abelii) | Nakamichi (2004) | Experimental study in captivity | Three adult orangutans spontaneously stripped leaves and twigs from a branch provided and then inserted the tool into a hole to obtain the baited food. When the orangutans were unable to insert a tool into a hole, they modified the tool and/or changed their tool-using technique, such as changing how they grasped the tool | ‘Analysing the spontaneous use of sticks as tools by gorillas in captivity can lead to a better understanding of not only their cognitive ability but also of their social relationships, which may otherwise be concealed’ (p.487) |
| Monkeys | ||||
| Baboons (Papio anubis) | Benhar & Samuel (1978) | Experimental study in captivity | Both of the tested baboons used the metal hooks provided to pull up the bread | ‘The successful use of a tool by two baboons in our colony indicates that “specific training” was not necessary, since these animals had previously used their tails for retrieval. These results support the statement by Hall (1963) that baboons have so far not been seen to demonstrate tool-using in the wild for food seeking behaviour, but they do so readily when given the opportunity in captivity’ (p.388) |
| Baboons (Papio cynocephalus anubis) | Westergaard (1992) | Experimental study in captivity | The baboons used paper, browse, and other materials as tools to extract sweet liquids from the apparatus | ‘Results demonstrate flexible combinatorial manipulation and spontaneous use of tools by infant baboons. These data are consistent with hypotheses that (1) an evolutionary history of omnivorous extractive foraging is associated with the use of tools and (2) free play in an object-enriched captive environment may facilitate combinatorial manipulation in nonhuman primates’ (p.1) |
| Baboons (Papio papio) | Beck (1973) | Experimental study in captivity | A sub adult male spontaneously used a tool to rake in food. Only one other individual demonstrated the same behaviour after a long period in which only the first male was using a tool as a rake | ‘A sub adult male from a captive group of Guinea baboons learned, by trial-and-error, to use a tool to rake in food. He then used the tool 104 times over 26 days, thereby providing the group with most of its food. No other group member used the tool during this period. The tool user was removed, and the remainder of the group was given access to the display. None imitated his tool use. It took longer for another finally to learn to use the tool than it had for the initial solution. However, compared with the period before initial solution, group members manipulated the tool more frequently and touched the food pan with the tool nearly twice as many times after the tool user’s separation. This type of tool use appears to be too complex for baboons to imitate directly. However, as a result of observing successful tool use, they attend more to the problem and manipulate the tool more frequently and more accurately. This increase in frequency and accuracy may, in turn, accelerate acquisition of the response by observers through instrumental trial-and-error learning’ (p.579) |
| Baboons (Papio papio) | Petit et al. (1993) | Observational study in captivity | Baboons were found to spontaneously use stones in a pounding action to enlarge a hole in their outdoor enclosure (the purpose behind this behaviour is unknown) | ‘Given the timing of events, it can be inferred that Voy was the initial discoverer and that the acquisition by the other individuals was facilitated by his behaviour…As in other cases of social influence of learning, stimulus enhancement probably played an important part in the dissemination of the behaviour’ (p. 163) |
| Baboons (Papio papio) | Westergaard & Fragaszy (1987) | Experimental study in captivity | Although the macaques did not use any of the materials provided to retrieve the syrup, they did use the sticks and other materials to make ladders to climb to the top of their enclosure | ‘A variety of goal-directed manipulative activities (use of objects to act as ladders, to apply leverage, and to create perches) occurred spontaneously, with some instances involving joint action or social use. These data are consistent with the hypotheses that macaques possess extensive capacities for object exploration and social facilitation, and that an evolutionary history of omnivorous foraging habits correlates positively with the expression of anomalous sensorimotor skills’ (p.231) |
| Black-capped capuchins (Sapajus apella) | Izawa & Mizuno (1976) | Observational study in the wild | On a border of La Macarena National Park in Colombia, the authors observed the feeding behaviour of a black-capped capuchin, in which the monkey fed on the albumen of the fruit of cumare, a kind of cocoid palm-fruit, using two different methods, according to the degree of ripeness of the fruit | ‘The characteristic behaviour developed by the black-capped capuchin while eating the fruit of cumare could be fixed as one of the higher level adaptive behaviours of the animal to his habitat’ (p.1) |
| Capuchins (Cebus apella) | Antinucci & Visalberghi (1986) | Experimental study in captivity | One capuchin spontaneously started cracking nuts with tools when provided with the materials. Always picked the right tool out of several options (stone, wood plastic) | ‘C’s results in the tool condition show that this monkey is capable of appropriately utilising any detached object offered to it as a hammer tool, even if it has no previous experience with it, and that, furthermore, when given a choice, it is also capable of selecting the most efficient object from those available’ (p.361) |
| Capuchins (Cebus apella) | Visalberghi & Trinca (1989) | Experimental study in captivity | Three out of four capuchins spontaneously used sticks to push food out of a tube. They were also successful in modifying the stick when needed | ‘The first success of the adult male has all the characteristics of an insight solution’ (p.519) |
| Capuchins (Cebus libidinosus) | Waga et al. (2006) | Observational study in the wild | Spontaneous emergence of stone tool-use in a group of wild capuchins. The capuchins were observed using stones to crack open hard-shelled Jatoba fruit (Hymenaea courbaril) | ‘We propose that the probability of the emergence of the use of pounding stones as tools may be dependent on the ecological variables that influence the degree of terrestriality and extractive foraging and the complex interaction of these factors’ (p.337) |
| Capuchins (Cebus nigritus) | Bortolini & Bicca-Marques (2007) | Observational study in captvitiy | An adult female was observed banging a twig with a piece of stone against a larger stone, and then licking/chewing and likely extracting something from it with her mouth. She was then observed probing an unseen structure (probably a hole in the enclosure’s drinking fountain) with the modified twig | ‘Although we do not know what happened immediately prior to this behavioural sequence and could not see whether the female acquired anything as a result of probing, the speed at which this sequence of events occurred is highly suggestive of a causal understanding during object manipulation and seems to qualify as a case of spontaneous tool-making’ (p.75) |
| Capuchins (Sapajus apella) | Visalberghi (1987) | Experimental study in captivity | Two capuchins started cracking nuts with blocks spontaneously | ‘In the present study, two tufted capuchins spontaneously acquired a novel form of tool-use, consisting in cracking nuts with a block, which was not innate or stereotyped’ (p.176) |
| Capuchins (Sapajus apella) | Westergaard & Fragaszy (1985) | Experimental study in captivity | The capuchins spontaneously started using cups as drinking tools and to carry objects around the enclosure. Also used paper-towels as sponges to soak up water | ‘The repeated, spontaneous use of provided objects as tools in this group further illustrates the influence of environmental conditions on the form and frequency of activity in captive primate groups’ (p.326) |
| Capuchins (Sapajus apella) | Westergaard & Fragaszy (1987) | Experimental study in captivity | Several of the subjects spontaneously manufactured and used tools to scoop water from their water bowls. Subsequently other objects that had been provided (such as tupperwares) were used to transport water, food, and other objects across the enclosure | ‘Immature monkeys in this group developed tool-use more gradually than adults. However, subsequent to initial success, immature monkeys quickly became as proficient as adults that used tools’ (p.327) |
| Capuchins (Sapajus apella) | Westergaard & Suomi (1994a) | Experimental study in captivity | Several of the naive capuchins spontaneously hit the hammerstone against the core to make sharp flakes. The flakes were then used to cut open the puzzle box | ‘We suggest that the ability to make and use simple stone tools may have been discovered numerous times and utilised by more than one hominid genus and species’ (p.403) |
| Gibbons (Hylobatidae) | Beck (1966) | Experimental study in captivity | Except for one individual, every other subject in the group was able to spontaneously solve all of the types of problems presented, and use string as a tool to retrieve the food | ‘The data clearly show that gibbons are able to solve the type of problem used by Kôhler (1959) to demonstrate insight. With one exception (every presentation of the Type II problem to LAF was discontinued) every animal was able to solve all of the types of problems presented[…]. A case of tool use may indeed be an insightfully learned behavioural sequence but it also may be one shaped by the patient application of operant techniques (in the wild by a fortuitous chain of environmental events) or it may even be a sequence which is not learned at all but rather transmitted genetically to the animal; for example shrikes’ using thorns on which to impale their prey’ (p106) |
| Gibbons (Hylobatidae) | Geissmann (2009) | Observational study in captivity | A captive female white-handed gibbon slammed the sliding door of her wooden sleeping box during the climax if a display bout | ‘In summary, the tool use in a female gibbon reported in this paper presents a singularity, as in several other reports on gibbon cognitive abilities’ (p.58) |
| Golden Lion Tamarins (Leontopithecus rosalia rosalia) | Stoinski & Beck (2001) | Observational study in captivity | Two types of tool use were observed in eight captive, free-ranging golden lion tamarins. All eight individuals used twigs and/or radio collar antennae to pry bark from trees and probe crevices, presumably for invertebrates. Three individuals used tools for grooming. Additionally, twigs were used as fishing tools in attempts to extract substances from tree holes or other crevices | ‘Social transmission may be one of the mechanisms responsible for the acquisition of tool use—six of the eight tool users resided in two social groups, and the only two individuals that used antennae as grooming tools were a bonded pair’ (p.319) |
| Japanese Macaques (Macaca Fuscata) | Leca, Gunst & Huffman (2010) | Observational study in the wild | The individual stretched one or a few pieces of its own hair or another individual’s hair and inserted the hair between the upper or lower front teeth by performing repeated teeth-chattering to remove food remains stuck between the teeth. So far, this behaviour has only been observed in one individual, and has not spread to the rest of the group | ‘Because chance may account for a good number of behavioural innovations (Reader & Laland, 2003), and DF was always associated with grooming activity, we suggest that the DF innovation is an accidental by-product of grooming’ (p.19) |
| Japanese Macaques (Macaca Fuscata) | Machida (1989) | Observational study in captivity | A juvenile female spontaneously began standing poles against a concrete wall and climbing up them, in the next couple of years the rest of the group started showing the same behaviour | ‘In a captive group of Japanese monkeys, a juvenile female spontaneously began standing poles against a concrete wall and climbing up them in 1983. By 1987, 3 juvenile females out of 39 monkeys had acquired the behaviour’ (p.1) |
| Japanese Macaques (Macaca fuscata) | Tokida et al. (1994) | Experimental study in captivity | The macaques used the hook tool, and one individual spontaneously threw stones into the tube to push the apple out of the other side of the tube. The same individual then coaxed her infants to go into the tube and retrieve the food | ‘Captive tufted capuchin monkeys, Cebus apella, learnt by trial and error within 2 h to use sticks to remove food from a transparent pipe, although Cebus seem to have a strong propensity for spontaneous tool use’ (p.1025) |
| Lion-Tailed Macaques (Macaca silenus) | Westergaard (1988) | Experimental study in captivity | Several macaques spontaneously manufactured and used tools to extract syrup from the apparatus | ‘This report is the first to describe spontaneous manufacture of tools in any group of Old World monkeys and provides evidence of greater continuity among primates for the expression of complex cognitive abilities. These data are consistent with hypotheses that lion-tailed macaques have extensive propensities for advanced sensorimotor skills and that omnivorous, extractive foraging is associated with the manufacture and use of tools’ (p.152) |
| Lion-Tailed Macaques (Macaca silenus) | Westergaard & Lindquist (1987) | Experimental study in captivity | Four macaques in the group created ladders by propping long pieces of browse or bamboo poles against vertical cage structures and climbing them | ‘Findings indicate richness in the frequency and form of manipulative activities, with juvenile males manipulating the test objects more frequently and exhibiting more goal-directed manipulative activity than adult females. A variety of goal-directed manipulative activities (use of objects to act as ladders, to apply leverage, and to create perches) occurred spontaneously, with some instances involving joint action or social use. These data are consistent with the hypotheses that macaques possess extensive capacities for object exploration and social facilitation, and that an evolutionary history of omnivorous foraging habits correlates positively with the expression of anomalous sensorimotor skills’ (p.1) |
| Long-Tailed Macaques (Macaca fascicularis fascicularis) | Watanabe, Urasopon & Malaivijitnond (2007) | Observational study in the wild | One macaque was observed using human hair as dental floss | ‘This behaviour could be considered a newly occurring cultural behaviour, which has become established under very specialised circumstances’ (p.1) |
| Long-Tailed Macaques (Macaca fascicularis fascicularis) | Zuberbühler et al. (1996) | Experimental study in captivity | One macaque spontaneously used a stick to rake in fruit. After a couple of years, five more individuals showed the same behaviour | ‘Since increased manipulations were only recorded at times when we caused tool-use behaviour in MD by presenting fruits, and since the manipulations were performed on the same object class MD was using as a tool, we conclude that MD’s activity was the cause for these increased activities’ (p.9) |
| Pig-tailed Macaques (Macaca nemestrina) | Chiang (1967) | Observational study in the wild | First observation of wild macaques using leaves to wash dirt/mud off seeds and fruit before eating them | No interpretation offered by the authors |
| Rhesus monkeys (Macaca mulatta) | Parks & Novak (1999) | Experimental study in captivity | Three females used a variety of cup-like containers as drinking utensils. All of the individuals used the trough to soak chow prior to ingestion | ‘In our study, female rhesus monkeys used objects for scooping and carrying water in a fashion similar to that described for capuchins. Some of our subjects drank from objects in the same way as that described for an adult male orangutan (Miller & Quiatt, 1983)-by scooping water into a hollow object and then raising the object to the mouth and drinking from it’ (p.22) |
| Tonkean Macaques (Macaca tonkeana) | Anderson (1985) | Experimental study in captivity | Two individuals spontaneously used the rod to retrieve the honey | ‘The results of the present study provide further evidence for the ability of macaques to spontaneously acquire new behavioural sequences involving object manipulation to obtain a goal such as food which is unattainable directly[…]The failure of the other members to acquire the new behaviour can be interpreted in terms of the conservatism of adults and the fact that the two adolescents tended to monopolise working with the rod once they had knowledge of its value’ (p.14) |
| Tonkean Macaques (Macaca tonkeana) | Ducoing & Thierry (2005) | Experimental study in captivity | Three out of the five subjects spontaneously used the wooden pole to retrieve the banana. The other two subjects never showed the behaviour | ‘In the first experiment, three males learned individually to obtain a food reward using a wooden pole as a climbing tool. They began using the pole to retrieve the reward only when they could alternatively experience acting on the object and reaching the target. In a second experiment, we first tested whether four other subjects could learn branch leaning after having observed a group-mate performing the task. Despite repeated opportunities to observe the demonstrator, they did not learn to use the pole as a tool. Hence we exposed the latter subjects to individual learning trials and they succeeded in the task’ (p.103) |
| Tonkean Macaques (Macaca tonkeana) | Ueno & Fujita (1998) | Observational study in captivity | One subject used a withered soft stalk of a coconut leaf to obtain a piece of food on the ground out of his reach | No interpretation offered by the authors |
| Tufted Capuchins (Cebus apella) | Fernandes (1991) | Observational study in the wild | A wild capuchin was observed opening oyster shells fixed to the mangrove by hitting them rapidly and repeatedly with a hand-held object which was a piece of the oyster colony itself | ‘C. apella is by far the most widely-distributed platyrrhine species and the behavioural adaptability of these capuchins, which enables them to exploit alternative resources in habitats, like the mangrove swamp, where typical primate foods such as fruit are relatively scarce, is undoubtedly a key factor in the ecological success of the species’ (p.530) |
| Tufted Capuchins (Cebus apella) | Ottoni & Mannu (2001) | Observational study in the wild | The group of capuchins was observed to start cracking nuts using two stones, one with a horizontal surface, laid on the substrate (the anvil) and the other, smaller, held in the hands (the hammer) | ‘As with chimpanzees, infant capuchins are highly tolerated by adults, and episodes involving the observation of older, more proficient individuals by younger ones, sometimes followed by manipulation of the stones by the youngster, point to a possibly role for some kind of observational learning, albeit restricted to stimulus enhancement, as a starting point of a long process of individual improvement by trial-and-error’ (p.357) |
| Tufted Capuchins (Cebus apella) | Struhsaker & Leland (1977) | Observational study in the wild | Three individuals were observed using stones to crack open encased palm nuts | ‘The exploitation of this abundant food resource by C. apella and not by any of the other seven sympatric primate species may give them a competitive advantage. This circumstance could partially account for the numerical superiority of C. apella at the time of our survey’ (p.1) |
| White-faced Capuchin (Cebus capucinus) | Boinski (1988) | Observational study in the wild | First observation of tool-use in white-faced capuchins. The monkey used a branch to repeatedly hit a venomous snake (Bothrops asper) | ‘This is the first direct observation of the use of a tool by a wild capuchin. Given the abundant evidence of tool use by capuchins in captivity, this anecdote is not very surprising. In an environment where appropriate stimuli are abundant, snake-bashing might have been discovered by a chance variation of a branch-shaking or a branch-throwing display’ (p.178) |
| Wild-bearded capuchins (Sapajus libidinosus) | Proffitt et al. (2016) | Observational study in the wild | Wild bearded capuchin monkeys in Brazil were observed deliberately break stones, unintentionally producing smaller fractured stones | ‘The capuchin data add support to an on-going paradigm shift in our understanding of stone tool production and the uniqueness of hominin technology. Within the last decade, studies have shown that the use and intentional production of sharp-edged flakes is not necessarily tied to the genus Homo. Capuchin SoS percussion goes a step further, demonstrating that the production of archaeologically identifiable flakes and cores, as currently defined, is no longer unique to the human lineage’ (p.3) |
| Birds | ||||
| Canaries (Serinus canaria) | Hinde & Warren (1959) | Experimental study in captivity | All the canneries spontaneously made nests indistinguishable to those of their wild counterparts | ‘Those birds which had material continuously, but were not permitted to construct a nest, built more actively than those allowed to build undisturbed. Birds without material for most of the time built vigorously during the watches with material, but seldom visited the nest-pan at other times. Birds without a nest-pan showed active building behaviour but it was mainly limited to the early phases of the nest-building sequence’ (p.1) |
| Goffin cockatoo (Tanimbar corella) | Auersperg et al. (2012) | Experimental study in captivity | One individual broke a large splinter off a beam outside of the enclosure, and then used the stick as a rake to retrieve the cashews and was successful in all 10 trials | ‘Our observations prove that innovative tool-related problem-solving is within this species’ cognitive resources. As it is unknown for tools to play a major role in this species’ ecology, this strengthens the view that tool competences can originate on general physical intelligence, rather than just as problem-specific ecological solutions’ (p.2) |
| Goffin cockatoo (Tanimbar corella) | Auersperg et al. (2016) | Experimental study in captivity | All the cockatoos were able to spontaneously make tools out of all the materials provided to retrieve the cashew nut | ‘We show that an Indonesian generalist parrot, the Goffins cockatoo, can flexibly and spontaneously transfer the manufacture of stick-type tools across three different materials. Each material required different manipulation patterns, including substrates that required active sculpting for achieving a functional, elongated shape’ (p.1) |
| Goffin cockatoo (Tanimbar corella) | Laumer et al. (2017) | Experimental study in captivity | The birds individually acquired the ability to bend hook tools from straight wire to retrieve food from vertical tubes and four subjects unbent wire to retrieve food from the horizontal tubes | ‘Pre-experience with ready-made hooks had some effect but was not necessary for success. Our results indicate that the ability to represent and manufacture tools according to a current need does not require genetically hardwired behavioural routines, but can indeed arise innovatively from domain general cognitive processing’ (p.1) |
| Hawaiian crows (Corvus hawaiiensis) | Rutz et al. (2016) | Experimental study in captivity | All the subjects in the group reliably and spontaneously used tools in all the extraction tasks provided | ‘This indicates that, despite considerable social mixing, it is unlikely that a single ‘innovation’ event can explain the observed species-wide distribution of tool competence. ‘Alalā clearly possess a propensity to ‘discover’ tool-assisted foraging solutions independently, which probably results from genetically canalised, persistent object-exploration behaviour’ (p.404) |
| Hyacinth macaws (Anodorhynchus hyacinthinus) | Borsari & Ottoni (2005) | Observational study in captivity | Six captive macaws were observed using wood as a lever to crack open nuts in their enclosure, similar to the behaviour they show in the wild | ‘Our data suggest that hyacinth macaws have an innate tendency to place objects (tools) and food together inside their beaks, while feeding. Four of our six subjects were captive bred, separated from their parents at hatching time and hand-raised, so they did not have the opportunity to watch a more experienced adult performing this behaviour. On the other hand, we cannot rule out the possibility that the younger juveniles could have learned to use tools from watching the older ones (nor that social learning could play a greater role in more naturalistic settings)’ (p.51) |
| New Caledonian Crow (Corvus moneduloides) | Hunt (1996) | Observational study in the wild | One of the first reports of hook tool-making of wild New Caledonian crows | ‘Crows have achieved a considerable technical capability in their tool manufacture and use’ (p.249) |
| New Caledonian Crow (Corvus moneduloides) | Kenward et al. (2005) | Experimental study in captivity | All the juvenile New Caledonian crows spontaneously manufactured and used tools, including the subjects that never had contact with adults of their species or any prior demonstration by humans | ‘In the light of our findings, it is possible that the high level of skill observed in wild adult crows is not socially acquired. Social input, however, may be important in transmitting specific techniques and tool shapes. This idea is supported by the close attention our juveniles paid to demonstrations of tool use by their human foster parents’ |
| ‘The fact that an inherited predisposition can account for a complex behaviour such as tool manufacture highlights the need for controlled investigation into behavioural ontogeny in other species that seemingly show culturally transmitted behaviour’ (p.121) | ||||
| New Caledonian Crow (Corvus moneduloides) | Taylor et al. (2007) | Experimental study in captivity | On their first attempt to solve the problem, six out of the seven naive crows used the short tool to probe the tool-box with the long tool, and then used the long tool to retrieve the baited food | ‘The experiments revealed that the crows did not solve the metatool task by trial-and-error learning during the task or through a previously learned rule. The sophisticated physical cognition shown appears to have been based on analogical reasoning. The ability to reason analogically may explain the exceptional tool-manufacturing skills of New Caledonian crows’ (p.1504) |
| New Caledonian Crow (Corvus moneduloides) | Taylor et al. (2010) | Experimental study in captivity | All the crows spontaneously solved the first task (pulling the string), however not all the subjects solved the task in the second experiment, and performance only increased with exposure | ‘However, when visual feedback was available via a mirror mounted next to the apparatus, two naïve crows were able to perform at the same level as the experienced group. Our results raise the possibility that spontaneous string pulling in New Caledonian crows may not be based on insight but on operant conditioning mediated by a perceptual-motor feedback cycle’ (p.1) |
| New Caledonian Crow (Corvus moneduloides) | Von Bayern et al. (2009) | Experimental study in captivity | Two subjects picked up stones and dropped them into the tube, despite having never used stones as tools or seen stones being dropped into the apparatus. The remaining two stone-naive subjects did not solve the task in the permitted time. However, one of them successfully used stones in a retest after having spontaneously pushed the platform with sticks in a stick/stone choice experiment | ‘Our results show that, for New Caledonian crows, learning about some functional affordances of the task (collapsibility of the platform through force or contact) is essential, whereas learning about specific visual stimuli (stones acting on the platform) or actions (picking up and dropping stones) is not’ (p.1) |
| New Caledonian Crow (Corvus moneduloides) | Weir (2002) | Experimental study in captivity | One female bent the wire to make a hook to retrieve the food in nine out of the ten valid trials | ‘Thus, at least one of our birds is capable of novel tool modification for a specific task. In the wild, New Caledonian crows make at least two sorts of hook tools using distinct techniques but the method used by our female crow is everyday physics (from their manipulative experience), but she had no model to imitate and, to our knowledge, no opportunity for hook-making to emerge by chance shaping or reinforcement of randomly generated behaviour’ (p.981) |
| New Caledonian Crow (Corvus moneduloides) and Kea parrots (Nestor notabilis) | Auersperg et al. (2011) | Experimental study in captivity | At least one individual of each species discovered all four available methods | ‘At least one individual of each species discovered all four available methods. This proves that in principle, the affordances of the tasks lay within the cognitive and physical capacity of both species’ (p.5) |
| Northern Blue Jays (Cyanocitta cristata) | Jones & Kamil (1973) | Observational study in captivity | Six captive blue-jays spontaneously crumpled newspaper that was in the enclosure to rake in pellets that were just outside of the enclosure | ‘Although a definitive answer is not possible, we feel that the behaviour was first acquired serendipitously by a single blue jay[…]The fact that to date we have found six jays in our colony demonstrating tool-using behaviour is thought to be more likely the result of the spread of the behaviour through observational learning or imitation than the result of the independent acquisition of this behaviour by each of the six jays’ (p.1087) |
| Pigeon (Columba livia domestica) | Epstein (1987) | Experimental study in captivity | All of the subjects pushed the provided box under the banana to retrieve it | ‘Here we appear to have on hand an instance of insightful problem solving’ (p.62) |
| Rooks (Corvus frugilegus) | Bird & Emery (2009a) | Experimental study in captivity | All the naive rooks made, used and modified different tools (stones, sticks, hooks) spontaneously to retrieve the worm | ‘The initial solution to the task may have been derived from the birds’ prior experience. Seemingly insightful behaviours may be achieved by ‘‘chaining’’ previously rewarded behaviours or by generalising from one task to another. Although the subjects’ behaviour can be explained in these ways, there is some reason to suggest that the behaviour was not solely a conditioned action: multiple acts of stone dropping were necessary for success (in previous experiments, one stone had been necessary for success), and subjects did not try to reach for the reward after dropping each stone. In addition, they reached for the worm from the top of the tube rather than checking at the base (in previous experiments, the worm was accessible below the tube)’ (p.1411) |
| Rooks (Corvus frugilegus) | Bird & Emery (2009b) | Experimental study in captivity | All four subjects solved the task and spontaneously started using stones to raise the water level to a height at which the worm could be reached | ‘It is possible that the initial stone-dropping behaviour was elicited by subjects’ previous experience and that the increased proximity of the worm reinforced the initial stone drop, leading to a cycle of stone dropping until the worm could be reached. However, it is not clear that the worm getting closer would seem rewarding to the subject. Rather, the worm getting closer but still not being within reach might equally have been unrewarding or frustrating; hence, the behaviour would be repeated only if it were goal directed’ (p.1141) |
| Rooks (Corvus frugilegus) | Seed et al. (2006) | Experimental study in captivity | All the rooks spontaneously used sticks in the trap-tube task to pull the food towards them | ‘One possibility for this is the fact that, although they are not tool-users, rooks are the only corvids reported to cache food by digging a hole before placing the food inside it and then covering it over. Given that the traps are effectively holes, it may be that learning what constitutes a functional hole is an ecologically relevant problem for a rook. Corvids are also opportunistic generalists for whom rapid learning is likely to confer a high survival advantage. Other possible explanations for this difference may be considered: Shettleworth has pointed out that many of the primates used in similar experiments have participated in a variety of other physical tasks (unlike our rooks), which could have interfered with their learning; secondly, the rooks were not required to insert a tool, and this could also potentially facilitate learning on the task; lastly, it is possible that pulling food toward oneself is a more natural behaviour for animals than pushing it away, and this improvement in ‘‘external validity’’ may also be a facilitatory factor’ (p.700) |
| Rooks (Corvus frugilegus) | Tebbich et al. (2006) | Experimental study in captivity | All the rooks used the stick provided in the apparatus to retrieve the food | ‘This study demonstrates that rooks, which do not spontaneously use tools, can solve the trap-tube problem. Our findings are in line with those of Hauser and colleagues (Hauser, Krali & Botto-Mahan, 1999; Hauser, Pearson & Seelig, 2002), who have found that non-tool-using primates are capable of learning the solution to other physical problems, such as those based on connectedness’ (p.229) |
| Woodpecker finch (Cactospiza pallida) | Tebbich & Bshary (2004) | Experimental study in captivity | One of six woodpecker finches was able to solve the trap tube task, and several individuals modified tools and chose twigs of appropriate length | ‘Tool use in the woodpecker finch is not a stereotypic behavioural pattern, but is open to modification by learning[…]Tool use in the woodpecker finch also seems to be guided by a rapid process of trial and error learning’ (p.8) |
| Woodpecker finch (Cactospiza pallida) | Tebbich et al. (2001) | Experimental study in captivity | One individual in the no-model group started using tools during testing conditions | ‘However, we found that not all adult woodpecker finches used tools in our experiments. These non-tool-using individuals also did not learn this task by observing tool-using conspecifics. Our results suggest that tool-use behaviour depends on a very specific learning disposition that involves trial-and-error learning during a sensitive phase early in on in ontogeny’ (p.2189) |
| Other Animals | ||||
| Asian Elephant (Elephas maximus) | Chevalier-Skolnikoff & Liska (1993) | Experimental study in captivity | 21 different types of spontaneous tool-use were observed in the captive groups of elephants, when the elephants were provided with more tools in their enclosure. Most behaviours involved using tools (such as sticks and leaves) for body-care purposes | ‘Tool use in elephants occurs mainly in the contexts of body care, parasite control and body cooling, and may reflect an adaptive function in these nearly furless land mammals’ (p.217) |
| Asian Elephant (Elephas maximus) | Foerder et al. (2011) | Experimental study in captivity | One elephant showed spontaneous problem solving by moving a large plastic cube, on which he then stood, to acquire the food. In further testing he showed behavioural flexibility, using this technique to reach other items and retrieving the cube from various locations to use as a tool to acquire food | ‘These results provide experimental evidence that an elephant is capable of insightful problem solving through tool use. Evidence for this ability is indicated by the suddenness of Kandula’s problem solving behaviour without evidence of prior trial and error learning’ (p.3) |
| Bear (Ursos arctos) | Deecke (2012) | Observational study in the wild | One bear was observed picking up barnacle-encrusted rocks in shallow water, manipulating them, re-orienting them in its forepaws, and then using them to rub its neck and muzzle | ‘However, social learning may not be necessary to explain the spread of stone-rubbing even if this form of tool-use was found to be common: brown bears frequently turn over rocks in search of food and feed on intertidal barnacles…both of which would provide ample opportunity for the acquisition of stone-rubbing behaviour through individual learning alone’ (p.7) |
| Bear (Ursos arctos) | Waroff et al. (2017) | Experimental study in captivity | Six out of the eight tested bears manipulated and used objects to climb on top of to reach suspended food | ‘Our observations in captive bears reveal that bears very often use physical force when approaching new problems which will lead to trial and error problem-solving…When force does not work, bears often appear to demonstrate insight like behaviour, with individual variability’ (p. 63) |
| Dingo (Canis dingo) | Smith, Appleby & Litchfield (2011) | Observational study in captivity | A captive male dingo spontaneously learned to move objects around his enclosure, apparently to multiple ends, such as in an effort to gain the additional height required to attain objects otherwise out of reach, or to attain a better view of his surroundings | ‘These behaviours may have emerged as a result of simple learning processes and reinforcement rather than by forming an ‘insightful solution’ (as suggested by Köhler for chimpanzees who displayed similar behaviours, 1927/1971; for criticisms of insight learning see Windholz & Lamal, 1985). It is therefore possible that dingoes, like other wild canids (e.g. coyotes, Coppinger & Coppinger, 2001; wolves, Mech, 1991) appear to be able to replicate behaviours performed by sanctuary staff as a result of observational learning (e.g. wolves, Frank, 1980). Through trial-and-error (or ‘trial-and-success’) learning (Thorndike, 1898; Chance, 1999) or observational learning (Bandura, 1965) with Sanctuary staff serving as observable models by moving objects during routine enclosure maintenance, Sterling may have formed complex associations and applied them to different contexts (escape, view, or attain objects out-of-reach)’ (p.223) |
| Octopus (Amphioctopus marginatus) | Finn, Tregenza & Norman (2009) | Observational study in the wild | Wild octopus was observed carrying around two coconut halves that were then used as a defensive protective shell when needed | ‘The behaviour reported here is likely to have evolved using large empty bivalve shells prior to the relatively recent supply of the clean and light coconut shell halves discarded by the coastal human communities adjacent to the marine habitat of this species’ (p.2) |
| Sea Otter (Enhydra lutris nereis) | Nicholson et al. (2007) | Observational study in captivity | Orphaned sea otters in a research facility spontaneously developed rudimentary pound hammering behaviours to open encased food | ‘Pounding open clams was positively correlated with biting open mussels, so rehabilitation methods had a similar effect on the development of this milestone. Surrogate-reared pups, therefore, developed all foraging skills at a significantly younger age (by 2–3 weeks) than non-surrogate-reared pups and an age similar to their wild counterparts’ (p.316) |