Table 1. Non-cognitive internal (subject-related) and external (testing-related) factors potentially affecting cognitive performance (in physical cognition tasks).
Increase (↑), decrease (↓) or no effect (=) on performance.
| Factor | Cognitive task(s)/skills | Effect on performance? | Species | Reference |
|---|---|---|---|---|
| Trait anxiety | Reversal learning | Performance ↓ in subjects with trait anxiety | Long-tailed macaques (Macaca fasciularis) | Toxopeius et al., 2005 |
| Temperament | Physical cognition | Performance ↑ in bolder subjects | Chimpanzees (Pan troglodytes) & orangutans (Pongo pygmaeus) | Herrmann et al., 2007 |
| Personality | Training | Performance ↑ in subjects with high openness & low assertiveness scores | Brown capuchins (Sapajus apella) | Morton et al., 2013 |
| Emotional reactivity | Object permanence | Participation ↓ but performance = in subjects with elevated arousal levels during testing |
Common marmosets (Callithrix jacchus) | Schubiger et al., 2015 |
| Hand preference | Problem solving | Exploration ↑ in subjects with a right-hand preference but performance = in right-handed and left-handed marmosets |
Common marmosets (Callithrix jacchus) | Cameron & Rogers, 1999 |
| Cognitive bias | Negative cognitive bias (↓ exploration of an ambiguous test stimulus) in left-handed but not right-handed subjects | Gordon & Rogers, 2015 | ||
| Rearing conditions | Repertoire of learned cognitive skills |
1. Skill repertoire ↑ in mother-reared individuals 2. Skill repertoire ↓ in orphaned individuals |
Various primate species | Reviewed in: van Schaik & Burkart, 2011 |
| Set of skills & learning speed ↑ in enculturated individuals; even beyond a species’ natural repertoire | Great apes | |||
| Degree of orientation towards humans | Problem-solving | Performance ↑ in subjects with high HOI (Human-Orientation Index) | Sumatran (Pongo abelii) & Bornean orangutans (Pongo pygmaeus) |
Damerius, Forss et al., 2017 |
| Human care & social housing with conspecifics | Inhibitory control, reversal learning, problem solving, causal reasoning |
Performance ↑ with curiosity & exploration (“curious response-and-exploration style”) | Damerius et al., 2017 | |
| Task format |
Quantity discrimination | Performance ↑ 1. with inedible test stimuli 2. with edible test stimuli if reward items differ in food type |
Olive baboons (Papio anubis) & long-tailed macaques (Macaca fascicularis) | Schmitt et al., 2011 |
| Performance ↑ with edible test stimuli | Brown capuchins (Cebus sapajus apella) | Gazes et al., 2017 |
||
| Performance ↑ with rewards of higher value | Brown capuchins (Cebus sapajus apella) & common squirrel monkeys (Saimiri sciureus) | |||
| Memory | 1. Performance ↑ with more choice options (9 instead of 2) 2. Performance ↓ with delay duration (in line with forgetting curve) |
Common squirrel monkeys (Saimiri sciureus) & common marmosets (Callithrix jacchus) | Schubiger et al., 20161 | |
| Visual object discrimination | Performance ↑ when tactile exploration of the objects is possible | Capuchin monkeys (Sapajus spp.) | Carducci et al., 2018 | |
| Opportunistic testing |
Inhibitory control & memory | Performance = when excluding subjects who take longer to complete all test trials |
Common marmosets (Callitrix jacchus) & squirrel monkeys (Saimiri sciureus) | This study |
| Quantity discrimination & reversal learning | Common marmosets (Callithrix jacchus) |
1see [26] for a similar positive effect of more choice options in an object choice task)