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. Author manuscript; available in PMC: 2017 May 1.
Published in final edited form as: Psychol Aging. 2016 Mar 7;31(3):249–254. doi: 10.1037/pag0000077

Effects of Age and Environmental Support for Rehearsal on Visuospatial Working Memory

Lindsey Lilienthal 1, Sandra Hale 1, Joel Myerson 1
PMCID: PMC4923937  NIHMSID: NIHMS764886  PMID: 26950223

Abstract

The present study investigated whether older adults’ visuospatial working memory shows effects of environmental support for rehearsal similar to those observed in young adults (Lilienthal, Hale, & Myerson, 2014). When the duration of inter-item intervals was 4 s and participants had sufficient time to rehearse, location memory spans were larger in both age groups when environmental support was present than when support was absent. Critically, however, the age-related difference in memory was actually larger when support was provided, suggesting that young and older adults may differ in their rehearsal of to-be-remembered locations.

Keywords: visuospatial working memory, environmental support, age differences, aging

The amount of support for cognitive processing provided by the environment is widely believed to be an important determinant of memory performance (e.g., Craik, 1994; Craik & Jennings, 1992; Lindenberger & Mayr, 2014). The term environmental support originally was used to describe situations in which the context present at the time of retrieval was similar to the context that had been present at encoding, thereby reducing the need for self-initiated, effortful processing during retrieval. For example, recognition tasks tend to provide more environmental support than recall tasks because participants are able to rely more heavily on cues present in the environment at retrieval, decreasing the need for active reconstruction (e.g., Craik, 1986; Craik & McDowd, 1987).

Most research on environmental support has examined its effects on verbal memory, but a few studies have extended the concept to the visuospatial domain, using the term to describe several different manipulations of visuospatial memory materials. For example, Smith, Park, Cherry, and Berkovsky (1990) manipulated environmental support by varying the amount of visual detail and propositional content present in to-be-remembered pictures, and Sharps and Gollin (1987) manipulated environmental support by varying the complexity of the environment in which to-be-remembered location-object pairs were placed (see also Park, Cherry, Smith, & Lafronza, 1990). Each of these studies reported that visuospatial memory was generally better in situations in which support was presumed to be greater.

It has been suggested that the presence of environmental support during memory tasks may be particularly beneficial for older adults because they have a specific deficit in self-initiated processing (e.g., Craik, 1994; Hasher & Zacks, 1979). Lindenberger and Mayr (2014) recently highlighted the need to pay closer attention to the shift from self-initiated processing to reliance on external cues that is hypothesized to underlie the differential benefits of environmental support in order to design more aging-friendly environments. Consistent with this hypothesized shift, a number of studies, including some conducted using visuospatial materials, have found that the presence of environmental support reduced or eliminated age-related differences in memory (e.g., Craik & McDowd, 1987; Sharps & Gollin, 1987; Smith et al., 1990; for a review, see Morrow & Rogers, 2008). For example, Smith et al. found that although young adults were better than older adults at correctly recognizing pictures for which environmental support at encoding was presumed to be low, the age-related difference was eliminated for pictures for which environmental support was high (although it should be noted that some studies of environmental support report an opposite pattern; e.g., Cherry & Park, 1993; Craik & Byrd, 1982; Park et al., 1990).

Most of the previous research on environmental support in memory tasks has investigated support for encoding and/or retrieval. Lilienthal, Hale, and Myerson (2014) extended the concept of environmental support to visuospatial rehearsal, a process that is thought to involve eye movements and/or attention shifts to to-be-remembered locations (e.g., Awh, Jonides, & Reuter-Lorenz, 1998; Godijn & Theeuwes, 2012; Tremblay, Saint-Aubin, & Jalbert, 2006). When memory tasks include an interpolated secondary task or lists of more than four to-be-remembered items, it is widely assumed that to-be-remembered items are displaced from primary memory and, at test, must be retrieved from secondary memory (e.g., Unsworth & Engle, 2007). Importantly, McCabe (2008) reported that when participants were given opportunities to rehearse during a verbal working memory task, retrieval from secondary memory was improved, perhaps because rehearsal served as a form of retrieval practice. It follows that if environmental support influences how effectively participants can rehearse, or the likelihood that they will do so, then environmental support also should have important effects on visuospatial memory performance.

Accordingly, Lilienthal et al. (2014) investigated whether visuospatial rehearsal, and thus visuospatial memory, was affected by the presence or absence of environmental support during inter-item intervals. In two experiments, when environmental support was present (i.e., participants viewed the array of possible locations during inter-item intervals), young adults’ memory spans were significantly larger with long (4.0 s) inter-item intervals than with short (1.0 s) intervals, whereas when environmental support was absent (i.e., participants viewed a blank screen during inter-item intervals), memory spans were significantly smaller with long inter-item intervals. Based on these results, Lilienthal et al. concluded that rehearsal of to-be-remembered locations using eye movements or shifts of attention can prevent forgetting, and perhaps even improve memory performance, but only when environmental support for rehearsal is provided.

The present study represents the first investigation of the effects of environmental support for visuospatial rehearsal on age-related differences in visuospatial memory. The goal of the study was to determine whether Lilienthal et al.’s (2014) conclusions also apply to older adults. Young and older adults completed a location memory task in which both inter-item interval duration (short versus long) and environmental support during inter-item intervals (present versus absent) were manipulated, as in Lilienthal et al. If environmental support for the rehearsal of visuospatial information differentially benefits older adults, age-related differences in memory span should be smallest when environmental support is present. Such a finding could have important implications because although age-related differences are observed on a wide variety of working memory tasks, the largest reported differences typically are observed on tasks involving memory for visuospatial information (e.g., Hale et al., 2011; Jenkins, Myerson, Joerding, & Hale, 2000; Myerson, Emery, White, & Hale, 2003).

Method

Participants

Participants were twenty-four young adults (16 female; age M = 19.0, SD = 1.0, range = 18–21) and 24 older adults (20 female; age M = 75.0, SD = 7.0, range = 66–87). The young adults were undergraduate students at Washington University in St. Louis who participated as partial fulfillment of a course requirement. The older adults were community-dwelling residents of the St. Louis area who participated in exchange for monetary compensation. Older adults were screened for cognitive impairment using the Telephone Interview for Cognitive Status, which correlates highly with other common screening instruments but does not require face-to-face administration (Brandt, Spencer, & Folstein, 1988), as well as for significant health issues (e.g., stroke, Parkinson’s disease). The average number of years of education was 12.9 years (SD = 1.0) for young adults and 16.1 years (SD = 3.6) for older adults. All participants reported normal or corrected-to-normal visual acuity and English as their native language.

Materials and Procedure

In a single experimental session that lasted approximately 1.5 hours, each participant performed four conditions of a visuospatial simple span task (see Figure 1) that were largely identical to the task conditions used by Lilienthal et al. (2014) in their Experiment 1. In each of the four conditions, participants were shown an array of 30 circles on a computer screen. Each circle was 1.0 cm in diameter, and the average distance between the centers of the circles in the array was 1.75 cm. The circles were arranged so that the array appeared unstructured, and the configuration of the array was changed on each trial (i.e., a different set of 30 locations was presented on each trial). Then, on every trial, a subset of the circles turned red one at a time and participants were instructed to remember the locations of the red circles. Each red circle (i.e., each to-be-remembered location) was presented for 1.0 s, followed by an inter-item interval that was either 1.0 s or 4.0 s (i.e., either short or long), depending on the condition. Following presentation of all the to-be-remembered locations for that trial, participants were asked to recall as many of the locations as possible. More specifically, participants again were presented with the same array of 30 circles, now appearing on a gray background, and were asked to use the computer mouse to click on the circles that had turned red during that trial. Participants were allowed to recall the locations in any order, taking as much time as they needed, and were instructed to click on an icon labeled “Done” when they were finished.

Figure 1.

Figure 1

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Example trials with a list length of two from the task conditions with and without environmental support. Inter-item intervals were either short or long (1.0 s or 4.0 s, respectively).

Each of the four conditions began with four practice trials, followed by 22 test trials. List lengths (i.e., the number of to-be-remembered locations on the trial) in each of the four conditions ranged from one to 11, and participants completed two trials at each length, for a total of 22 test trials. List lengths were presented in ascending order, so that participants first performed the two trials with a list length of one, followed by two trials with a list length of two, and so on. As in Lilienthal et al. (2014), memory performance was assessed in each condition using a span measure, or one less than the shortest list length at which both test trials were incorrect. It should be noted, however, that the pattern of results did not change when a partial span measure (Hale et al., 2011) was used instead.

Across the four conditions, two aspects of the inter-item intervals were manipulated: The duration of the intervals was either short or long (i.e., 1.0 s or 4.0 s), and environmental support during the intervals was either present or absent. When environmental support was present, the array of 30 circles remained visible on the computer screen during inter-item intervals, whereas when environmental support was absent, participants instead viewed a blank screen (see Figure 1). Thus, one condition had short inter-item intervals with environmental support present, one condition had short inter-item intervals with environmental support absent, one condition had long inter-item intervals with environmental support present, and one condition had long inter-item intervals with environmental support absent. All participants completed all four task conditions, and so the manipulations of environmental support and inter-item interval duration were both within-subjects’ manipulations.

The order of the four task conditions was counterbalanced across participants, so that each participant performed the conditions in one of four orders (with six participants in each age group in each order condition). Half of the participants completed the two conditions with environmental support present followed by the two conditions with environmental support absent, and the other half of the participants completed the conditions in the opposite order. Within each of these two groups of participants, half completed a condition with short inter-item intervals first, and the other half completed a condition with long inter-item intervals first; however, the interval durations were always presented alternately (i.e., either short-long-short-long or long-short-long-short).

Results

Young and older adults’ memory spans in each task condition are presented in Figure 2. A 2 (environmental support: present vs. absent) × 2 (inter-item interval duration: short vs. long) × 2 (age group: young vs. old) ANOVA revealed a main effect of age group, F(1, 46) = 46.4, p < .001, partial η2 = .50, reflecting the fact that young adults’ spans were larger than older adults’ spans. In addition, there was a main effect of environmental support, F(1, 46) = 37.2, p < .001, partial η2 = .45, but no effect of interval duration, F(1, 46) = 2.3, ns; however, these results must be interpreted in light of the significant interaction between support and interval duration, F(1, 46) = 24.5, p < .001, partial η2 = .35. This two-way interaction reflects the fact that, as may be seen in Figure 2, spans were smaller when inter-item intervals were long compared to when intervals were short, but only when environmental support was absent.

Figure 2.

Figure 2

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Memory spans for young and older adults in all four task conditions. The short and long inter-item intervals were 1.0 s and 4.0 s in duration, respectively. Error bars represent the standard error of the mean.

Importantly, the ANOVA also revealed a significant three-way interaction between environmental support, inter-item interval duration, and age group, F(1, 46) = 4.5, p = .039, partial η2 = .09. Planned comparisons revealed that when environmental support was absent, both young and older adults had significantly smaller spans when inter-item intervals were long compared to short: for young adults, t(23) = 5.0, p < .001; for older adults, t(23) = 2.1, p = .047. When environmental support was present, however, young adults had significantly larger spans when inter-item intervals were long, whereas older adults’ spans did not differ across inter-item interval conditions: for young adults, t(23) = 2.1, p = .045; for older adults, t(23) = 1.2, ns.

To specifically address whether the presence of environmental support reduced age-related differences in memory span, a 2 (environmental support) × 2 (age group) ANOVA was performed on spans only from the conditions with long inter-item intervals. Significant main effects of both environmental support, F(1, 46) = 55.2, p < .001, partial η2 = .55, and age group, F(1, 46) = 28.7, p < .001, partial η2 = .39, were revealed. However, these effects must be interpreted in light of the significant two-way interaction between support and group, F(1, 46) = 5.1, p = .028, partial η2 = .10. When inter-item intervals were long, spans in both age groups were significantly larger when environmental support was present compared to when support was absent: for young adults, t(23) = 6.6, p < .001; for older adults, t(23) = 3.8, p < .001. Notably, similar percentages of participants in both age groups showed an increase in span when environmental support was present (79% of young adults and 71% of older adults), but it was the young adults who showed larger benefits of the presence of environmental support. More specifically, the difference in memory span between young and older adults was 0.87 locations when support was absent, but this difference increased to 1.75 when support was present (in Figure 2, compare the difference between the spans indicated by the two white triangles to the difference indicated by the two black triangles).

Discussion

The present study is the first to directly investigate the effects of environmental support for rehearsal on older adults’ visuospatial memory spans. Young and older adults performed four conditions of a visuospatial memory span task that varied in inter-item interval duration as well as in whether or not environmental support for rehearsal was provided during those intervals. When support was absent, memory spans in both age groups were larger when the intervals were brief and smaller when the intervals were long. When environmental support was present, however, young adults’ spans were larger when intervals were long, whereas older adults’ spans did not vary significantly with inter-item interval duration.

Importantly, both young and older adults benefited from environmental support when inter-item intervals were long, but the age-related difference in memory span was approximately twice as large when support was present than when it was absent, indicating that the young adults actually benefited more from environmental support for rehearsal than the older adults. This finding is clearly inconsistent with the commonly held belief that environmental support reduces age-related differences. It should be noted, however, that environmental support does not always reduce age differences (for a review, see Morrow & Rogers, 2008), and older adults may differentially benefit from support only when it reduces effortful processing (e.g., Craik & Byrd, 1982). Even if support encouraged rehearsal in the present study, it may not have reduced the effort required, and it is possible that this is the reason why older adults did not benefit more than young adults.

Most previous research on age-related differences in the effects of environmental support has focused on support during encoding and retrieval. The present study, in contrast, sought to extend the environmental support concept to a new area: rehearsal on visuospatial span tasks. Our results suggest there may be significant age-related differences in visuospatial rehearsal and raise a number of interesting issues. For example, even when provided with support, older adults may rehearse locations less, or less effectively, than young adults. Visuospatial working memory declines at approximately twice the rate of verbal working memory on both laboratory tasks (e.g., Hale et al., 2011) and standardized span measures (Myerson et al., 2003), and it is possible that age-related differences in rehearsal play a role in this differential decline.

Moreover, visuospatial spans appear to decline continuously with age (e.g., Hale et al., 2011), and it would be of interest to know if the amount of benefit from environmental support in “young older adults” differs from that in “old older adults,” as might be expected if rehearsal plays an important role in this decline. Further, older adults may be at a disadvantage when to-be-remembered series are presented in order of increasing difficulty (e.g., Lustig, May, & Hasher, & 2001; Rowe, Hasher, & Turcotte, 2008), as in the current study, and thus it also would be of interest to know whether presentation format affects the benefits older adults receive from environmental support for rehearsal. Finally, future research should address whether the presence of environmental support for rehearsal influences whether people represent to-be-remembered locations in a global or configural way (e.g., Taylor, Thomas, Artuso, & Eastman, 2014), and if so, whether there are any age-related differences in this regard.

The present finding that in the absence of environmental support, both young and older adults’ visuospatial spans decreased with increases in the duration of inter-item intervals suggests that the observed forgetting occurred because without support, the likelihood and/or effectiveness of rehearsal was reduced. Moreover, participants did not perform any secondary task during inter-item intervals, making it unlikely that this forgetting was due to interference. Instead, the present results provide evidence that decay contributes to forgetting on visuospatial span tasks. Interestingly, models of working memory that posit a role for decay do not necessarily predict forgetting like that observed in the present study, as well as in Lilienthal et al. (2014), which used similar procedures. For example, the time-based resource-sharing model (e.g., Barrouillet, Bernardin, & Camos, 2004) posits that forgetting occurs when attention is diverted from refreshing memory traces, but participants in the present study were always free to rehearse and/or refresh the to-be-remembered locations. Although the time-based resource-sharing model does not explicitly predict what will occur when attention is available, exactly how and when forgetting might occur under such circumstances is unclear.

The finding that when environmental support was present, young adults’ location memory spans actually increased with increases in the duration of inter-item intervals replicates Lilienthal et al. (2014) and strongly suggests that environmental support can facilitate rehearsal of to-be-remembered locations. Moreover, this finding is consistent with McCabe’s (2008) idea that rehearsal of to-be-remembered items during a working memory task can serve as a form of retrieval practice, thereby improving recall. Importantly, McCabe’s study focused on verbal working memory, whereas the present results suggest that for visuospatial items, environmental support is needed in order for rehearsal to increase memory spans.

Finally, we would note what appears to be a growing realization in aging research that multiple mechanisms underlie many important cognitive phenomena, as revealed by the way in which age-related differences vary across tasks and contexts (Lustig & Jantz, 2015; Morrow & Rogers, 2008). For example, Lustig and Jantz suggested that in order to understand the mechanism(s) underlying age-related differences in interference control, one should not ask simply whether such differences exist, but rather when are such differences observed and how do they arise. We strongly agree, and believe that a similar situation may exist with respect to both environmental support and working memory. That is, the results of the present study should be viewed as part of a larger pattern of age-related differences on working memory tasks that reveals complex relations between age, environmental support, and memory domain on different tasks and in different contexts.

For example, Oberauer and Lewandowsky have argued repeatedly (e.g., Lewandowsky, Oberauer, & Brown, 2009; Oberauer & Lewandowsky, 2008; cf., Barrouillet, Portrat, Vergauwe, Diependaele, & Camos, 2011), based largely on studies of working memory for verbal information, that forgetting is the consequence of interference rather than decay. As already noted, however, the present findings reveal that, in the absence of environmental support for visuospatial rehearsal, decay also plays a role. Moreover, Lilienthal et al. (2014) found that temporal distinctiveness did not contribute significantly to the time-based forgetting observed on a visuospatial span task similar to that in the present study (see also, Ricker, Spiegel, & Cowan, 2014), contrary to what is observed with forgetting on verbal working memory tasks. These findings, taken together with fact that visuospatial span declines approximately twice as fast with age as verbal span (Hale et al., 2011; Myerson et al., 2003), indicate that age-related differences in working memory reflect domain-specific as well as domain-general mechanisms.

Acknowledgments

This research was supported by NIA Training Grant AG00030.

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