Working memory, or the ability to maintain and manipulate information in mind when it is no longer physically present, is a pervasive yet severely capacity-limited component of cognition. Visual working memory, also known as visual short-term memory (VSTM), is limited to three or four items on average, with individual differences that range from roughly two to up to six items. Despite agreement that capacity is functionally limited, the current literature is split with respect to the nature of VSTM representations on two key questions: (1) What information is maintained in VSTM? (2) How is information stored in VSTM? The studies presented here address these questions using an event-related potential (ERP) task and a series of behavioural experiments that incorporate attentional selection via retrospective cueing (retro-cues). Experiment 1 manipulated both the number of features and the number of locations to be remembered in a lateralized change-detection task, with differences in the amplitude and topography of the resulting contralateral delay activity (CDA) indicating separate stores for features and locations. Experiments 2a-c established the basic effects of retro-cues on change-detection tasks, showing that attentional selection operated on one system at a time, with overall shorter response times and increased capacity estimates once baseline capacity was exceeded. Experiments 3a-b demonstrated that retro-cues biased VSTM resources to the cued item at the expense of representational strength of the other, non-cued items, showing flexible reallocation of resources. Experiments 4a-b presented multiple retro-cues to further examine the flexible reallocation of resources in VSTM, showing that capacity benefits depended on spatial specificity of retro-cues and that VSTM weights could be reallocated multiple times before probe comparison. Experiment 5 discounted the potential role of a general alerting mechanism in boosting capacity estimates, showing again that the retro-cue benefit required specificity of the cue. Experiment 6 showed that flexible reallocation of resources within one system did not change the online maintenance of representations within the other system. Thus, the studies collectively address the questions of (1) what and (2) how information is stored by supporting a two-system model of VSTM in which (1) locations and features are stored (2) independently via flexibly allocated resources.

Working memory, or the ability to maintain and manipulate information in mind when it is no longer physically present, is a pervasive yet severely capacity-limited component of cognition. Visual working memory, also known as visual short-term memory (VSTM), is limited to three or four items on average, with individual differences that range from roughly two to up to six items. Despite agreement that capacity is functionally limited, the current literature is split with respect to the nature of VSTM representations on two key questions: (1) What information is maintained in VSTM? (2) How is information stored in VSTM? The studies presented here address these questions using an event-related potential (ERP) task and a series of behavioural experiments that incorporate attentional selection via retrospective cueing (retro-cues). Experiment 1 manipulated both the number of features and the number of locations to be remembered in a lateralized change-detection task, with differences in the amplitude and topography of the resulting contralateral delay activity (CDA) indicating separate stores for features and locations. Experiments 2a-c established the basic effects of retro-cues on change-detection tasks, showing that attentional selection operated on one system at a time, with overall shorter response times and increased capacity estimates once baseline capacity was exceeded. Experiments 3a-b demonstrated that retro-cues biased VSTM resources to the cued item at the expense of representational strength of the other, non-cued items, showing flexible reallocation of resources. Experiments 4a-b presented multiple retro-cues to further examine the flexible reallocation of resources in VSTM, showing that capacity benefits depended on spatial specificity of retro-cues and that VSTM weights could be reallocated multiple times before probe comparison. Experiment 5 discounted the potential role of a general alerting mechanism in boosting capacity estimates, showing again that the retro-cue benefit required specificity of the cue. Experiment 6 showed that flexible reallocation of resources within one system did not change the online maintenance of representations within the other system. Thus, the studies collectively address the questions of (1) what and (2) how information is stored by supporting a two-system model of VSTM in which (1) locations and features are stored (2) independently via flexibly allocated resources.

Visual long term memory (VLTM) research has shown that we are capable of learning a virtually infinite amount of visual information. At the same time, visual short term memory (VSTM) research has shown that there is a severe limitation in the amount of information we can simultaneously apprehend at a given time. How does the severe capacity limitation in the initial uptake of information influence the encoding of information into VLTM? To this date, there has been no direct test of such influence, and the effect of such limitation has been unclear. Here, we demonstrate that, across wide varieties of conditions, the severe-capacity limitation in VSTM dictates the encoding of information into VLTM by determining the "bandwidth" of information transfer. This finding has a substantial implication for the understanding of the role of severely-capacity limited VSTM in forming many types of VLTM representations. / 10000-01-01

Anxiety is of importance within the field of cognition because it is often associated with adverse effects on attention, information processing, learning and memory (Eysenck, 1992, 2007). In existing literature, it has been reported that trait anxiety hinders cognitive performance (i.e., working memory capacity WMC). However, the relationship between trait anxiety and cognitive performance might be moderated by working memory capacity (WMC). For example, Owens (2014) reported that trait anxiety was negatively correlated with cognitive performance in the low WMC group and positively correlated to cognitive performance in the high WMC group. Although, past research on the working memory system has focused on the impairments that are triggered by trait anxiety, there may be an exception to these existing findings. Recently, Moriya & Sugiura (2012, 2018) reported that high trait anxiety paradoxically enhances visual-short term memory capacity (VSTMC). In this present study, we sought to identify if WMC modulates the relationship between trait anxiety and VSTM performance. Our first hypothesis stated that there would be a positive correlation between trait anxiety and VSTM capacity. Our second hypothesis stated that the correlation between trait anxiety and VSTM capacity would be modulated by WMC. In this current study, working memory, visual-short term memory and self‐report levels of trait anxiety, were evaluated. The results of the current study did not provide strong support for neither of our hypotheses. For hypothesis 1, we were not able to replicate Moriya and Sugiura’s findings; trait anxiety did not enhance VSTM performance. For hypothesis 2, VSTM performance was not influenced by the interaction term of WMC x trait anxiety; in such WMC and trait anxiety combined were unrelated to VSTM performance. Despite this work, we are still somewhat unclear whether trait anxiety enhances VSTM performance. Although, our data did not provide definitive support for enhanced VSTMC in high trait anxious individuals it did provide three unique findings. First, our results suggest that the level of WMC does in fact modulate the relationship between trait anxiety and VSTMC. Second, only the somatic component of trait anxiety was negatively correlated to VSTM performance for LWMC individuals. Third, WMC and VSTMC were significantly associated with one another. In closing, our three core findings may provide important insights towards improving future research when assessing the relationship between trait anxiety and VSTM performance.

Since antiquity, philosophers, theologians, and scientists have been interested in human memory; however, researchers today are still working to understand the capabilities, boundaries, and architecture. While the storage capabilities of long-term memory are seemingly unlimited (Bahrick, 1984), working memory, or the ability to maintain and manipulate information held in memory, seems to have stringent capacity limits (e.g., Cowan, 2001). Individual differences, however, do exist and these differences can often predict performance on a wide variety of tasks (cf. Engle, 2001). Recently, researchers have promoted the enticing possibility that simple behavioral training can expand the limits of working memory which indeed may also lead to improvements on other cognitive processes as well (cf. Morrison&Chein, 2011). The current study investigated this possibility. Recommendations from the skill training literature (cf. Schneider, 1985) were incorporated to create optimized verbal and spatial working memory training tasks. Significant performance improvements were evident across eight days of cognitive training using verbal and spatial adaptive n-back procedures. Training-related improvements were also evident for some untrained measures of visual short-term memory, attentional control, and working memory. These training effects, however, were not universal. Other measures of visual short-term memory and attentional control, as well as measures of fluid intelligence were unaffected by training.

The aim of this thesis was to investigate how visual information is organised in perceptual short term memory, with special interest in colour, spatial frequency and velocity. Previous studies of VSTM have indicated the existence of specific memory mechanisms for visual attributes such as orientation, spatial frequency, velocity, contrast and colour. The retention of information in visual short term memory for these basic visual attributes can be disrupted by the presentation of masking stimuli during inter-stimulus intervals (ISIs), which are outside the range of traditional sensory masking. We exploited this memory masking effect in order to examine the organisation of visual information in VSTM. Four groups of experiments were conducted in which participants carried out a delayed discrimination paradigm that employed a two-alternative forced choice (2-AFC) procedure in conjunction with a method of constant stimuli. The fidelity of VSTM was measured by performance markers such as discrimination thresholds and point of subjective equalities. We have found selective memory masking effects, which serve as further evidence in favour of the modular organisation in VSTM, namely, that human visual perceptual memory is based upon multiple, tuned channels in case of colour, spatial frequency and speed, similar to those found in the earliest stages of visual processing for spatial frequency. Moreover, each of these storage mechanisms are tuned to a relatively narrow range of stimulus parameters that are closely linked to visual discrimination mechanisms. These findings add further support to the view that low-level sensory processing mechanisms form the basis for the retention of colour, spatial frequency and velocity information in perceptual memory. We also found evidence for the broad range of transfer of memory masking effects across spatial location, which indicates more long range, long duration interactions between channels that are likely to rely upon contributions from neural processes located in higher visual areas. In conclusion, the experiments presented in this thesis provide significant insight into the organization of visual information in perceptual short term memory.

This study investigated the relationship between working memory and language in typically developing young children. The aim was to gain a better understanding of language development, in particular, the involvement of visual and verbal short-term memory in language acquisition and its influence on vocabulary size. It explored possible underlying causes of why some children have problems in the process of learning to talk, whereas other children acquire language easily. A total of 51 New Zealand English speaking children aged two to five completed a battery of assessments measuring receptive and expressive vocabulary and visual and verbal short-term memory. The standardized tests administered included the Receptive One Word Picture Vocabulary Test (Brownell, 2000b), the Expressive One Word Picture Vocabulary Test (Brownell, 2000a), the Visual Patterns Test (Stokes, Klee, Cruickshank, & Pleass, 2009), and the Test of Early Nonword Repetition (Stokes & Klee, 2009a). Receptive vocabulary knowledge was strongly associated with visual (r = .75) and verbal (r = .60) short-term memory performance and age (r = .72). The relationship of expressive vocabulary to visual short-term memory (r = .80) was stronger than to verbal short-term memory (r = .62) but significant for both and also for age (r= .83). Significant unique predictors for expressive vocabulary were age (R2 change = .60) as well as visual (R2 change = .04) and verbal (R2 change = .04) short-term memory. However, age appeared to be the only unique predictor for receptive vocabulary (R2 change = .54). In addition, the findings suggested that visual and verbal short-term memory increases as children get older. Hence, the Visual Patterns Test and Test of Early Nonword Repetition seem to be good predictors, over and above age, of expressive vocabulary knowledge.

Yes / Where do the bottlenecks for information and attention lie when our visual system processes incoming stimuli? The human visual system encodes the incoming stimulus and transfers its contents into three major memory systems with increasing time scales, viz., sensory (or iconic) memory, visual short-term memory (VSTM), and long-term memory (LTM). It is commonly believed that the major bottleneck of information processing resides in VSTM. In contrast to this view, we show major bottlenecks for motion processing prior to VSTM. In the first experiment, we examined bottlenecks at the stimulus encoding stage through a partial-report technique by delivering the cue immediately at the end of the stimulus presentation. In the second experiment, we varied the cue delay to investigate sensory memory and VSTM. Performance decayed exponentially as a function of cue delay and we used the time-constant of the exponential-decay to demarcate sensory memory from VSTM. We then decomposed performance in terms of quality and quantity measures to analyze bottlenecks along these dimensions. In terms of the quality of information, two thirds to three quarters of the motion-processing bottleneck occurs in stimulus encoding rather than memory stages. In terms of the quantity of information, the motion-processing bottleneck is distributed, with the stimulus-encoding stage accounting for one third of the bottleneck. The bottleneck for the stimulus-encoding stage is dominated by the selection compared to the filtering function of attention. We also found that the filtering function of attention is operating mainly at the sensory memory stage in a specific manner, i.e., influencing only quantity and sparing quality. These results provide a novel and more complete understanding of information processing and storage bottlenecks for motion processing. / Supported by R01 EY018165 and P30 EY007551 from the National Institutes of Health (NIH).

The aim of this thesis was to investigate how visual information is organised in perceptual short term memory, with special interest in colour, spatial frequency and velocity. Previous studies of VSTM have indicated the existence of specific memory mechanisms for visual attributes such as orientation, spatial frequency, velocity, contrast and colour. The retention of information in visual short term memory for these basic visual attributes can be disrupted by the presentation of masking stimuli during inter-stimulus intervals (ISIs), which are outside the range of traditional sensory masking. We exploited this memory masking effect in order to examine the organisation of visual information in VSTM. Four groups of experiments were conducted in which participants carried out a delayed discrimination paradigm that employed a two-alternative forced choice (2-AFC) procedure in conjunction with a method of constant stimuli. The fidelity of VSTM was measured by performance markers such as discrimination thresholds and point of subjective equalities. We have found selective memory masking effects, which serve as further evidence in favour of the modular organisation in VSTM, namely, that human visual perceptual memory is based upon multiple, tuned channels in case of colour, spatial frequency and speed, similar to those found in the earliest stages of visual processing for spatial frequency. Moreover, each of these storage mechanisms are tuned to a relatively narrow range of stimulus parameters that are closely linked to visual discrimination mechanisms. These findings add further support to the view that low-level sensory processing mechanisms form the basis for the retention of colour, spatial frequency and velocity information in perceptual memory. We also found evidence for the broad range of transfer of memory masking effects across spatial location, which indicates more long range, long duration interactions between channels that are likely to rely upon contributions from neural processes located in higher visual areas. In conclusion, the experiments presented in this thesis provide significant insight into the organization of visual information in perceptual short term memory. / Federation of Ophthalmic and Dispensing Opticians

The ability to hold visual information in mind over a brief delay is critical for acquiring information and navigating a complex visual world. Despite the ubiquitous nature of visual short-term memory (VSTM) in our everyday lives, this system is fundamentally limited in capacity. Therefore, the potential to improve VSTM through training is a growing area of research. An emerging body of literature suggests that extensive experience playing action video games yields a myriad of perceptual and attentional benefits. Several lines of converging work provide evidence that action video game play influences VSTM as well. The current study utilized a training paradigm to examine whether action video games cause improvements to the quantity and/or the quality of information stored in VSTM and whether these VSTM advantages extend visual working memory (VWM). The results suggest that VSTM capacity is increased after action video game training, as compared to training on a control game, and that some limited improvement to VSTM precision occurs with action game training as well. The VSTM improvements seen in individuals trained on an action video game are not better accounted for by differences in motivation or engagement, differential expectations, or baseline differences in demographics as compared to the control group used. However, these findings do not appear to extend to measures of VWM, nor to verbal working memory. In sum, action video game training represents a potentially unique and engaging platform by which this severely capacity-limited VSTM system might be enhanced. / Psychology