Review on The 
Comparison of Visual Working Memory Representations with Perceptual Inputs Joo-seok Hyun 1 , Geoffrey F. Woodman 2 , Edward K. Vogel 3 , Andrew Hollingworth 4 and Steven J. Luck 5 1 Chung-Ang University, 2 Vanderbilt University, 3 University of Oregon, 4 University of Iowa and 5 University of California, Davis INTRODUCTION This article presents a critical review of the paper 'The Comparison of Visual Working Memory Representations with Perceptual Inputs'. It is an account of the rationale behind the work, the methodologies adopted, the outcomes and the conclusions of the work. RATIONALE Visual cognition is not been fully speculated. In order to have an in-depth understanding of the Visual Cognitive system, aspects like visual perception, storage of data in Visual Working Memory (VWM), eye movement, visual recognition and attention have to be comprehended well. Prior research in this field had largely neglected the processes involved during comparison of data stored in VWM with the current visual input. This paper focuses on finding out the nature of this comparison process and the mental processing steps involved in doing so. It does so by drawing an analogy between the above mentioned comparison process and a visual search task. METHODS AND RESULTS The work involves 5 experiments which sequentially tackle the problem at hand. Hyun et al. hypothesized the ease of detecting the existence of a modification in the sample and test inputs as compared to detecting the nonexistence of the modification. Experiment 1 relates the current problem of visual comparison to the prior work on visual search and change detection. The participants were sequentially shown a sample input and a test input (after a delay) and were asked to respond (by the pressing of either of the 2 buttons) depending on whether a change (Exp 1a) or sameness (Exp 1b) was observed or not. The response time and error rate versus set size (of visual input) graphs (click here to view) conformed to the results of the previous studies on visual search as well as change detection. This led to the question of whether this change/sameness detection was a limited or an unlimited capacity process. Hyun et al. hypothesized that the comparison consists of a two-step process- the first being an unlimited capacity process that results in the shift of attention indicating the detection of change/sameness and the second being a limited capacity verification process as the first step does not bring the relevant information, required to produce the response, into focus and hence the second step is a must. To test this hypothesis, Experiment 2 and 3 were carried out wherein the set size was varied and the covert and overt attention prior to the physical button pressing response was measured via N2pc latency and eye position respectively. The results (statistical data: Exp2, Exp3) showed minimal variation with set size, hence are consistent with the first step of the hypothesis. Experiment 4 was then conducted that measured the response time of button pressing. The results of this experiment (click here to view) clearly indicate the set size dependence of the response time arising from the second limited capacity step of the comparison process. Finally, to test whether the visual comparison process, just like the visual search task, involves a voluntary attention diversion based on the task at hand and some slight involuntary attention as a result of changes in irrelevant input as well. Experiment 5 measured response time by varying pertinent as well as irrelevant elements of the input data independently. The results of this experiment (click here to view) conformed to the above hypothesis of voluntary control. CONCLUSION The study outlines the following aspects of the mental processing during comparison between the information stored in Visual Working Memory and the sensory input. The change/ sameness detection process can be regarded as special instance of the visual search task. Detecting a change among similar elements is much easier as compared to detecting sameness among different elements. The comparison process involves an initial unlimited capacity process involving shift in attention to the element to be considered and a limited capacity verification process before the response is made. The distribution of attention to the change is a voluntary process. However, an irrelevant change also might take some share of our attention process leading to delay in the response. FUTURE WORK A major issue that was left out in the experimental studies done in this work is, why our cognitive system carries out the initial unlimited capacity processing when ultimately, the response will be produced only after the limited capacity processing. A plausible explanation for this could be the importance of the initial unlimited capacity processing in some low-level visual processing. Studies have to be yet conducted in order to speculate the above. Also, various other aspects of visual cognition are yet to be unraveled. Click here to view statistical results of the study
