21 August 2015

Working Memory Load and Distraction: Dissociable Effects of Visual Maintenance and Cognitive Control – An Article Review

*Italics are directly quoted from the article.

For this review, I chose an article entitled, Working memory load and distraction: dissociable effects of visual maintenance and cognitive control authored by Nikos Konstantinou, Eleanor Beal, Jean-Remi King and Nilli Lavie. The article was published on the Journal of Attention, Perception and Psychophysics (2014) and was available online on 2 August 2014 at Springerlink. After browsing through some of the contents, I chose the article entitled above because it is related to my current field of interest, cognitive science – which is also considered to be a vital discipline associated with psychology especially in terms of assessment and research.

The study focused not on a single topic, rather on a combination of interrelated factors which it simultaneously explored while drawing insights from previously conducted studies and experiments. Based from the earlier researches and backgrounds on both cognitive psychology and experimental neuroscience, it formulated a number of hypotheses and a series of experiments, the results of which ‘confirmed load theory predictions that provided a novel functional distinction between the roles of working maintenance and cognitive control in selective attention.’ It ‘enhanced the understanding of how working memory and selective attention interact. Working memory load can be either detrimental or beneficial to focused attention, depending on whether maintenance or cognitive control functions are loaded.
In order to understand the back-drop upon where the study is based, I quote from the introduction which I take to be its main premise,
The extent to which selective focused attention allows people to successfully ignore irrelevant distractions is central to our understanding of attention and cognitive control.
It is now well established that the ability to ignore irrelevant distractions is not determined just by the intention to be focused or by the separability of the target and distractor stimuli, but also by the level and type of processing load involved in the current task.
Working Memory (WM) is the main theme of the study. It is a complex system of two functions, namely: [a] Executive cognitive control and [b] Visual maintenance. Executive cognitive control functions are typically revealed in tasks related to verbal working memory, while Visual maintenance functions are exhibited through visual and spatial working memory tasks. It is these two functions of Working Memory (WM) that the study aimed to investigate: how can they be dissociated (differentiated, separated) through the opposite effects of load on selective attention?

Hence, it is through this dissociation (differentiation, separation) of the two functions of Working Memory (WM) that a distinct variable had to be manipulated: load on selective attention. The study therefore takes on an Experimental Approach in order to test its presumed hypotheses stated on the introduction and on the beginning of each experiment— and in order to achieve this, had to First: operationally define the two functions of Working Memory (WM) and in what activity can they be exhibited and measured; and Second: in what manner can load on selective attention be performed on each Working Memory (WM) function, and what specific tasks are to be undertaken (or how the load can be manipulated) in order to find the dissociable effects of load and eventually, distraction.

How Working Memory (WM) had been divided into two functions and how the presumed variable would have effect or effects of dissociating or differentiating the two was based on a theory proposed in Lavie’s load theory which ‘applied a capacity approach to selective attention, while taking into account the role of priority-based Working Memory (WM) control. Load on Working Memory (WM) cognitive control functions also plays an important role. Conditions of high Working Memory (WM) load that reduce its availability to exert priority-based control over the task result in increased processing of irrelevant distractors (due to the reduced distinction between relevant and irrelevant information). Thus, Working Memory (WM) load has the opposite effect on distractor processing to that of perceptual load (e.g., Lavie, 2005; Lavie et al., 2004).’

The experiments on the study were divided into two sets, each set containing two separate experiments. Experiment 1 was divided into 1a and 1b, while Experiment 2 was divided into 2a and 2b— all of which were conducted in a controlled manner.

Experiment 1 was intended to measure the effects of a manipulated load to Visual short-term memory (VSTM) - a Working Memory (WM) function on visual maintenance. For this experiment, the hypothesis of the study was ‘that loading sensory visual representation capacity by manipulating either VSTM maintenance or encoding would lead to reduced distractor.’ Experiment 2 on the other hand, measured the effects of manipulated load on the tasks exhibited by the executive cognitive control-Working Memory (WM) function. The hypothesis for the 2nd set of experiments was also the same as in experiments 1, ‘that increased VSTM load through higher set size would increase demands on visual representation capacity, and thus, lead to reduced distractor processing.

The study is a dynamic exploration of seemingly abstract concepts: working memory, executive cognitive control, visual maintenance, load, distraction. But it was able to quantify and measure and find relationships between the concepts not merely in linguistic terms but on an experimental level which I think is a breakthrough extending to the continuum of the previous studies upon which it was based.

It not only confirmed previous findings (provide a new line of support for the dissociation between Working Memory [WM] functions of storage and cognitive control e.g., Baddeley, 1996; Repovs & Baddeley, 2006; Smith & Jonides, 1999) but extended them, specifically the load theory – to accommodate the effects of different types of Working Memory (WM) load on selective attention.

Based from the results, two conclusions were generated: [1] Loading visual maintenance or encoding by increased set size for a memory sample of shapes, colors, and locations lead to reduced distractor response competition effects; and [2] loading working memory cognitive control with verbal rehearsal of a random letter set led to increased distractor effects.

Aside from sometimes confusing technical terms, I would suggest that the authors to have specifically defined the variables of the study. There is a removal of terms for example, ‘executive cognitive control’ becomes ‘cognitive control.’ There is a tendency for the reader to mistake both terms as corresponding to entirely different concepts. Terms such as ‘distraction,’ ‘load,’ ‘maintenance,’ ‘distractor congruency,’ etc. were all included in the experiments and data analysis and discussion but they were not exactly defined or on what specific context from the previous and present study they are to be understood or how they are made manifest in the experimental activity. Critique aside, the study is a breakthrough.

It is further recommended for future studies like this to utilize brain imaging results that would simultaneously be conducted with the participants during the experiment proper, and the results analyzed and correlated synchronously.