Visual working memory load does not affect the overall stimulus processing time in visual search

Abstract

The dual-task paradigm is widely used in studying the interaction between visual search and working memory. A number of studies showed that holding items in working memory delays the overall response time (RT) in visual search, but it does not affect the efficiency of search (i.e., the slope of the RT × set size function). Why the memory load merely affects the overall RT? Some researchers proposed that this load-effect on overall RT may be caused by factors that only affect response selection processes, while others argued that it may reflect the effect of visual working memory load on visual search. This study investigated the two competing hypotheses by measuring the threshold stimulus exposure duration (TSED) for successfully fulfilling a search task. Experiment 1 replicated the large overall RT difference with the RT method but only found a small though reliable overall TSED difference with the TSED method. Experiment 2, with better controls, found no TSED difference by manipulating the visual working memory load. Experiment 3 showed that the TSED is not influenced by processes in the response selection stage. The present findings suggest that the overall stimulus processing time in visual search is not affected by visual working memory load and that the effect of memory load on overall RT is largely due to factors affecting response selection alone.

Dual-task costs in memory recall precision reflect shared representational space.

“…A dual-task paradigm is often used to examine the interaction between two distinct mental mechanisms, such as the interaction between attention and WM (e.g., Woodman et al, 2001; Xin & Li, 2020), and the interaction between spatial WM and visual WM (e.g., Sanada et al, 2015; Wood, 2011). However, because attention is involved in the maintenance of WM (Barrouillet et al, 2011; Cowan, 2005), when dual-task cost in capacity is observed in a WM task it is often difficult to tell whether the dual-task cost is due to interference from executive processes or from nonexecutive processes (such as interference across WM representations).…”

Do Different Types of Spatial Working Memory Load Affect Visual Search Differently?

“…Hence, additional experiments in which the eye movements are monitored during search are necessary to further investigate these diverging effects of WM load on search performance and search efficiency. A further explanation for this inconsistency regarding the different effect of spatial WM load on search performance and search efficiency was recently provided by Xin and Li (2020). They argued that the increased extent of executive control to maintain a (non-spatial) WM load might decrease the participants' confidence level such that the observed response time differences are mainly due to the stage of response selection.…”