The capacity of multiple-target search

Abstract

Can individuals look for multiple objects at the same time? A simple question, but answering it has proven difficult. In this review, we describe possible cognitive architectures and their predictions about the capacity of visual search. We broadly distinguish three stages at which limitations may occur: (1) preparation (establishing and maintaining a mental representation of a search target), ( 2) selection (using this mental representation to extract candidate targets from the visual input), and (3) post-selection processing (verifying that the selected information actually is a target). We then review the empirical evidence from various paradigms, together with their strengths and pitfalls. The emerging picture is that multiple target search comes with costs, but the magnitude of this cost differs depending on the processing stage. Selection appears strongly limited, while preparation of multiple search target representations in anticipation of a search is possible with relatively small costs. Finally, there is currently not sufficient information to determine the capacity limitations of post-selection processing. We hope that our review contributes to better targeted research into the mechanisms of multiple-target search. A better understanding of multiple-target search will also contribute to better design of real-life multiple-target search problems, reducing the risk of detrimental search failures.

Memory for stimulus duration is not bound to spatial information

“…Another, subtly different account would pose that perception-and comparison of duration make use of different representations of the Interval 1 duration, and that transforming one into the other is an active process. Such transformations of have been proposed to be used for visual search (Myers et al, 2017), where multiple items can be perceived and stored in working memory, after which only one relevant item is actively transformed into a 'template' that guides attentional selection without interference from others (see also Chatham et al, 2014;Olivers et al, 2011;Ort & Olivers, 2020). However, one key difference is that for visual search there is strong evidence that transformed representations still make use of the spatial code (de Vries et al, 2018;de Vries et al, 2017de Vries et al, , 2019, whereas for temporal information this association appears to be absent.…”

EEG Cross-Frequency Phase Synchronization as an Index of Memory Matching in Visual Search

“…We cannot rule out these possibilities. Alternatively assuming a parallel mode, would predict that multiple templates interacted in parallel with sensory input; however, this would come at costs due to mutual competition, leading to a delay in target selection (Ort et al, 2019; Ort & Olivers, 2020). For the matching phase, this may mean that when one out of multiple targets must be found, the matching process would happen later than for a single possible target, but consistently, with low temporal variability across trials.…”

“…Bays & Husain, 2008). In a range of different paradigms, clear multiple target costs have been found both on the behavioral and the EEG level, indicating that multiple-target search seems to be limited in capacity, however, evaluating the exact processing stage at which serial or parallel processing limitations occur, has proven difficult or led to sometimes mixed results (for review, see Ort & Olivers, 2020). The aim of the current study was to investigate the stage of memory matching, by measuring theta-gamma phase synchronization as a proposed neural correlate.…”

“…As mentioned earlier, alternatives to these serial models exist, but while parallel processing during selection and preparation may be possible, it is yet also relatively unclear whether this could generalize from paradigms with relatively simple target features (e.g. color) to paradigms utilizing more complex target stimuli (Ort & Olivers, 2020). But in any case, a single mental template should enable a fast and precise memory matching, whereas a larger number of mental templates that could potentially be matched to visual input should come at costs that disable such an early and precise matching process.…”

The Predation Game: Does dividing attention affect patterns of human foraging?

“…Extending the classic singletarget paradigm, a number of groups have also examined search behaviour in tasks where multiple targets must be located on a given trial (e.g., Cain et al, 2012;Fougnie et al, 2015;Gilchrist et al, 2001;Hills et al, 2012Hills et al, , 2013Á. Kristjánsson et al, 2014Ort & Olivers, 2020;Pellicano et al, 2011;Thornton & Horowitz, 2004Wolfe et al, 2016Wolfe et al, , 2019.…”