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Medium versus difficult visual search: How a quantitative change in the functional visual field leads to a qualitative difference in performance

Hulleman, Johan; Lund, Kristofer; Skarratt, Paul A.


Johan Hulleman

Kristofer Lund


The dominant theories of visual search assume that search is a process involving comparisons of individual items against a target description that is based on the properties of the target in isolation. Here, we present four experiments that demonstrate that this holds true only in difficult search. In medium search it seems that the relation between the target and neighbouring items is also part of the target description.
We used two sets of oriented lines to construct the search items. The cardinal set contained horizontal and vertical lines, the diagonal set contained left diagonal and right diagonal lines. In all experiments, participants knew the identity of the target and the line set used to construct it. In difficult search this knowledge allowed performance to improve in displays where only half of the search items came from the same line set as the target (50% eligibility), relative to displays where all items did (100% eligibility). However, in medium search, performance was actually poorer for 50% eligibility, especially on target-absent trials.
This opposite effect of ineligible items in medium search and difficult search is hard to reconcile with theories based on individual items. It is more in line with theories that conceive search as a sequence of fixations where the number of items processed during a fixation depends on the difficulty of the search task: When search is medium, multiple items are processed per fixation. But when search is difficult only a single item is processed.


Hulleman, J., Lund, K., & Skarratt, P. A. (2020). Medium versus difficult visual search: How a quantitative change in the functional visual field leads to a qualitative difference in performance. Attention, Perception, and Psychophysics, 82(1), 118-139.

Journal Article Type Article
Acceptance Date May 28, 2019
Online Publication Date Jul 2, 2019
Publication Date 2020
Deposit Date Aug 14, 2019
Publicly Available Date Sep 5, 2019
Journal Attention, Perception, and Psychophysics
Print ISSN 1943-3921
Electronic ISSN 1943-393X
Publisher Springer Verlag
Peer Reviewed Peer Reviewed
Volume 82
Issue 1
Pages 118-139
Public URL
Publisher URL


Article (832 Kb)

Copyright Statement
© The Author(s) 2019
Open Access
This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

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