Academic journal article Attention, Perception and Psychophysics

Top-Down Expectancy versus Bottom-Up Guidance in Search for Known Color-Form Conjunctions

Academic journal article Attention, Perception and Psychophysics

Top-Down Expectancy versus Bottom-Up Guidance in Search for Known Color-Form Conjunctions

Article excerpt

Published online: 22 July 2015

# The Psychonomic Society, Inc. 2015

Abstract We assessed the effects of pairing a target object with its familiar color on eye movements in visual search, under conditions where the familiar color could or could not be predicted. In Experiment 1 participants searched for a yellow- or purple-colored corn target amongst aubergine distractors, half of which were yellow and half purple. Search was more efficient when the color of the target was familiar and early eye movements more likely to be directed to targets carrying a familiar color than an unfamiliar color. Experiment 2 introduced cues which predicted the target color at 80 % validity. Cue validity did not affect whether early fixations were to the target. Invalid cues, however, disrupted search efficiency for targets in an unfamiliar color whilst there was little cost to search efficiency for targets in their familiar color. These results generalized across items with different colors (Experiment 3). The data are consistent with early processes in selection being automatically modulated in a bottom-up manner to targets in their familiar color, even when expectancies are set for other colors.

Keywords Visual search . Eye movements and visual attention . Visual perception

Introduction

There is a large body of research on visual search indicating that search efficiency is determined by visual differences between targets and distractors and also between the distractors themselves (e.g., Duncan & Humphreys, 1989; Wolfe, 2003). There has been much less work into how search is modulated by the stored knowledge the observer can call upon to direct search. Nevertheless, there is evidence that stored knowledge mediates search efficiency, reflected in effects of stimulus familiarity on performance. For example, search for a 2 target amongst 5 distractors is easier than when the items are rotated by 90° (Wang, Cavanagh, & Green, 1994), indicating that the familiarity of the distractors facilitates how easily they can be rejected in a search. Similarly, search for a target can be facilitated if participants hear the sounds the target makes during the search process (Iordanescu, Grabowecky, Franconeri, Theeuwes, & Suzuki, 2010). In addition, search for a target is influenced by the presence of semantically related distractors, even when the target is absent from the display (Belke, Humphreys, Watson, Meyer, & Telling, 2008; Moores, Laiti, & Chelazzi, 2003; Telling, Kumar, Meyer, & Humphreys, 2009) - consistent with stored representations for items related to an expected target affecting the search process. Recent work has also shown that presenting an object in its familiar color can also moderate a search, even when color is irrelevant for the task (Rappaport, Riddoch, & Humphreys, 2013, see also Wildegger, Riddoch, & Humphreys, 2015). The present paper focuses on this latter result, using eye movements to assess the microgenesis of a search within a trial. We ask whether presenting an object in its familiar color modulates the early eye movements on a trial, consistent with the familiar combination of the colored shape affecting early selection processes. In addition, we evaluate whether the familiarly colored target shape can direct the early stages of search even when that item is not expected. Furthermore, we investigate whether introducing expectations about the target alters the effect of target-familiarity on the progression of search.

Questions about how search proceeds for colored shapes are theoretically important as major theories of visual attention, such as Feature Integration Theory (Treisman, 1998), hold that a critical constraint on search is whether targets are distinguished by the presence of a single feature difference relative to distractors, or whether items differ in the conjunction of features (e.g., color and form). Search for targets defined by a conjunction of features is often inefficient, consistent with participants needing to attend to each item in order to bind their features (e. …

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