Visual Search

Background

Anne Treisman's Feature Integration Theory (Treisman & Gelade, 1980) proposed two modes of visual search:

Feature search (pop-out): When a target differs from distractors in a single basic feature (e.g., color), it is detected rapidly and in parallel regardless of set size.

Conjunction search: When the target shares features with different distractors (e.g., red vertical among red horizontal and green vertical), search requires serial inspection and RT increases linearly with set size.

The Set-Size Effect

The search slope (ms per additional item) is the hallmark measure. Feature search slopes are typically near 0–5 ms/item, while conjunction search slopes are 20–40 ms/item for target-present trials.

References

Treisman, A.M. & Gelade, G. (1980). A feature-integration theory of attention. Cognitive Psychology, 12, 97–136.

Wolfe, J.M. (1994). Guided Search 2.0: A revised model of visual search. Psychonomic Bulletin & Review, 1, 202–238.

Wolfe, J.M. (1998). Visual search. In H. Pashler (Ed.), Attention. Psychology Press.

On each trial, you'll see an array of colored bars. Your task is to determine whether a red vertical bar (the target) is present.

Press F if the target is present, or J if it is absent.

Two search types alternate in blocks:

Feature search: Target is unique in color (red among green) — should be easy!
Conjunction search: Target shares color OR orientation with distractors — harder.

Set sizes vary (4, 8, 16, 32 items). There are 80 trials total. Respond as quickly and accurately as possible.

Visual Search

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