Visual Search Task

Each round shows a grid of colored shapes. In the feature condition you look for a red triangle among green triangles; in the conjunction condition you look for a red circle among red squares and green circles. Press the space bar (or click the display) as soon as you find the target; if there is none, simply wait. The experiment compares reaction times across set sizes 8, 16, and 24 in both conditions.

For each condition and set size, the average reaction time of correct target-present trials is computed, and a straight line (least-squares slope in ms per item) is fitted to those averages. Responses faster than 150 ms and incorrect trials are excluded from the reaction-time averages; target-absent accuracy is reported separately.

The slope of reaction time against set size is the key measure. A near-zero slope in the feature condition indicates parallel, pop-out search; a clearly positive slope in the conjunction condition indicates serial attentional checking of items, following the logic of feature-integration theory.

When a target differs in a single feature such as color or shape, it is found equally fast at any set size, because early vision detects elementary features everywhere at once. That is why the red triangle among green triangles feels effortless.

Clutter, low contrast between target and distractors, and feature conjunctions — the same factors that make radiology, security screening, and icon search demanding.

No. It is an educational, web-based adaptation: the stimuli are simplified geometric shapes, set sizes are reduced to 8, 16, and 24, and the session is shortened. It is suitable for self-exploration and demonstration, not for research-grade or clinical measurement.