Perky Effect

What is the Perky Effect?

The Perky effect refers to interference from mental imagery with detecting or discriminating an external visual signal. The name derives from Cheves Perky’s 1910 imagery experiment.

Perky’s original setup

In Perky’s 1910 study, participants looked at a fixation point and imagined a colored object, such as a tomato or banana. Without being told, they also saw a faint colored form projected from behind the screen. Participants whose trials were not disrupted by apparatus errors reported the experience as imagination, although features of the projection entered their descriptions. For example, the banana appeared upright when some had expected to imagine it horizontally. This raises a question about source: was the experience attributed to imagination even though an external signal contributed to it?

Perky effect experiments

Segal and Gordon’s 1969 experiments distinguished confusing an image with a faint stimulus from reduced perceptual sensitivity during imagery. Their signal-detection results supported reduced sensitivity, rather than just a change in reporting preference.

What affects the Perky effect?

Imagery can also help perception. Reeves’s 2026 review and experiment describes facilitation at low and interference at high performance levels; vividness alone did not determine the change between them.

Thus, more vivid or more similar imagery does not invariably produce more interference. Stimulus strength and task conditions matter.

Why it matters

The experiments help separate two questions: did a person confuse imagination with something on the screen, or did imagining make the visual signal harder to detect? The effect concerns laboratory interactions between imagery and perception.

Boundary extension describes remembering a scene as extending beyond the area that was actually shown.