Evaluating comparative and equality judgments in contrast perception: attention alters appearance

Area of Science:

• Visual perception
• Cognitive neuroscience
• Psychophysics

Background:

• Covert attention influences visual task performance and feature appearance.
• Previous studies used comparative judgments to assess attention's effect on appearance.
• A recent equality task study questioned these findings, proposing decision bias in comparative judgments.

Purpose of the Study:

• To compare biases and sensitivity to perceived contrast shifts between comparative and equality judgment paradigms.
• To empirically test the validity of the equality judgment procedure for assessing attention's effect on visual appearance.
• To investigate methodological limitations of the equality paradigm.

Main Methods:

• Contrast appearance was measured using both comparative and equality judgment tasks.
• Participants judged contrasts of simultaneously presented stimuli.
• Stimuli contrasts were physically incremented or exogenous attention was directed to one stimulus.

Main Results:

• Methodological limitations were identified in the equality judgment paradigm.
• Both paradigms successfully captured perceptual shifts due to physical and perceived contrast changes.
• Attention was shown to enhance apparent contrast, regardless of the judgment method.

Conclusions:

• The equality paradigm has limitations for assessing visual perception.
• Both comparative and equality judgments can detect changes in perceived contrast.
• Covert attention demonstrably enhances apparent contrast, validating previous findings.