Boundary extension: Insights from signal detection theory

Area of Science:

• Cognitive Psychology
• Visual Perception
• Memory Studies

Background:

• Boundary extension is a common visual memory error where people recall seeing more than was originally visible.
• Previous research has not extensively applied signal detection theory (SDT) to understand this phenomenon.

Purpose of the Study:

• To investigate boundary extension using signal detection theory (SDT).
• To determine the contributions of discrimination sensitivity and response bias to boundary extension.

Main Methods:

• Two experiments were conducted where participants studied images presented in close-up or wide-angle views.
• Participants rated the similarity of test images (identical or altered angle) to the studied images on a 6-point scale.

Main Results:

• Both discrimination sensitivity and response bias were found to contribute to the boundary extension effect.
• A significant difference in discrimination sensitivity (at least 28%) was observed, refuting explanations based solely on response bias.
• Findings suggest participants experience false memories extending beyond the original visual field.

Conclusions:

• Boundary extension is not solely a result of response bias but involves genuine differences in perceptual discrimination.
• The results support the interpretation of boundary extension as a form of false memory, where individuals perceive a wider scene than was actually presented.