Does grasping capacity influence object size estimates? It depends on the context.

Area of Science:

• Cognitive Psychology
• Perception Science
• Human Motor Control

Background:

• The action-specific account posits that perceived object size is modulated by motor intentions.
• Prior research indicated right-handers estimate objects as smaller when intending to grasp with their right hand, attributed to perceived grasping capacity.
• Replication failures suggest alternative explanations for this observed scaling effect.

Purpose of the Study:

• To investigate the role of demand characteristics in the right-hand bias of object size estimation.
• To differentiate between hypothesis guessing and contextual influences as sources of demand characteristics.
• To re-evaluate the validity of the action-specific account in explaining handedness-based size perception.

Main Methods:

• Three experiments were conducted to examine demand characteristics.
• Experiment 1 and 2 manipulated explicit instructions to test hypothesis guessing.
• Experiment 3 altered the experimental context to assess subtle influences on size estimation.

Main Results:

• No object size scaling effects were observed when participants received neutral instructions.
• Scaling effects emerged with explicit instructions mirroring the action-specific account's predictions.
• Contextual manipulation, mirroring previous studies, also elicited scaling effects.

Conclusions:

• Demand characteristics, particularly contextual influences, can account for previously reported object size scaling effects in right-handers.
• Hypothesis guessing does not appear to be the primary driver of these effects.
• The findings challenge the action-specific account's explanation based on perceived grasping capacity, suggesting methodological artifacts instead.