Visual assessment of causality in the Poisson effect

Area of Science:

• Psychology
• Physics
• Perception Science

Background:

• The Poisson effect describes the causal relationship between stretching a material along one axis and its compression along the orthogonal axis.
• Understanding how humans perceive this physical phenomenon is crucial for fields ranging from material science to human-computer interaction.

Purpose of the Study:

• To investigate the perceptual cues and heuristics human observers utilize when assessing causality in the Poisson effect.
• To determine if physical properties, such as Poisson's ratio, influence the perceived causality of material deformation.

Main Methods:

• Participants viewed video stimuli of a rectangular region undergoing horizontal stretching and vertical compression.
• The magnitude of vertical compression was modulated sinusoidally.
• Observers reported their perception of causality for the observed deformations.

Main Results:

• The physical index of the Poisson effect, Poisson's ratio, did not correlate with the degree of reported causality.
• Perceived causality was significantly explained by image features related to the magnitude of deformation.
• Causality assessment did not consistently require comparing the material's shape before and after deformation.

Conclusions:

• Human observers do not rely on the physical definition of Poisson's ratio to assess causality in material deformation.
• Perceptual heuristics based on readily available image features, particularly deformation magnitudes, guide the assessment of Poisson effect causality.
• This suggests a dissociation between the physical properties of a material and human perceptual judgments of its behavior.