Determinants of filled/empty optical illusion: differential effects of patterning

Area of Science:

• Visual Perception
• Psychophysics
• Spatial Cognition

Background:

• The Oppel-Kundt phenomenon describes the illusory overestimation of a path's length when subdivided.
• Previous explanations focused on space 'filling-up' or segment number.

Purpose of the Study:

• To investigate whether the form of visual dividers, not just their quantity or coverage, influences the illusory expansion of path length.
• To differentiate between space-filling and pattern-dependent factors in the Oppel-Kundt phenomenon.

Main Methods:

• Presented visual stimuli with subdivided paths, varying the spatial distribution and form of dividers.
• Kept the relative coverage of the filled space constant across conditions.
• Analyzed the magnitude of the illusory length overestimation.

Main Results:

• The magnitude of illusory space expansion significantly depended on the number of filling elements.
• The form of the visual dividers also significantly influenced the perceived length.
• These factors were more critical than simple space coverage.

Conclusions:

• Illusory space expansion is not solely due to 'filling-up' a space but is critically dependent on the visual pattern of subdivision.
• The findings refine theories of the Oppel-Kundt phenomenon, highlighting the role of specific visual cues.