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Methods to Explore the Influence of Top-down Visual Processes on Motor Behavior
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Opposite size illusions for inverted faces and letters.

Eamonn Walsh1, Carolina Moreira2, Matthew R Longo2

  • 1Department of Basic & Clinical Neuroscience, Institute of Psychiatry, Psychology & Neuroscience, King's College London, UK; Cultural and Social Neuroscience Research Group, Institute of Psychiatry, Psychology & Neuroscience, King's College London, UK.

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Visual illusions reveal how the brain processes faces and words. Faces show a size illusion, while letters and words exhibit a reverse effect, indicating early perceptual processing.

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Area of Science:

  • Cognitive psychology
  • Neuroscience
  • Visual perception

Background:

  • Faces and words are crucial for communication, processed by specialized brain regions.
  • A known size illusion makes inverted faces appear larger than upright ones.
  • This study explores if similar illusions apply to letter and word perception.

Purpose of the Study:

  • To investigate the presence of a size illusion for individual letters, words, and pseudowords.
  • To compare the size illusion effects between faces, letters, and words.
  • To understand the perceptual stages involved in these visual illusions.

Main Methods:

  • Replication of the face size illusion with upright and inverted stimuli.
  • Experiment 1: Testing the size illusion with individual letters.
  • Experiment 2: Testing the size illusion with visual words and pseudowords.

Main Results:

  • A robust size illusion was confirmed for faces.
  • Letters, words, and pseudowords demonstrated a reverse size illusion.
  • Unfamiliar letters also exhibited a reverse size illusion, similar to human bodies.

Conclusions:

  • The size illusion occurs in early perceptual stages, before semantic processing.
  • A general mechanism for encoding curvilinear shapes may underlie these illusions.
  • Contrasting size illusion effects for faces and words suggest specialized, independent processing and distinct neural encoding.