Projects
Biological Motion Perception

Biological Motion Perception

Overview

How Visual Familiarity Modulates Biological Motion Processing
📅 Oct 2017 – Jan 2019
🏛️ University of Skövde, Sweden
👥 Collaborators: Karl Drejing, Paul Hemeren

This project investigated how visual familiarity and spatial orientation affect biological motion perception of walking actions. Through two controlled experiments using point-light displays (PLDs), we examined:

  • How incidental processing of flanker stimuli modulates attention
  • Kinematic differences between forward/backward walking
  • Processing hierarchies for upright vs. inverted biological motion

Stimuli & Apparatus

  • Forward & Backward Walkers: Point-light stimuli (13-dot male gait) captured via motion capture at Skaraborg Gait Laboratory.
  • Display: Visualized using MATLAB with Biomotion Toolbox-2 and Psychtoolbox-3, displaying white dots on a black background.

Experimental Design

Exp 1: Flanker Paradigm: Participants (N=20) identified walking direction of central target while ignoring flankers:

  • Target variables: Orientation (Upright/Inverted) & Walking style (Forward/Backward)
  • Flanker variables: Type (Unscrambled/Scrambled) & Congruency (Same/opposite direction as target)
  • Design: 2×2×2×2×2 factorial (3,280 trials)
  • Measures: Reaction time (RT) and accuracy

Exp 2: Isolated Target: Participants (N=9) identified walking direction of single targets:

  • Target Variables: Orientation × Walking style
  • Design: 2×2 factorial (320 trials)
  • Measures: Reaction time (RT) and accuracy

Key Findings

  1. Processing Hierarchies:

    • Upright forward-walking: Elicited the fastest response time (M=0.765s) and highest accuracy (99.6%), relying on global form processing (“vision-at-a-glance”).
    • Inverted backward-walking: Showed the slowest response time (M=1.386s) and lowest accuracy (92.5%), requiring local motion scrutiny (“vision-with-scrutiny”).

  2. Flanker Interference Effects:

    • Congruency effect: 39ms faster RT when flankers matched target direction
    • Strongest interference: Upright unscrambled flankers on inverted targets
    • Scrambled flankers: 213ms faster RT than unscrambled

  3. Kinematic Differences

    • Forward walkers: Larger vertical displacement, higher acceleration peaks
    • Backward walkers: Smoother deceleration, smaller stride span
    • Critical cue: Acceleration components in swing phase

Impact & Applications

  • Cognitive Science: Quantified visual familiarity effects in biological motion based on Reverse-Hierarchy visual-processing model.
  • Human-Robot Interaction: Inform attention models for social robots and guide animation design for natural movement perception.
  • XR Systems: Provides principles for intuitive virtual agent locomotion and optimization strategies for biological motion rendering.

Project Outcomes

📚 See Dataset Publication

Collaboration Opportunities

Open to collaboration or discussion on methodology, data, or future directions. Happy to exchange ideas and explore new perspectives.