2016-05-26 14:20:35

Changes in early optic flow experiences across development and culture

Swapnaa Jayaraman, Indiana University

Rick O. Gilmore, Penn State

Florian Raudies, HP Research

Supported by NSF BCE-1147440, NSF BCS-1238599, NICHD U01-HD-076595

Background

  • What is optic flow?
  • How does sensitivity to optic flow develop?
  • How do infants' natural experiences with optic flow develop?
  • Do the statistics of infants' natural experiences align with changes in sensitivity?

What is Optic Flow?

Optic Flow Components

How Does Optic Flow Sensitivity Develop?

Developmental Changes in Experiences of Optic Flow

Developmental/Cultural Factors

  • Posture: Walking vs. Crawling
    • Distance to ground surface
    • Head pitch relative to ground
  • Geometry: Typical distance to surfaces, objects; number of people, objects
  • Moving through space: self vs. object motion

Approach

  • Simulating changes in optic flow due to changes in body size & posture, geometry
  • Measuring flow experienced in natural contexts by head-mounted cameras

Optic Flow Equation

\(\begin{pmatrix}\dot{x} \\ \dot{y}\end{pmatrix}=\frac{1}{z} \begin{pmatrix}-f & 0 & x\\ 0 & -f & y \end{pmatrix} \begin{pmatrix}{v_x{}}\\ {v_y{}} \\{v_z{}}\end{pmatrix}+ \frac{1}{f} \begin{pmatrix} xy & -(f^2+x^2) & fy\\ f^2+y^2 & -xy & -fy \end{pmatrix} \begin{pmatrix} \omega_{x}\\ \omega_{y}\\ \omega_{z} \end{pmatrix}\)

Parameters For Simulation

Parameters for Simulation

Geometric Feature Distance
Side wall +/- 2 m
Side wall height 2.5 m
Distance of ground plane 32 m
Field of view width 60 deg
Field of view height 45 deg

Simulating Flow Fields

Flow Direction Distributions by Geometry & Posture

Simulated Flow Speeds (m/s)

Measuring Optic Flow in Natural Contexts

Sample characteristics

Country Females Males Age (wks) Coded video Hrs
India 17 13 3-63 3.1 (0.5-6.0)
U.S. 15 19 4-62 4.6 (0.2-7.6)



Data & excerpts: http://databrary.org/volume/81

Workflow

  • Extract optic flow from video, (code repo)
  • Human coders: is infant moving or stationary?
  • How do flow speeds and patterns vary by
    • Age
    • Geography/Culture
    • Moving/stationary status

Moving vs. Stationary Bouts