Lec (4): Distance/Size, Top down influences, Ecological approach

Introduction to Visual Ambiguities

  • Focus on distance and size ambiguities resolution.

  • Discuss influences on visual perception, particularly top-down processes.

  • Importance of external visual information in resolving ambiguities.

Distance and Size Cues

Conceptual Framework

  • Distance and size ambiguities are resolved through the combination of visual clues.

  • Types of visual cues:

    • Motor cues.

    • Cues from retinal imagery.

    • Additional observational clues.

Motor Cues

  • Eye Movement Cues:

    • The Okamoto Kiehl's Wear Vision System illustrates how eye muscle movement helps infer distance.

    • Accommodation:

      • Movement of the lens thickens to focus on nearby objects.

    • Convergence:

      • The inward movement of eyes (crossing) indicates close proximity of objects.

Retinal Imagery Cues

  • Different Perspectives:

    • Rapidly switching between eyes shows differing perspectives when objects are near (greater disparity).

    • Distant objects present less difference between left and right perspectives, helping gauge distance.

Additional Cues for Distance and Size

  • Familiar Size:

    • Past experiences help gauge the size of objects; for example, estimating the height of distant buildings.

  • Pictorial Cues:

    • Spatial orientation of lines aids in estimating depth.

    • Smaller angles signify greater distances.

  • Relative Height:

    • Objects appearing lower in an image are perceived as closer.

  • Linear Perspective:

    • Parallel lines converge at a vanishing point, indicating distance.

  • Atmospheric Cues:

    • Far-away objects may appear hazy or bluish, suggesting greater distance.

Top-Down Processing

Overview of Processing Methods

  • Bottom-Up Processing:

    • Sensory information is processed and recognized by the system in a linear flow.

  • Contextual Influence:

    • Prior knowledge influences how sensory information is interpreted (top-down processing).

Experiment by Steven Palmore (1975)

  • Participants view a kitchen scene with jagged objects.

  • Results: 80% correctly identify a loaf of bread, lower for the mailbox and drone due to contextual recognition.

  • Conclusion:

    • Context is crucial in visual processing, demonstrating the importance of both bottom-up and top-down processing.

Pawson Paradox

  • Example of letters A, B, and C as parts of Abraham Lincoln's face.

  • Recognition occurs better collectively than in isolation, illustrating simultaneous reliance on both processing types.

Ecological Approach to Visual Processing

Critique of Inferential Approach

  • Inferential approach emphasizes reliance on assumptions, considering retinal images as poor world representations.

  • Emphasizes the necessity for meaningful interpretations of visual stimuli.

Ecological Perspective

  • Touts environmental information availability reducing assumptions needed in interpretation.

Examples of Ecological Information Sources

  1. Object Size:

    • Estimation of tree size by contextually interpreting horizon lines (intersecting at the middle), even subconsciously.

    • The integration of ecological and inferential approaches enhances object size/distance determination.

  2. Motion and Optical Flow:

    • Moving towards a point alters relative points of light (vector flow field).

    • Visual perception allows relative motion interpretation (e.g., mountains appearing slower moving compared to fields).

Conclusion

  • Preview of upcoming video on face and familiar object recognition and processing differences.