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

Distance and Size Ambiguities

  • Distance and size work in tandem to resolve visual ambiguities.

  • Visual perception combines clues to ascertain object size and distance.

    • Types of cues:

      • Motor cues

      • Cues from retinal imagery

      • Additional cues

Motor Cues

  • Okamoto Kiehl's Wear Vision System:

    • Utilizes eye muscle movement to determine object distance.

    • Accommodation:

      • When approaching an object, the lens thickens to focus better, signaling proximity.

    • Convergence:

      • Eyes move inward when focusing on close objects, providing distance information.

Retinal Imagery Cues

  • Changes in perspective with eye movement help gauge distance:

    • Example: Rapidly alternating eye closure on a nearby object reveals a larger positional difference than on distant objects.

Additional Cues

  • Familiar Size:

    • Use of experience to estimate object size.

    • Example: Recognizing a distant building is smaller than it appears, but estimating it as building-sized.

  • Pictorial Cues:

    • Size and Orientation of Lines:

      • Smaller angles indicate distance; larger angles suggest closeness.

    • Relative Height:

      • Objects lower in the picture plane are assumed closer than those higher up.

  • Linear Perspective:

    • Parallel lines converge towards a point, indicating distance.

  • Atmospheric Cues:

    • Hazy or bluish objects in the distance suggest they are farther away.

Top-Down Processes in Visual Interpretation

  • Traditional view: Visual processing flows bottom-up through sensory information.

  • Top-down processing integrates knowledge and expectations with sensory data.

Experiment by Steven Palmore (1975)

  • Context shapes object recognition:

    • Example: A loaf of bread identified correctly by 80%, whereas contextually inappropriate objects are less accurately recognized.

    • Suggests that context significantly impacts visual perception, reinforcing the necessity of both processes.

Pawson Paradox

  • Demonstrates the necessity of simultaneous bottom-up and top-down processing:

    • Disparate features (eyes, nose, mouth) can only be identified when considered together within a face.

Ecological Approach vs Inferential Approach

  • The inferential approach relies heavily on assumptions to interpret visual stimuli, which may lead to inaccurate representations of reality.

  • The ecological approach argues:

    • Abundant information exists in the environment that minimizes reliance on assumptions.

Examples of Ecological Information

  • Object Size Determination:

    • Poles at various distances intersecting the horizon line provides automatic size determination without conscious thought.

  • Motion and Optical Flow:

    • The visual system interprets relative motion of surrounding points of light as information for determining distance.

    • Example: When perceiving landscapes from a moving train, varying speeds of optically moving objects aid distance assessment.

Conclusion

  • The interaction of inferential methods and ecological information enhances understanding of visual processing.

  • Next video will focus on differences in processing and identification of faces and familiar objects.