Chapter 5- Sensory attentional and perceptual processes

1. Attention

Definition: The process of selecting certain stimuli from a group. Its properties include alertness, concentration, and search.

• Selective Attention: Focuses on limited stimuli. Influenced by internal factors (motivation, interest, cognitive style) and external factors (intensity, novelty, and complexity of stimuli).

• Sustained Attention (Vigilance): Ability to maintain focus for a long duration.
  Factors affecting it: sensory modality, clarity of stimuli, and spatial/temporal uncertainty.

2. Depth Perception

Definition: Viewing the world in three dimensions.

• Monocular Cues: Effective with one eye, e.g., relative size, interposition, linear perspective, and motion parallax.

• Binocular Cues: Depend on both eyes. Key cues include:

• Retinal Disparity: Difference between images seen by each eye indicates depth.

• Convergence: Eyes turn inward for nearby objects.

• Accommodation: Adjusting lens thickness for focusing.

3. Perceptual Processes

• Bottom-up Processing: Recognition starts with individual elements and builds to the whole.

• Top-down Processing: Recognition starts from the whole and breaks down into parts.

4. Illusions

Definition: Misinterpretation of sensory information, leading to a mismatch between perception and reality. Types include:

• Geometrical Illusions (e.g., Müller-Lyer Illusion)

• Apparent Movement Illusion (Phi-phenomenon)

5. Perceptual Constancies

• Size Constancy: Perceived size remains constant despite changes in distance.

• Shape Constancy: Familiar objects maintain their perceived shape.

• Brightness Constancy: Perceived brightness stays constant despite lighting changes.

6. Theories of Selective Attention

1. Filter Theory (Broadbent): Only one stimulus passes through a selective filter at a time.

2. Filter-Attenuation Theory (Triesman): Unselected stimuli are weakened but not blocked

3. Multimode Theory (Johnston & Heinz): Flexible selection at multiple stages (sensory, semantic, and conscious).

7. Principles of Perceptual Organization

• Proximity: Objects close together are grouped.

• Similarity: Similar objects are perceived as a group.

• Continuity: Objects forming a continuous pattern are grouped together.

• Smallness: Smaller areas are seen as figures against a larger background.

• Symmetry: Symmetrical shapes are perceived as complete figures.

• Surroundness: Surrounded areas are seen as figures, with the surrounding areas as background.

• Closure: Gaps in stimuli are filled to perceive a whole.