Psychology Chapter Sensory Processes

Sensory, Attentional, and Perceptual Processes

• Chapter Goal: Understand sensory processes, attention types, form/space perception, socio-cultural influences and everyday perceptual processes.
• Knowing the World: The world is full of objects, people, and events. Sensory receptors gather internal and external information.
• Nature and Varieties of Stimuli: External environment provides diverse stimuli (sights, sounds, smells, tastes, touch). Sensory receptors are specialized for different stimuli.
• Sensation: Initial experience of a stimulus by a sensory organ; process converts physical stimuli into electrical impulses.
• Sense Modalities: Eyes, ears, nose, tongue, skin are the primary external senses along with kinesthetic and vestibular senses. Each modality is specialized for different stimuli.
• Sensation Limitations: Sense organs have limited capacities e.g., eyes cannot see very dim or bright, ears cannot hear very faint or loud sounds.
• Absolute Threshold (AL): Minimum amount of stimulus needed to be detected.
• Difference Threshold (DL): Smallest difference between two stimuli that can be detected.
• Attentional Processes: Selecting from a number of stimuli, alertness, concentration, search. Attention filters certain stimuli.
• Selective Attention: Selecting/focusing on a limited set of stimuli from many available.
• Sustained Attention (Vigilance): Maintaining focus on a task or stimulus for a long period.
• Divided Attention: Allocating attention to multiple tasks simultaneously. (e.g driving and talking on the phone).

Perceptual Processes

• Processing Approaches:
  • Bottom-up Processing: Starting with sensory input; perception is a construction based on stimulus characteristics.
  • Top-down Processing: Prior knowledge, expectations, concepts influence perception; perception involves recognition/identification of stimuli.
• Perceptual Organisation: Gestalt psychologists; perception of "wholes" not just sum of parts.
  • Figure-Ground: Distinguishing figure from background.
  • Proximity: Grouping nearby objects.
  • Similarity: Grouping similar objects.
  • Continuity: Perception of continuous lines.
  • Closure: Filling in gaps to complete figures.
  • Symmetry: Perceiving symmetrical objects.
  • Common Region: Grouping objects in the same area as a figure.
• Depth and Distance Perception:
  • Monocular Cues: Used with one eye (e.g. linear perspective, relative size, interposition, texture gradient, relative height, light & shadow).
  • Binocular Cues: Used with two eyes (e.g. retinal disparity, convergence).
• Perceptual Constancies: Objects perceived as constant despite changes in sensory input. (e.g., size constancy, shape constancy, brightness);
• Illusions: Sensory misinterpretation or mismatch between physical stimuli and our perception of them.
• Socio-Cultural Influences: Cultural background and experiences influence perception. The way people perceive things can be influenced by their motivations, expectations, cultural background, experiences and beliefs.

Attention Deficit Hyperactivity Disorder (ADHD)

• ADHD is a behavioural disorder characterized by impulsivity, excessive motor activity, and inability to focus.
• More prevalent in boys than girls.
• Factors like home environment and family pathology are linked to ADHD.