Sensory process & perception

Eesha Sharma, MD

Sense organs

Receptor potentialGenerator potential

Psychophysics• Gustav Theodor Fechner, 1860

• Quantitative relationship between physical stimuli and the sensations and perceptions they effect– Subject’s experience or behavior

• Objectively measurable stimuli– Absolute thresholds– Discrimination thresholds– Scaling

Experience

Sensation

Perception

Apperception

Perceptual processes

• Attention• Form perception• Visual depth perception• Constancy• Movement perception• Plasticity• Individual differences

Attention

• The perceptual process that selects certain inputs for inclusion in our conscious experience, or awareness, at any given time

Filtering

Parallel processing

Serial processing

Processing capacity

Form perception

• Recognition of a figure on a ground

Contours

Organization

• Gestalt: The whole is more than the sum of its parts• Laws of perceptual organization– Proximity– Similarity– Symmetry or good figure– Continuation– Closure

Visual depth perception

• Monocular cues– Linear perspective– Clearness– Interposition– Shadows– Gradients of texture– Movement

• Binocular cues– Retinal disparity

Constancy

• Size constancy– Results when the object and its background change

together in such a way that the relationship between them stays the same

– Moon in the night sky

• Brightness constancy– Result of unchanged brightness ratios

Movement perception

• Real motion perception– Constancy: because of unchanged relationship between

object and its background– The brain comparator

• Apparent motion– Stroboscopic motion– Autokinetic effect– Induced movement

Plasticity

• Visual deprivation– Sensitive period– Nature and nurture

Individual differences• Perceptual learning– An increase in the ability to extract information from the

environment as a result of experience or practice with the stimulation coming from it

– Ornithologists; Blind people• Set– Readiness or priming for certain kinds of sensory input

• Motives and needs– Rorschach inkblots

• Perceptual-cognitive style– Flexibility– Field dependence