Perceptual organization

• How do we form meaningful perceptions from sensory information?

Gestalt psychology

• Branch of cognitive psychology• Organization of many sensations into

perceptions of wholes– Gestalt = whole or form

• Based on experience and expectations• Perceived whole is not always the same

as its parts!

Form perception

• Simplification into easily interpretable wholes

• Figure-ground

Form perception

• Grouping principles– Proximity– Similarity– Continuity– Connectedness– Closure

Depth perception

• Distance is perceived with vision and hearing

• Visual depth perception– Binocular cues– Monocular cues

Binocular depth cues

• Retinal disparity– Strongest visual depth cue

Monocular depth cues

• Light and shadow• Relative size and

position• Relative

height/vertical position

• Linear perspective

Auditory location cues

• Intensity and pitch• Arrival times at each ear• Clarity

Perceptual constancy

• Cognitive functions that maintain the features of an object, despite changing illumination, color, size, or shape– Based on comparisons between the figure

and ground

Color and lightness constancy

• Consistent color and light intensity, despite changes in illumination

Shape and size constancy

• Familiar objects are perceived as unchanging despite changes in retinal images.

Perceptual interpretation

• Making sense of the perceptions produced by the cortex– Genetics– Experience

• Critical periods• Plasticity and adaptation

Perceptual set

• Psychological predisposition to perceive stimuli in a particular way– Shaped by learned assumptions and beliefs– Affects how we interpret sensory stimuli

• Examples

Other sensory modalities

Hearing

• Stimulus - sound waves– Frequency– Amplitude

The ear

Auditory stimuli

• Bending of hair cells in the cochlea transduces vibrations into neural signals

• Auditory nerve• Primary

auditory cortex• Auditory

association cortex

Touch

• Stimulus - pressure, pain, warmth, cold– Receptors– Other sensations

• Stimuli organized in primary somatosensory cortex

• Perceptions created in somatosensory association cortex

Pain

• Critical alert system• Subjective

– Physiology– Prior experiences– Attention– Context– Culture

Pain

• Gate-control theory

• Pain control/management

Taste

• Stimulus - chemical molecules that impart the sensations of sweet, sour, salty, bitter and umami

• Tastebuds contain taste and touch receptors

Sweet Sour Salty Bitter Umami

Taste perception

• Flavor – Based on taste, olfactory, and touch stimuli

• Begins in brainstem• Completed in the limbic system

Taste preferences

• Genetic predisposition

• Biological predisposition

• Learned responses

Smell

• Stimulus - chemical molecules • Receptors in olfactory epithelium

– Axons project directly to the olfactory bulb of the brain

– Perception begins in the olfactory bulb, completed in the limbic system

Kinesthesis & vestibular sense

• Kinesthesis - sense of body position and movement

• Vestibular sense - sense of head postion and movement

• Stimulus - gravity and movement• Receptors found in muscles (body) and

inner ear (head)

Kinesthesis & vestibular sense

• Sensory signals about position and movement are organized in the medulla and cerebellum

• Perception occurs throughout the brain– Brain stem– Temporal cortex