Sensation & Perception

Sensation

Process by which sensory receptors detect stimulus energies.

Sensory receptors

Specialized neurons that detect stimuli.

Perception

Organizing and interpreting sensory information.

Bottom-up processing

Starts with sensory input, builds up to perception.

Top-down processing

Uses prior knowledge/expectations to interpret input.

Transduction 

Conversion of stimulus energy into neural signals.

Psychophysics

Study of relationships between stimuli and sensations.

Fechner

Founder of psychophysics

Absolute threshold

Minimum stimulus needed to detect it 50% of the time.

Signal detection theory

Predicts how and when we detect faint stimuli amid noise.

Subliminal

Stimuli below absolute threshold; not consciously perceived.

Priming

Unconscious activation of associations.

Difference threshold

Minimum difference to detect change (just noticeable difference).

Weber

Studied difference thresholds.

Weber’s Law

Difference threshold is proportional, not fixed.

Sensory adaptation

Decreased sensitivity due to constant stimulation.

Wavelength

Distance between peaks of a wave; determines color or pitch.

Hue

Dimension of color determined by wavelength.

Intensity

Amount of energy in a wave; determines brightness/loudness.

Cornea

Transparent part of eye; bends light.

Pupil

Adjustable opening in eye.

Iris

Colored muscle that controls pupil size.

Lens

Focuses light on retina.

Retina

Light-sensitive inner surface of eye.

Accommodation

Lens changes shape to focus.

Rods

Retinal receptors for black/white/gray vision.

Cones

Retinal receptors for color and detail.

Optic nerve

Carries visual info to brain.

Blind spot

Area with no receptor cells where optic nerve leaves eye.

Fovea

Central focus point in retina; cones cluster here.

Trichromatic theory

Retina has three color receptors (red, green, blue).

Opponent-process theory

Opposing colors (red/green, blue/yellow, black/white) explain afterimages.

Hubel

Studied visual processing with Wiesel.

Wiesel

With Hubel, discovered feature detectors in visual cortex

Feature detectors

Neurons that respond to edges, angles, movement.

Parallel processing

Simultaneous analysis of visual input (motion, depth, color).