UNIT 2: Sensation and Perception

Sensation

Detecting stimuli from the environment (bottom-up).

Perception

Organizing and interpreting sensory information (top-down).

Absolute Threshold

Minimum stimulation needed to detect a stimulus 50% of the time.

Difference Threshold (Just Noticeable Difference)

Smallest detectable difference between two stimuli.

Weber’s Law

To perceive a difference, stimuli must differ by a constant minimum percentage.

Signal Detection Theory

Predicts how and when we detect faint stimuli amid background noise based on experience, expectations, motivation, and fatigue.

Hit

Stimulus present and detected.

Miss

Stimulus present but not detected.

False Alarm

Stimulus absent but reported.

Correct Rejection

Stimulus absent and not reported.

Sensory Adaptation

Diminished sensitivity to a constant stimulus over time.

Transduction

Conversion of one form of energy into another, specifically converting stimulus energies into neural impulses.

Cornea

Protects the eye and bends light.

Pupil

Small adjustable opening in the eye.

Iris

Muscle that controls pupil size.

Lens

Focuses light on the retina.

Retina

Contains receptor cells (rods and cones).

Fovea

Central focus point in the retina with the highest concentration of cones.

Optic Nerve

Carries neural impulses to the brain.

Occipital Lobe (Visual Cortex)

Interprets visual information.

Rods

Photoreceptors responsible for peripheral vision and low light detection.

Cones

Photoreceptors responsible for color and detail in bright light.

Blind Spot

Area where the optic nerve leaves the eye with no receptors.

Young-Helmholtz Trichromatic Theory

Theory stating that three cones combine to form all colors.

Opponent-Process Theory

Theory explaining color perception through paired cells (red-green, blue-yellow, black-white).

Amplitude (sound)

Determines the loudness of sound.

Frequency (sound)

Determines the pitch of sound.

Decibels

Unit of loudness.

Outer Ear (Pinna)

Funnels sound into the ear.

Auditory Canal

Channel leading sound to the eardrum.

Eardrum (Tympanic Membrane)

Vibrates in response to sound.

Cochlea

Fluid-filled structure where transduction occurs via hair cells.

Place Theory

Theory that explains how different pitches stimulate different parts of the cochlea.

Frequency Theory

Theory that relates the firing frequency of the auditory nerve to the pitch of sound.

Gate-Control Theory

Theory explaining that the spinal cord can block or allow pain signals.

Kinesthesia

Sense of body part movement and position.

Vestibular Sense

Sense controlling balance and head position.

Taste (Gustation)

Involves five basic tastes: sweet, salty, sour, bitter, umami.

Smell (Olfaction)

Only sense that bypasses the thalamus, involving receptors in the nose.

Figure-Ground

Organizational principle where the object is seen as the figure and the background as ground.

Retinal Disparity

Binocular cue for depth perception based on differences between images from both eyes.

Monocular Cues

Depth cues available to either eye alone.

Shape Constancy

Perception of the same shape despite changes in angle.

Extrasensory Perception (ESP)

Perception that occurs outside of the usual sensory channels.