PSY 324 Exam 3 - Detailed Version

Realism

The belief that the world exists as it is, independent of perception.

Positivism

The belief that knowledge should be based on observable, measurable phenomena.

Euclidean geometry

Study of points, lines, and planes with principles like parallel lines never meeting and the sum of angles in a triangle = 180°.

Why eyes don't adhere to Euclidean geometry

Human vision is curved and perspective changes with distance; retinal images are not perfect Euclidean projections.

Advantages of two eyes in front of the head

Allows depth perception, binocular vision, better focus on objects, and overlaps visual fields for stereopsis.

Disadvantages of two eyes in front

Reduced peripheral vision compared to side-placed eyes.

Field of vision with forward eyes

Overlapping fields improve depth perception; peripheral coverage is narrower.

Binocular disparity

The slight difference in images between the two eyes that allows depth perception.

Corresponding points

Points on each retina that would overlap if images were superimposed; objects here have zero binocular disparity.

Horopter

Imaginary surface where objects fall on corresponding points and appear single; objects off it may appear doubled.

Crossed disparity

Objects in front of the horopter; images displaced outward relative to each eye.

Uncrossed disparity

Objects behind the horopter; images displaced inward relative to each eye.

Stereopsis

Depth perception derived from binocular disparity.

Stereopsis from 2D stimuli

Achieved with VR, 3D movies, or free fusion of 2D images.

Monocular depth cue

Depth info from a single eye (e.g., linear perspective, texture gradient, interposition).

Metric monocular cue

Provides quantitative depth info (exact distance measurements).

Nonmetric monocular cue

Provides qualitative depth info (order or relative depth, not exact distance).

Accommodation

Lens changes shape to focus light on the retina; cue for depth at close distances.

Convergence

Eyes rotate inward to focus on near objects; cue for depth.

Divergence

Eyes rotate outward to focus on distant objects; cue for depth.

Correspondence problem

Determining which features in the left-eye image match features in the right-eye image.

Solving the correspondence problem - uniqueness constraint

Each feature is represented only once on each retina.

Solving the correspondence problem - continuity constraint

Neighboring points usually lie at similar distances, except at edges.

Bayesian approach in vision

Brain combines prior knowledge with sensory input to estimate the most likely scene interpretation.

Visual illusions

Errors in depth perception caused by misinterpretation of combined cues (e.g., accidental viewpoint, penny example).

Accidental viewpoint

Viewing a scene from an unusual angle causing misperception.

Penny example

Brain uses prior knowledge to interpret depth, even from partial cues.

Free fusion

Crossing eyes or aligning two 2D images to create a stereoscopic 3D perception.

Strabismus

Misalignment of eyes; esotropia (inward), exotropia (outward).

Strabismus in adults

Causes double vision.

Strabismus in children

Brain suppresses one eye to avoid double vision.

Sound

Vibration of objects causing pressure changes in a medium (air, water).

Speed of sound in air

~340 m/s.

Speed of sound in water

~1500 m/s; faster because water is denser.

Frequency of a sound

Number of cycles per second (Hz); perceived as pitch.

Amplitude of a sound

Magnitude of pressure change; perceived as loudness.

Human hearing range (frequency)

20-20,000 Hz.

Human hearing range (amplitude)

0-120 dB.

Decibel (dB)

Logarithmic measure of sound pressure ratio; +6 dB ≈ double pressure.

Simple sound (pure tone)

Single sine wave; rare in real life.

Complex sound

Combination of multiple frequencies; includes fundamental frequency and harmonics.

Timbre

Characteristic allowing us to distinguish sound sources; determined by harmonics.

Outer ear - pinna

Collects sound waves.

Outer ear - ear canal

Funnels sound to tympanic membrane.

Tympanic membrane

Vibrates in response to sound.

Middle ear - ossicles

Malleus, incus, stapes; amplify sound for fluid transmission.

Middle ear - tensor tympani & stapedius

Muscles that protect against loud sounds.

Inner ear - oval window

Entrance from middle ear to cochlea.

Cochlea

Snail-shaped structure with fluid-filled canals; transduces sound.

Organ of Corti

Contains basilar membrane and hair cells; converts vibrations to neural signals.

Inner hair cells

One row; send info to brain (afferent).

Outer hair cells

Three rows; receive info from brain (efferent); enhance frequency sensitivity.

Tectorial membrane

Sits above inner hair cells and on outer hair cells; shearing opens ion channels.

Hearing pathway

Sound → pinna → ear canal → tympanic membrane → ossicles → oval window → cochlear fluid → basilar membrane → hair cells → auditory nerve.

Auditory coding - amplitude

Higher amplitude → higher firing rate.

Auditory coding - frequency (temporal)

Firing rate matches sound wave frequency (phase-locking).

Auditory coding - frequency (place)

Different frequencies activate different locations on basilar membrane.

Rate saturation

Maximum firing rate of neuron; cannot increase beyond this point.

Two-tone suppression

Response to one tone is reduced by simultaneous second tone.

Auditory processing order

Cochlea → cochlear nucleus → superior olivary complex → inferior colliculus → medial geniculate nucleus → auditory cortex.

Medial geniculate nucleus (MGN)

Thalamic relay for auditory info; organized by frequency (tonotopic).

Auditory cortex

Processes complex sounds, pitch, and spatial location.

Conductive hearing loss

Impaired sound conduction through outer or middle ear (e.g., earwax, otitis media, otosclerosis).

Sensorineural hearing loss

Damage to hair cells or auditory nerve; affects perception of pitch and loudness.

Sound localization - timing

Interaural time difference (ITD) helps locate sounds horizontally.

Sound localization - intensity

Interaural level difference (ILD) helps locate sounds; more effective for high frequencies.

Cone of confusion

Regions where ITD and ILD cues are ambiguous; resolved by head movement or pinna shape.

Distance cues for sound

Relative intensity, spectral composition (high frequencies fade faster), and direct vs. reverberant energy.