Visual Perception,

Visual Illusions,

and

Hearing

Be able to recognize:

1. Perceptual sets and Gestalt principles of visual perception.

2. Cues for depth perception, perceptual constancies, and

examples of optical illusions and impossible figures.

3. The auditory system

4. Hearing and parts of the ear

5. The auditory pathway

6. Auditory localization

7. Preventable hearing problems and deafness

Objectives

The area of perception connects

Psychology’s to its roots in Philosophy:

8-Bit Philosophy’s Take

Principles of Perception

• Gestalt principles of form perception help explain

how people subjectively organize perception:

– Phi phenomenon Create illusion of movement by presenting visual stimuli

in rapid succession

– Figure-ground Part of a stimulus stands out as a figure (object) against a

less prominent background (ground)

– Proximity These dots might well be organized in vertical columns

rather than horizontal rows, but because of proximity (the

dots are closer together horizontally), they tend to be

perceived in rows

– Similarity Because of similarity of color, in example you see dots

organized into the number 2 instead of a random array. If

you did not group similar elements, you wouldn’t see the

number 2 here.

( adapted from Cengage, 2019)

Gestalt Principles of Perception (continues)

– Continuity You tend to group these dots in a way that produces a

smooth path rather than an abrupt shift in direction

– Closure Even though the figures are incomplete, you fill in the

blanks and see a circle and a dog.

– Simplicity You could view this as a complicated 11-sided figure, but

given the preference for simplicity, you are more likely to

see it as a rectangle and a triangle.

( adapted from Cengage, 2019)

The principle of figure and ground

Figure 4.19 Gestalt principles of perceptual organization

This visual effect is

known as pop-out.

Pop-out occurs

because the visual

system is highly

sensitive to

elementary visual

features, such as

colors, shapes, and

lines. Identification

of such features

appears to take

place very early in

the processing of

visual information.

(Adapted from

Ramachandran,

1992b.) Pop-out is

so basic that babies

as young as 3

months respond to

it (Quinn & Bhatt,

1998).

(adapted from Wadsworth/Thomson Learning, 2001)

Stability in the Perceptual World: Perceptual Constancies

• Perceptual constancies – stable perceptions amid changing stimuli – Size

– Shape

– Brightness: Apparent brightness of an object stays the same under changing lighting conditions

– Hue

– Location in space

(adapted from Cengage, 2019)

Perceptual Grouping

• Context

• Reversible Figure: Figure and ground can be

reversed

( adapted from Cengage, 2019)

(adapted from Wadsworth/Thomson Learning, 2001)

A famous

reversible

figure.

( adapted from Thomson Higher Education, 2007)

The Necker Cube

Optical Illusions: The Power of Misleading Cues

• Optical Illusions - discrepancy between visual

appearance and physical reality.

• Famous optical illusions: Muller-Lyer Illusion,

Ponzo Illusion, and impossible figures

( adapted from Cengage, 2019)

(adapted from Wadsworth/Thomson Learning, 2001)

The Ponzo

Illusion

Three Classic Impossible Figures

Drawn by Shepard (1990)

(adapted from Wadsworth/Thomson Learning, 2001)

Depth Perception

• Definition: Ability to see three dimensional

space and to accurately judge distances

• Depth Cues: Features that supply

information about distance and space

(adapted from Cengage, 2019)

Depth and Distance Perception

• Binocular cues – clues from both eyes together

– retinal disparity

– convergence

• Monocular cues – clues from a single eye

– Example: pictorial depth cues

( adapted from Cengage, 2019)

Convergence and Depth Perception. One binocular depth cue is convergence. The more

you have to converge your eyes together to focus on an object, the closer the object must be.

(adapted from Wadsworth/Thomson Learning, 2001)

(a) Linear perspective. (b) Relative size. (c) Light and shadow. (d) Overlap. (e) Texture

gradients. Drawings in the top row show fairly “pure” examples of each of the pictorial depth

cues. In the bottom row, the pictorial depth cues are used to assemble a more realistic scene.

(adapted from Wadsworth/Thomson Learning, 2001)Example

Hearing: The Auditory System

• Stimulus = sound waves (vibrations of molecules traveling in air)

• Amplitude (loudness)

• Wavelength (pitch)

• Purity (timbre)

• Wavelength described in terms of frequency: measured in cycles per second (hertz; Hz)

• Frequency increase = pitch increase

( adapted from Thomson Higher Education, 2007, 2001)

(adapted from Wadsworth/Thomson Learning, 2001)

The Ear: Three Divisions

• External ear (pinna): Collects sound

• Middle ear: The ossicles (hammer, anvil,

stirrup)

• Inner ear: The cochlea - a fluid-filled, coiled

tunnel

• contains the hair cells, the auditory receptors

• lined up on the basilar membrane

( adapted from Thomson Higher Education, 2007, 2001)

The Auditory Pathway

• Sound waves vibrate bones of the middle ear

• Stirrup vibrates against oval window of cochlea

• Fluid inside cochlea is set in motion, which moves the basilar membrane

• Hair cells on surface of basilar member are stimulated by this movement

• Physical stimulation converted into neural impulses

• Sent through the thalamus to the auditory cortex (temporal lobes)

(adapted from Wadsworth/Thomson Learning, 2001)

(adapted from Wadsworth/Thomson Learning, 2001)

Example

Auditory Localization: Where Did a Sound Come From?

• Two cues critical:

• Intensity (loudness)

• Timing of sounds arriving at each ear

– Head as “shadow” or partial sound barrier

• Timing differences as small as 1/100,000 of a

second

(adapted from Wadsworth/Thomson Learning, 2001)

(adapted from Wadsworth/Thomson Learning, 2001)

(adapted from Wadsworth/Thomson Learning, 2001)

Example:

Noise &

Hearing Loss

Context:

• Heavy-equipment

operators

• Frequent exposure

to noise levels from

90 – 120 db

• Hearing test results

compared with

estimates of “typical”

hearing for similar

age groups

(cf. Muchinsky, 1987)

Hearing Problems

• Stimulation Deafness: Damage caused by

exposing hair cells to excessively loud sounds.

– Typical at rock concerts

• Tinnitus: Ringing or buzzing sensation in the ears

(adapted from Wadsworth/Thomson Learning, 2001)

(adapted from Wadsworth/Thomson Learning, 2001)

Other Forms of Deafness

• Conduction Deafness: Poor transfer of sounds

from tympanic membrane to inner ear

– Compensate with amplifier (hearing aid)

• Nerve Deafness: Caused by damage to hair cells

or auditory nerve

– Hearing aids useless in these cases, since auditory

messages cannot reach the brain

– Cochlear Implant: Electronic device that stimulates

auditory nerves

(adapted from Wadsworth/Thomson Learning, 2001)