Sensation and Perception

Chapter 4 page 78

The 5 senses (sensory organs)

Sight (eyes) Hearing (ears) Smell (nose) Touch (skin) Taste (tongue)

Your 3 senses Select 3 things from each sense that you could

not live without. Select 1 from each that you could live without. Sights Sounds Tastes Feels Smells

Our Sensational Senses Defining sensation and perception The riddle of separate senses Measuring the senses Sensory adaptation Sensory overload

Chapter 4 section 1

Defining Sensation and Perception Sensation

The detection of physical energy emitted or reflected by physical objects.

It occurs when energy in the external environment or the body stimulates receptors in the sense organs.

Perception The process by which the brain organizes and

interprets sensory information.

Ambiguous Figure

Colored surface can be either the outside front surface or the inside back surface Cannot

simultaneously be both

Brain can interpret the ambiguous cues two different ways

The Riddle of Separate Sensations Sense receptors

Specialized cells that convert physical energy in the environment or the body to electrical energy that can be transmitted as nerve impulses to the brain.

Sensation & Perception Processes

Measuring Senses Absolute threshold Difference threshold

Absolute Threshold The smallest quantity of physical energy that can

be reliably detected by an observer.

Absolute Sensory Thresholds Vision:

A single candle flame from 30 miles on a dark, clear night Hearing:

The tick of a watch from 20 feet in total quiet Smell:

1 drop of perfume in a 6-room apartment Touch:

The wing of a bee on your cheek, dropped from 1 cm Taste:

1 tsp. Sugar in 2 gal. water

Difference Threshold The smallest difference in stimulation that

can be reliably detected by an observer when two stimuli are compared;

Sensory Adaptation and Deprivation Adaptation

The reduction or disappearance of sensory responsiveness when stimulation is unchanging or repetitious.

Prevents us from having to continuously respond to unimportant information.

Deprivation The absence of normal levels of sensory

stimulation.

Sensory Overload Overstimulation of the senses. Can use selective attention to reduce

sensory overload. Selective attention

The focusing of attention on selected aspects of the environment and the blocking out of others.

Section 2

Vision What we see An eye on the world Constructing the visual world

What We See Hue

Visual experience specified by colour names and related to the wavelength of light.

Brightness Lightness and luminance; the visual experience

related to the amount of light emitted from or reflected by an object.

Saturation Vividness or purity of colour; the visual

experience related to the complexity of light waves.

What We See

Hue Brightness Saturation

An Eye on the World Cornea

Protects eye and bends light toward lens.

Lens Focuses on objects

by changing shape. Iris

Controls amount of light that gets into eye.

Pupil Widens or dilates to

let in more light.

An Eye on the World Retina

Neural tissue lining the back of the eyeball’s interior, which contains the receptors for vision.

Rods Visual receptors that respond to dim light.

Cones Visual receptors involved in colour vision. Most

humans have 3 types of cones.

Afterimages

Test of Colour Deficiency

Constructing the Visual World Form perception Depth and distance perception Visual constancies: When seeing is

believing Visual illusions: When seeing is misleading

Form Perception Gestalt principles describe the brain’s

organization of sensory building blocks into meaningful units and patterns.

Figure and Ground Proximity

Seeing 3 pair of lines in A.

Similarity Seeing columns of

orange and red dots in B.

Continuity Seeing lines that connect

1 to 2 and 3 to 4 in C. Closure

Seeing a horse in D.

Depth and Distance Perception Binocular Cues:

Visual cues to depth or distance that require the use of both eyes.

Convergence: Turning inward of the eyes, which occurs when they focus on a nearby object.

Retinal Disparity: The slight difference in lateral separation between two objects as seen by the left eye and the right eye.

Depth and Distance Perception

Monocular Cues: Visual cues to depth or distance that can be

used by one eye alone.

The Ames Room A specially-built room

that makes people seem to change size as they move around in it

The room is not a rectangle, as viewers assume it is

A single peephole prevents using binocular depth cues

Visual Constancies The accurate perception of objects as stable

or unchanged despite changes in the sensory patterns they produce. Shape constancy Location constancy Size constancy Brightness constancy Colour constancy

Shape Constancy Even though these images cast shadows of

different shapes, we still see the quarter as round

Visual Illusions

Illusions are valuable in understanding perception because they are systematic errors. Illusions provide hints about perceptual strategies.

In the Muller-Lyer illusion (above) we tend to perceive the line on the right as slightly longer than the one on the left.

The Ponzo Illusion Linear perspective

provides context Side lines seem to

converge Top line seems farther

away But the retinal

images of the red lines are equal!

Fooling the Eye

The cats in (a) are the same size The diagonal lines in (b) are parallel You can create a “floating fingertip frankfurter” by

holding hands as shown, 5-10” in front of face.

Section 3

hearing

Hearing What we hear An ear on the world Constructing the auditory world

What We Hear Loudness

The dimension of auditory experience related to the intensity of a pressure wave.

Pitch The dimension of auditory experience related to

the frequency of a pressure wave. Timbre (pronounced “TAM-bur”)

The distinguishing quality of sound; the dimension of auditory experience related to the complexity of the pressure wave.

An Ear on the World

Auditory Localization Sounds from different

directions are not identical as they arrive at left and right ears Loudness Timing Phase

The brain calculates a sound’s location by using these differences.

Section 4

Other senses

Other Senses Taste: savory sensations Smell: The sense of scents Senses of the skin The environment within

The Taste Buds1. Bitter

2. Sour

3. Sweet

4. Salty

Taste: Savoury Sensations Papillae

Knoblike elevations on the tongue, containing the taste buds (Singular: papilla).

Taste buds Nests of taste-receptor cells.

Taste Buds Photograph of tongue

surface (top), magnified 75 times.

10,000 taste buds line the tongue and mouth. Taste receptors are

down inside the “bud”

Children have more taste buds than adults.

Four Tastes Four basic tastes

Salty, sour, bitter and sweet. Different people have different tastes based

on: Genetics Culture Learning Food attractiveness

Sense of smell

Smell: The Sense of Scents

Airborne chemical molecules enter the nose and circulate through the nasal cavity. Vapors can also enter through the mouth and pass into

nasal cavity. Receptors on the roof of the nasal cavity detect these

molecules.

Olfactory System

Sensitivity to Touch

The Environment Within Kinesthesis

The sense of body position and movement of body parts; also called kinesthesia.

Equilibrium The sense of balance.

Semicircular Canals Sense organs in the inner ear, which

contribute to equilibrium by responding to rotation of the head.

Perceptual Powers: Origins and Influences

Inborn abilities Critical periods Psychological and cultural Influences on

perception

The Visual Cliff

Glass surface, with checkerboard underneath at different heights Visual illusion of a cliff Baby can’t fall

Mom stands across the gap Babies show increased

attention over deep side at age 2 months, but aren’t afraid until about the age they can crawl (Gibson & Walk, 1960)

The Visual Cliff

Critical Periods If infants miss out on

experiences during a crucial period of time, perception will be impaired.

When adults who have been blind since birth have vision restored, they may not see well

Other senses such has hearing may be influenced similarly.

Psychological and Cultural Influences on Perception

We are more likely to perceive something when we need it.

What we believe can affect what we perceive. Emotions, such as fear, can influence perceptions

of sensory information. Expectations based on our previous experiences

influence how we perceive the world. Perceptual Set

A habitual way of perceiving, based on expectations.

All are influenced by our culture.

Perceptual Set

What you see in the centre figures depends on the order in which you look at the figures: If you scan from the left, see an old woman If you scan from the right, see a woman’s figure

Context Effects The same physical

stimulus can be interpreted differently

We use other cues in the situation to resolve ambiguities

Is this the letter B or the number 13?

Puzzles of Perception Subliminal Perception

Subliminal Perception Perceiving without awareness

visual stimuli can affect your behaviour even when you are unaware that you saw it

nonconscious processing also occurs in memory, thinking, and decision making

these effects are often small, however, and difficult to demonstrate and work best with simple stimuli

Subliminal Perception Perception versus Persuasion

there is no empirical research to support popular notions that subliminal persuasion has any effect on a person’s behaviour

persuasion works best when messages, in the form of advertising or self-help tapes, are presented above-threshold, or at a supraliminal level