Chapter 4 Psychology: From Inquiry to Understanding

Sensation and Perception

illusion

perception in which the way we perceive a stimulus doesn’t match its physical reality

Sensation

detection of physical energy by our sense organs, including our eyes, ears, skin, nose, and tongue, which then relay information to the brain.

Ex. it hurts when you hit the corner of the table

Perception

the brain’s interpretation of raw sensory inputs.

Ex. You eat an ice cream and feel extra cool.

Transduction

the process of converting an external energy or substance into electrical activity within neurons

Ex. External stimulus -(Sense receptors (specialized cell))→ electrical signal

Sensory receptors

specialized cell responsible for converting external stimuli into neural activity for a specific sensory system

Absolute Threshold

lowest level of a stimulus needed for the nervous system to detect a stimulus 50 percent of the time

German scientist Gustav Fechner

published a landmark work on perception

Psychophysics

the study of how we perceive sensory stimuli based on their physical characteristics

just noticeable difference (JND)

the smallest change in the intensity of a stimulus that we can detect

Weber’s Law

the stronger the stimulus, the bigger the change needed for a change in stimulus intensity to be noticeable

relationship is proportional

Signal detection theory

describe how we detect stimuli under uncertain conditions, as when we’re trying to figure out what a friend is saying while loud music is playing—that is, when there’s high background noise.

Signal-to-noise ratio

harder to detect a signal as background noise increases

Distinguishing Signals from Noise

Selective attention

process of selecting one sensory channel and ignoring or minimizing others

Cocktail party effect

reflects our ability to hone in on one stimulus, such as a conversation we’re engaged in, while we filter out other stimuli such as music or other conversations in a noisy room.

Inattentional blindness

failure to detect stimuli that are in plain sight when our attention is focused elsewhere

Change Blindness

a failure to detect obvious changes in one’s environment

The Binding Problem

One of the great mysteries of psychology. When we perceive an apple, different regions of our brains process different aspects of it. Yet somehow—we don’t really know how—our brains manage to combine or “bind” these diverse pieces of information into a unified whole. An apple looks red and round, feels smooth, tastes sweet and tart, and smells, well, like an apple. Any one of its characteristics in isolation isn’t an apple or even a part of an apple.

Hue

color of light

Sclera

white portion of the eye

Iris

colored part of the eye and is usually blue, brown, green, or hazel

Pupil

circular hole through which light enters the eye

Cornea

part of the eye containing transparent cells that focus light on the retina

Lens

part of the eye that changes curvature to keep images in focus

Retina

membrane at the back of the eye responsible for converting light into neural activity

Nearsightedness, myopia

results when images are focused in front of the rear of the eye due to our cornea being too steep or our eyes too long

Farsightedness, or hyperopia

results when our cornea is too flat or our eyes too short

Fovea

central portion of the retina

Optic Nerve

Transmits visual information from the retina and the brain

Blind Spot

part of the visual field we can’t see because of an absence of rods and cones

trichromatic theory

idea that color vision is based on our sensitivity to three primary colors

Color Blindness

most often due to the absence or reduced number of one or more types of cones stemming from genetic abnormalities.

monochromats

who have only one type of cone and thereby lose all color vision—are extremely rare, making up only about 0.0007 percent of the population.

Dichromats

they have two cones and are missing only one.

Opponent Process Theory

theory that we perceive colors in terms of three pairs of opponent colors: either red or green, blue or yellow, or black or white

*Explains what Trichromatic theory cannot

*3 pairs of opponent cells that work in opposition: red or green, blue or yellow, or black or white

Blindness

• rely on other senses more heavily

• Brain may repurpose visual cortex

Blindsight

blind people performing above-chance on visual tasks

happens without conscious awareness

Audition

our sense of hearing

Sound

a vibration, a kind of mechanical energy traveling through a medium, usually air

Pitch

wave frequency

• higher frequency=high pitch

• lower frequency=lower pitch

Timbre

complexity or quality of sound that makes musical instruments, human voices, or other sources sound unique

Loudness

amplitude of the sound waves

• higher amplitude=short wavelengths

• Lower amplitude=long wavelengths

Outer ear

consists of the pinna, and ear canal, has the simplest function; it funnels sound waves onto the eardrum

Cochlea

in the inner ear, converts vibration into neural activity.

The outer part is spiral-shaped and bony, but its inner cavity is filled with a thick fluid. Vibrations from sound waves disturb this fluid and travel to the base, where pressure is released and transduction occurs.

Middle ear

containing the ossicles—the three tiniest bones in the body—named the hammer, anvil, and stirrup, after their shapes. These ossicles vibrate at the frequency of the sound wave, transmitting it from the eardrum to the inner ear.

Pitch Perception

Place Theory

Base=high pitch

Top=low pitch

Only accounts for high-pitched tones

Frequency Theory

neurons rate of firing reproduces the frequency of the sound.

Only accounts for very low pitches.

Volley Theory

Sets of neurons fire together at their maximum rate to produce higher pitches