Sensation and Perception

What does the physical reality consist of?

all possible stimuli, including that beyond our
all possible stimuli including that beyond out science or ability to experience

All experienced reality is

subjective, shaped by genetics/past experiences,

how is reality coded by the CNS

1. receptors transduce stimuli into electricity

2. brain receives transduced info

3. mind creates consciousness,

what do illusions show us?

the mind is not determined by objective facts

dualism

the mind has an existance separate from the material world— Rene Descartes

Panpsychism

mind is the property of all matter (Wundt)

Distributed cognition

idea is mental processes that extend beyond the physical mind

Materialism

only matter exists, mind and consciousness are the results of interactions between bits of matter

Sensation

body’s ability to detect a stimulus; to transduce energy from the environment into neutral energy used by the brain

perception

assigning meaning to , understanding, interpreting sensations (SUBJECTIVE)

sensation physical example

visible light (electromagnetic radiation) is detected by structures in your eyes

perception example

at first: color and shape, then dog

What is sensation an example of?

bottom up process

What is perception an example of?

Top down process- brain is prediction machine never knowing objective realty, active construction

Vision

stimuli: electromagnetic radiation

receptors: photoreceptors in the eye

Physical dimensions humans can detect:

• light intensity

• wave length

• spatial distribution

• temporal distribution

Perceptual Dimensions:

• light brightness

• color

• shape, texture, and location in 3D

• motion

Audition

stimuli: sound pressure waves

receptors: hair cells in inner ear (cochlea)

Physical dimensions humans can detect:

• amplitude

• frequency

• waveform

• inter aural differences

Perceptual Dimensions:

• loudness

• pitch

• timbre

• location of sound source

Olfaction

stimuli: molecules

receptors: olfactory receptor neurons in nose

Physical dimensions humans can detect: molecular structure and concentration

Perceptual Dimensions: odor

Gustation

stimuli: molecules

receptors: taste receptors in mouth

Physical dimensions humans can detect: molecular structure and concentration

Perceptual Dimensions: sweetness, saltiness, biterness, sournes, etc.

touch

stimuli: mechanical forces

receptors: mechanoreceptors in skin

Physical dimensions humans can detect: skin indentation and stretch, motion, vibration of skin

Perceptual Dimensions: spatial pattern, texture, shape, hand conformation, etc.

Echolocation

helps judge distance from objects,

How do perceptions change from moment to moment and over the lifespan

• senses are either new stimuli becomes habituated

• some senses are innate

• some are informed by culture or experience

• occur across the lifespan to all senses

Gustav Fechner

invented psychophysics- true founder of experimental psyshology

psychophysics

the science of defining quantitave relationships between physical and psychological events

• sound pressure and perceived loudness

• light energy and perceived brightness

Two point touch threshold

minimum distance between two points of skin that can be distoinguied

just noticable difference

the smallest detectable difference

Absolute threshold

minimum amount of stimulation necessary for a person to detect stimulus 50% of the time

Ernst Weber

ernst weber discovered that the smallest detectable change is a constrant propotyion of the stimulus level

weber’s law

the principle describing the relationship between stimulus and resulting sensation that says the JND is a constant proportion of the stimulus

• larger stimulus values have larger JNDs and smaller stimulus values have smaller JNDs

Weber Fraction Example

if an individual was just able to tell differencde between a 100 and 102 gram object, they would just be able to discriminate 400 from 208 grams because it is just a 2% difference in weight

Fechner’s law

described the relationship between stimulus magnitude (intensity) and resulting sensation magnitude

• it takes larger and larger changes of physical intensitt to equal the same changes of sensation intensity