SENSATION AND PERCEPTION

Sensation – the process of receiving information from the environment

Perception – our interpretation of what the incoming sensory info. means (WHAT WE MAKE OF IT)

*The first area of psychology studied – called Psychophysics (by G. Fechner)Before sensation can take place, sensory stimulation must meet threshold

Threshold – the amount of stimulation needed to trigger a neural impulse

“Bottom-up processing” – think of the sense as the bottom, the beginning of an experience

“Top-down processing” – complex brain interpretation (top of the body)

Absolute threshold – the minimum amount of stimulation needed to trigger a neural impulse 50% OF THE TIME

**THRESHOLD VARIES, BY PERSON, BY SITUATION

Signal detection – ability to detect a weak stimulus when extra effort is made

Each of the senses has an established, scientific absolute threshold

Just Noticeable Difference refers to the amount of change in the stimulus required before a difference is noticed

Weber’s Law is a mathematical formula for that concept

change in K (value for stimulus) K

A controversial threshold experience: subliminal stimulation

Started with an experiment by James Vicary in 1957The famous “Eat popcorn”, “drink Coca-Cola” experiment

Vicary admitted it was a hoax before he died!!

Read – sensory adaptation

The 5 senses:

1. Vision – the dominant senseLight – travels in waves, strikes an object, some wavelengths absorbed, others reflected back – the reflected light is what we perceive & labelProperties of light:

Wavelength = frequency(length) of wave (hue)

Amplitude = height of wave (intensity of color)

Transduction – process by which energy is converted into neural impulse – at the receptor level for each sense

Saturation – purity of wavelength

ROYGBIV

Structure of the eye:

1. Conjunctiva2. Cornea3. Sclera4. Iris5. Pupil

7. Lens8. Ciliary muscles & ligaments9. Vitreous humor

6. Aqueous humor

11. Retina12. Fovea centralis14. Optic Nerve13. Blind Spot

10. Choroid

Receptors in the retina: rods and conesCones:

used for color visionused for daylight visionlocated in center of the retinaapprox. 7 million each eyeprovide sharp, detailed visioncontain photochemicals called OPSINS

Rods:used for night visionused for white and blackheavily packed into the peripheral area of

retinaapprox. 120 million each eyeprovide rough outlines of shapes

4 layers

4 + layers of cells process neural impulse from rods/cones – bipolar, amacrine, horizontal and ganglion cells

B

A

G

H

Theories of color vision:1. Tri-chromatic Theory – Hermann Von Helmholtz

Retina has receptors with chemicals (opsins) which respond to ONLY 3 light waves

Those 3 lightwaves (ONLY) give us millions of hues

Feature detectors – Hubel and WieselParallel processing

Opponent Process Theory – Ewald Heringtrichromatic signals from the cones feed into neural cells (bipolar, ganglion, etc.) which fire in an opponent fashion – red/green blue/yellow or white/black

This explains the afterimage - *In an on-off way, not at the same time

When staring at ½ of color pair, it tires, and its opposite fires when you look away.

Humans are trichromatic – see all three color pairs8% of males are colorblind - dichromatic

Monochromatic – see in black, whit e and greys

2. Hearing (Audition)Sound travels in waves like light

Pitch is measured in Hertz (frequency)

- Normal human hearing range: 500 to 3,000 Hz (16-20,000 is possible)

Intensity (loudness) is measured in Decibels (amplitude)

-Noises above 130 can be painful-85 db on a daily basis can do damage

TINNITUS – ringing in the ears: a warning sign of hearing damage

Hearing loss usually begins in the high ranges

STRUCTURE OF THE EAR:

Outer ear:•Pinna•Auditory Canal

Tympanic Membrane – vibrates at freq. of sound waveMiddle Ear:

•Hammer (malleus)•Anvil (incus)•Stirrup(stapes)

Oval window – ditto TMInner ear•Cochlea •Basilar membrane contains hair cells

INCOMING SOUND WAVE

Hair cells: 20,000 per ear are attached to basilar membrane, wave back & forth in fluid.

That movement causes a an electrical impulse to fire in connected nerve cells

Hair cells do not regenerate!!! Damage them and they’re gone forever!!

Types of hearing loss:-Conductive deafness-Nerve (sensorineural) hearing lossTheories of pitch:

3. Cutaneous Sense (Touch) – also known as a somatosense

Only 3 types of receptors give us all of the sensations we experience:1. Pressure2. Temperature3. PainPain is least adaptive and necessary for survival!Babies and other animals deprived of touch are stunted physically, mentally and have high mortality rates

Pain fibers are smaller than temp. and pressure fibers. – body has both “slow” pain and “fast” pain cells

**More sensitive areas of body have more receptors

**Gate Control Theory – The spinal cord acts as a gate which can block the small slow pain fibers & release endorphins when pressure and/or temp. fibers are stimulated

Olfaction (smell)

*The most primitive sense – olfactory nerve is not routed through the thalamus

*The olfactory nerve is routed alongside the hippocampus, so smell is very evocative

Receptors are Olfactory bulbs – located high in nasal cavity in Olfatory Epithelium

Odor molecules lock into receptors sites on bulbs like key into lock – only scents with receptors can be registered

Smell is a chemical sense and a companion to taste

5. Gustation (taste)

Bumpy, porous surface of tongue - Papillae

Under that layer lie the receptors – Taste Buds

•Food must be in solution form to seep down to taste budsReceptors encircle the tongue, do not exist in the

center of the tongue

The types of receptors:Sweet, salty, sour, bitter and umami (savory)

Taste buds do regenerate!! They regenerate more slowly with age

ALL OF THE SENSES WORK IN COMBINATION IN A PROCESS CALLED SENSORY INTERACTION2 important companion senses:

*Kinesthetic sense - position of body and limbs

*Vestibular sense – system of semi-circular canals located in inner ear

-gives us our sense of equilibrium. Fluid in canals moves with our movement

These 2 + cutaneous sense give make up the somatosenses

PERCEPTIONPerceptual organization – studied by Gestalt psych. since mid-1800s

Grouping Principles:

http://graphicdesign.spokanefalls.edu/tutorials/process/gestaltprinciples/gestaltprinc.htm

*Proximity, similarity, continuity, closure and connectedness all contribute to patterns we perceive

Other Gestalt Principles: reversible figure and figure-ground

DEPTH PERCEPTION- Recognizing distance and 3 dimensional depth in space around us

A Nature or Nurture Issue!!Visual Cliff – test for depth perception in infants

- Created by Eleanor Walk and Richard Gibson

*Retinal disparity – the 2 ½ inch difference between the eyes creates 2 disparate images

1. BINOCULAR CUES – require both eyes

Brain overlaps/merges them - stereopsis

Depth cues:

*convergence – muscular cue: amount of tension created when eyes bring images together

•More strain – object is closer2. MONOCULAR CUES – only require 1 eye

•Interposition (overlap)•Relative size•Linear perspective•Aerial perspective (relative clarity)•Texture gradient•Relative height•Relative motion•Light & shadow

Linear perspective

Relative Height

Relative size

Perceptual ConstanciesSize constancy, shape constancy, color and brightness constancies all keep our world unchanging

Perceptual Set:-a predisposition to view the world from a particular perspective (a product of our schema)

Context Effects: perception is influenced by the situation/environment (also a product of schema)READ Perceptual Adaptation

ESP – 4 types:1. Telepathy2. Clairvoyance3. Precognition4. Psychokinesis

(telekinesis)

**PSYCHOLOGY DOES NOT SUPPORT ESP AS SCIENTIFIC PHENOMENON!!

Apparent motion:

Autokinetic effect, phi phenomena and stroboscopic motion