Sensation and Perception Weiten Chapter 4

sensation

The stimulation of sense organs.

perception

The selection, organization, and interpretation of sensory input.

psychophysics

The study of how physical stimuli are translated into psychological experience.

threshold

A dividing point between energy levels that do and do not have a detectable effect. Eg., A lamp that automatically turns on when a room gets dark. The level of light intensity at which the gadget clicks on is its .................. ?

absolute threshold

For a specific type of sensory input, the minimum stimulus intensity that an organism can detect.

just noticeable difference

The smallest difference in stimulus intensity that a specific sense can detect.

signal detection theory

Proposes that the detection of stimuli involves decision processes as well as sensory processes, which are both influenced by a variety of factors besides stimulus intensity.

subliminal perception

The registration of sensory input without conscious awareness.

sensory adaptation

A gradual decline in sensitivity to prolonged stimulation. Eg., Smelly garbage in a room smells awful upon entering, the smell is perceived to fade over time, but really the stimulus intensity of the odor is actually stable.

lens

The transparent eye structure that focuses the light rays falling on the retina.

accommodation

Occurs when the curvature of the lens adjusts to alter visual focus.

amplitude

Light waves vary in height. Related perception is brightness.

wavelength

The distance between peaks in light waves. Related perception is hue (colour).

purity

Influences perception of the saturation, or richness, of colours (how varied he mix is).

saturation

Refers to the relevant amount of whiteness in a colour. The intensity of colour.

nearsightedness

Close objects are seen clearly but distant objects appear blurry because the focus of the light from distant objects falls a little short of the retina.

farsightedness

Distant objects are seen clearly but close objects appear blurry because the focus of light from close objects fall behind the retina.

iris

Controls the amount of light entering the eye because it controls the size of the pupil (The coloured part of the eye).

pupil

The opening in the center of iris that permits light to pass into the ear chamber of the eye (The black part of the eye).

retina

The neural tissue lining the inside back surface of the eye; it absorbs light, processes images, and sends visual information to the brain.

optic disk

The axons that run from the retina to the brain converge here: A hole in the retina where the optic nerve fibers exit the eye.

cones

Specialised visual receptors that play a key role in daylight vision and colour vision.

fovea

When you want to see something sharply, you usually move your eyes so the object is centered in the:
Tiny spot in the center of the retina that contains only cones; visual acuity is greatest at this spot.

rods

Specialised visual receptors that play a key role in night vision and peripheral vision.

dark adaptation

The process in which the eyes become more sensitive to light in low illumination. Entering a dark theatre on a sunny day, you stumble around blindly.

light adaptation

The process whereby the eyes becomes less sensitive to light in high illumination. Leaving a dark theatre, entering a sunny day and having to squint to ward off the overwhelming brightness.

optic nerve

A collection of axons from ganglion cells that connect the eye with the brain. These axons depart from the eye through the optic disk, carry visual information, encoded as a stream of neural impulses, to the brain.

receptive field

The retinal area that, when stimulated, affects the firing of that cell.

lateral antagonism

Occurs when neural activity in a cell (from light) opposes activity in surrounding cells.

optic chiasm

The point at which the optic nerves from the inside half of each eye cross over and then project to the opposite half of the brain.

main

The visual pathway that processes the perception of form, colour, brightness, contrast and depth.

secondary

The visual pathway that processes the localisation of objects, coordination with other sensory input.

feature detectors

Neurons that respond selectively to very specific features of more complex stimuli. Cells in the visual cortex seem to be highly specialised.

red

In the visible spectrum, lights with the longest wavelengths appear........

violet

In the visible spectrum, lights with the shortest wavelengths appear........

subtractive colour mixing

Works by removing some wavelengths of light, leaving less light than was originally there. E.g., by mixing yellow and blue paints, causes pigments to absorb wavelengths, giving rise to the perception of green.

additive colour mixing

Works by superimposing lights, putting more light in the mixture than exists in any one light by itself. E.g., by shining red, green, and blue spotlights on a white surface, you'll have an additive mixture.

trichromatic theory

Holds that the human eye has three types of receptors with differing sensitivities to different light wavelengths (green, red and blue).

colour blindness

A variety of deficiencies in the ability to distinguish among colours.

complementary colours

Pairs of colours that produce gray tones when mixed together.

afterimage

A visual image that persists after a stimulus is removed.

opponent process theory

Holds that colour perception depends on receptors that make antagonistic responses to three pairs of colours (red vs green, yellow vs blue and black vs white).

both

Which theory should be used to explain colour vision? Trichromatic or Opponent Process Theory?

reversible figure

A drawing that is compatible with two interpretations that shift back and forth. Key point: The same visual stimuli can produce different perceptions.

perceptual set

A readiness to perceive a stimulus in a particular way (priming before presented an image). Creates a certain slant to how someone interprets sensory input.

inattentional blindness

Involves the failure to see visible objects or events because one's attention is focused elsewhere.

feature analysis

The process that assumes bottom-up processing, by detecting specific elements in visual input and assembling them into a more complex form. E.g., starting with lines, edges and corners and build them into more complex perceptions such as a bike or a telep

bottom-up processing

Feature analysis assumes a progression from individual elements to the whole.

top-down processing

Subjective contours assumes a progression from the whole to the elements

subjective contours

Involves the perception of contours where none actually exist. Eg., Showing the contours of a triangle, even with no physical edges or lines present, we can see the image of a triangle.

Gestalt

The whole can be greater than the sum of its parts".

phi phenomenon

The illusion of movement created by presenting visual stimuli in rapid succession.

proximity

Gestalt principle says that elements that are close to one another tend to be grouped together. E.g., People tend to notice that the dots are in rows as opposed to columns because they are closer together in the rows.

closure

Gestalt principle says that viewers tend to supply missing elements to close or complete a familiar figure.

similarity

Gestalt principle says that elements that are similar tend to be grouped together. Eg., Many random circles are displayed, but the viewer can make out the number 2 figure because some of the circles are similar colours (in the shape of 2).

simplicity

Gestalt principle says that viewers tend to organize elements in the simplest way possible. E.g., The complex looking picture is really is just a rectangle and a triangle that are overlapping.

continuity

Gestalt principle says that viewers tend to see elements in ways that produce smooth continuation.

distal stimuli

The stimuli that lie in the distance (in the world outside the body). They are the objects that you are looking at, they are distant in that your eyes do not touch them.

proximal stimuli

The stimulus energies that impinge directly on sensory receptors. There are great differences between the objects you perceive and the stimulus energies that represent them.

perceptual hypothesis

Making an inference about which distal stimuli could be responsible for the proximal stimuli sensed. E.g., From a distance you perceive an object to look like a rectangle (proximal stimuli) but your perceptual system 'guesses' it's actually a square (dist

depth perception

Involves interpretation of visual cues that indicate how near or far away objects are.

binocular

Cues about distance based on the differing views of the two eyes.

retinal disparity

The principle binocular depth cue which refers to the fact that objects within 25 feet project images to slightly different locations on the right and left retinas, so the right and left eyes see slightly differing views of the object. The closer the obje

convergence

A binocular cue which involves sensing the eyes converging toward each other as they focus on closer objects.

monocular

Cues about distance based on the image in either eye alone.

motion parallax

A monocular cue which involves images of objects at different distances moving across the retina at different rates. (Close objects appear to move rapidly while distance objects appear to move slowly).

pictorial depth cues

Monocular cues that give clues about distance that can be given in a flat picture.

linear perspective

A pictorial depth cue reflecting the fact that lines converge in the distance.

textual gradients

A pictorial depth cue that shows texture gradually becomes denser and less distinct.

interposition

A pictorial depth cue that if an object comes between you and another object, it must be closer to you.

relative size

A pictorial depth cue that closer objects appear larger.

height in plane

A pictorial depth cue that reflects the fact that distant objects appear higher in a picture.

light and shadow

A pictorial depth cue that patterns of light and dark suggest shadows that can create an impression of three dimensional forms.

perceptual constancy

A tendency to experience a stable perception in the face of a continually changing sensory input E.g., while walking closer to an object you don't perceive it as growing larger.

visual illusion

Involves an apparently inexplicable discrepancy between the appearance of a visual stimulus and its physical reality.

impossible figures

Objects that can be represented in two-dimensional pictures but cannot exist in three-dimensional space (2d optical illusions).

amplitude

Sound waves vary in height. Related perception is loudness.

wavelength

The distance between peaks in sound waves. Related perception is pitch. This is also described as frequency.

purity

The complexity of a sound. Related perception is timbre. To understand timbre, think of a note with precisely the same loudness and pitch played on a French horn and the violin. The difference you perceive in the sound is a difference in timbre.

hertz

Sound frequency is measure in?

decibels

Sound amplitude is measured in?

ossicles

The middle ear contains the hammer, anvil and stirrup. Also known as?

cochlea

The inner ear largely consists of a fluid-filled, coiled tunnel that contains the receptors for hearing.

oval window

Sound enters the cochlea through the ........... ............, which is vibrated by the ossicles.

basilar membrane

Runs the length of the spiraled cochlea, contains the auditory receptors.

place theory

Theory that perception of pitch corresponds to the vibration of different portions, or places along the basilar membrane.

frequency theory

Theory that perception of pitch corresponds to the rate, or frequency, at which the entire basilar membrane vibrates.

both in part

Which theory of pitch perception is valid. Place theory or frequency theory?

volley principle

Holds that groups of auditory nerve fibers fire neural impulses in rapid succession, creating volleys of impulses. These volleys exceed the 1000-per-second limit.

auditory localisation

Locating the source of a sound in space.

opponent process theory

Which theory of colour vision best explains why the colour of an afterimage is the complement of the original colour?

phi phenomenon

When we are watching a wild car chase scene in a movie we can be thankful for the:

inattentional blindness

You are sitting in an arena watching the end of a very close basketball game and you fail to notice that one of the referees has removed his shirt. This is an example of?

cornea

Before reaching the lens, light enters the eye through a transparent window at the front called the:

rods

Receptor cells that are more elongated.

cones

Receptor cells that dominate the fovea.

lateral geniculate nucleus

The main visual pathway that visual signals get processed in before being sent to the visual cortex.

superior colliculus

The secondary visual pathway that visual signals get processed in before being sent to the visual cortex.