P/S: 86 Page Doc: Sensing the Environment

Question 1

visual cues

Answer 1

depth, form, motion, constancy

Question 2

binocular cues

Answer 2

(1) retinal disparity (eyes ~2.5 inches apart which allows
humans to get slightly different views of objects of world around. Gives humans an idea on depth.)

(2) convergence - Gives humans an idea of depth as well based on how much eyeballs are turned. Gives humans a sense of depth.
§ Things far away – muscles of eyes relaxed.
§ Things close to us – muscles of eyes contract.

Question 3

retinal disparity

Answer 3

binocular cue

depth - eyes are 2.5 in apart and have different view of the world

Question 4

convergence

Answer 4

binocular cue

depth

far away - muscles of eyes relaxed, close up - muscles of eyes contract

Question 5

monocular cues

Answer 5

form of an object

relative size - Can infer with one eye. The closer an object it is perceived as being bigger. Gives us an idea of form

Interposition (overlap)- Perception that one object is in front of another. An object that is in the front is closer.

Relative height- things higher are perceived to be farther away than those that are lower.

Shading and contour- using light and shadows to perceive form depth/contours – crater/mountain.

motion parallax - “relative motion” Things farther away move slower,
closer moves faster.

constancy - Our perception of object doesn’t change even if the image cast on the retina is different.

Question 6

constancy

Answer 6

monocular cue

Our perception of object doesn’t change even if the image cast on the retina is different. Different types of constancy include size constancy, shape constancy, color constancy.

• Size Constancy: One that appears larger because it’s closer, we still think it is the same size.
• Shape Constancy: a changing shape still maintains the same shape perception.

Color Constancy: despite changes in lighting which change the image color falling on our retina, we understand (perceive) that the object is the same color.

Question 7

sensory adaptation: hearing

Answer 7

higher noise = muscle contract (this dampens vibrations in inner ear, protects ear drum.) Takes a few seconds to kick in! So does not work for immediate noises like a gun shot, but it works for being at a rock concert for an entire afternoon

Question 8

sensory adaptation: light

Answer 8

down regulation or up regulation to light intensity.

Down regulation: light adaptation. When it is bright out, pupils constrict (less light enters back of eye), and the desensitization of rods and cones become desensitized to light)

Up regulation: dark regulation. Pupils dilate-, rods and cones start synthesizing light sensitive molecules

Question 9

Weber’s law

Answer 9

predicts the JND in stimulus intensity is a fixed proportion of the current stimulus magnitude.

delta I/I = k
I = absolute magnitude of stimulus
delta I = difference in stimulus required to be perceived (JND)
k is a constant

……

ΔI (JND)/I (initial intensity) = k (constant)

o ex. 0.2/2 = 0.5/5 = 0.1, change must be 0.1 of initial intensity to be noticeable

• If we take Weber’s Law and rearrange it, we can see that it predicts a linear relationship
between incremental threshold and background intensity.
o ΔI=Ik.
o If you plot I against ΔI it’s constant

Question 10

JND

Answer 10

amount the stimulus intensity must change before the difference in intensity is noticeable 50% of the time

Ex. a lightbulb may need to bright or dim by 10% before you are able to notice a change in brightness

Question 11

is JND fixed?

Answer 11

No: signal detection theory and JND… JND is not fixed but depends on perceptual and motivational factors

increased motivation to notice a stimulus may decrease JND

Question 12

how does increased motivation affect JND?

Answer 12

decrease

Question 13

Weber’s Law and stimulus intensities

Answer 13

will not hold at extremely high or low intensities because of physical constraints of sensory receptors

Question 14

absolute threshold of sensation

Answer 14

The minimum intensity of stimulus needed to detect a particular stimulus 50% of the time.

Question 15

absolute threshold of sensation vs JND

Answer 15

The minimum intensity of stimulus needed to detect a particular stimulus 50% of the time.

VS

ND: that’s the smallest difference that can be detected 50% of the time. Related but different concepts.

Question 16

factors influencing absolute threshold

Answer 16

expectations
experience
motivation
alertness

Question 17

subliminal stimuli

Answer 17

below the absolute threshold of sensation

Question 18

Timing: Neuron encodes 3 ways for timing

Answer 18

Non-adapting- neuron consistency fires at a constant rate

o Slow-adapting - neuron fires in beginning of stimulus and calms down after a
while

o Fast-adapting - neuron fires as soon as stimulus start…then stops firing. Starts
again when stim stops).
— pain and

Question 19

bottom up processing

Answer 19

Begins with stimulus. Stimulus influences what we perceive (our perception).
o No preconceived cognitive constructs of the stimulus (never seen it before)
o Data driven. And the stimulus directs cognitive awareness of what you’re looking
at (object)
o Inductive Reasoning. Always correct.

Question 20

top down processing

Answer 20

uses background knowledge influences perception. Ex. Where’s waldo
o Theory driven. Perception influenced by our expectation
o Deductive Reasoning
o ex. creating a cube when it’s not there! Not always correct.