TOPIC 5: SENSATION Flashcards Preview

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Flashcards in TOPIC 5: SENSATION Deck (94)
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1

sensation

encoding environment energy or chemicals in terms of neural signals.

2

Perception

organization and interpretation of neural signals.

3

Psychophysics

the study of relation between physical quantities and physiological experience.

4

Absolute threshold

weakest stimulus detected 50% of the time.

5

subliminal stimulation

hypnosis or hoax?
-- “subliminal” perceived up to 49% of the time.

-- what about stimuli never consciously perceived?

6

James Vicary (1957)

- reportedly showed 0.03 second messages repeatedly during a movie.

7

Murphy and Zajonc (1993)

will subliminal stimuli enter our awareness??
- presented Chinese characters preceded by subliminal faces.

- ratings of characters depended on facial expressions. (smiles=positive)

8

CBC show Close-Up to subliminal messages (1958)

- replicated study and no effect on behaviour .

9

difference threshold (just noticeable difference or JND)

smallest difference between two stimuli detected 50% of time.

10

JND increases as ..

JND increases as stimulus intensity increases.

11

Weber's Law (1834)

JND is a constant proportion of stimulus intensity.

12

scaling

how does our experience change as intensity changes?

example: are two identical light bulbs twice as bright as one?

13

Fechner's Law

sensory experience is proportional to the number of JNDs a stimulus is above threshold.

14

Fechners formula

S = k loge (I )  

S = sensory experience,
k = Weber fraction, 
I = stimulus intensity   

15

problems with Fechner's and Weber's law

- less accurate approaching absolute threshold

- less accurate with increase intensity

- observers response bias confound attempts to measure sensitivity, due to time of day, fatigue

16

Steven Power Law (1961)

uses magnitude estimation technique:

1) observer given standard stimulus, and certain value.

2) observer assigns values to other stimuli.

17

Steven Power Law Formula

S = aI^b

S = sensory experience
a = constant
I = stimulus intensity 
b = exponent

18

evolutionary adaptive significance

• pain quickly becomes very aversive (b>1)

• accurate estimation of length and distance (b=1)

• large range of light intensities can be perceived (b<1)

19

Signal Detection Theory

uses catch trials; no stimulus presented 50% of the time.

- determines observers response bias

- applies statistical methods to separate sensitivity from confounding factors

- does not determine a threshold

20

Vision

- Transduction of photons (light energy) to neutral impulses

21

Visible light

narrow slice of electromagnetic spectrum; exhibits properties of particle and wave characteristics .

22

Distal Stimulus

Object in the world

23

Proximal Stimulus

pattern of energy impinging on receptors

24

How does travel through the eye ?

cornea 
===> pupil (iris) 
===> crystalline lens
===> retina

25

Accommodation

lens changes its shape, which changes its focal length, keeping image focused on retina.

26

Receptors

rods and cones (contain photochemical)

27

Optic disk

hole where optic nerve exits; no receptors; BLIND SPOT

28

Fovea

for directed looking; contains only cones.

29

Sensory Adaption

experience of sensation changes with prolonged exposure.

30

Dark Adaption

rods lose sensitivity in bright light; regenerate bleached photopigment in - 20 mins.