2 - Sensation vs Perception

Question 1

Sensation

Answer 1

• trigger electric signals in nervous system
• stimuli hits receptors & causes neural firing
• energetic/vibration (ex) signals from env turned into electrical signals
• transduction

Question 2

Perception

Answer 2

• Sensory processing

- Info enters brain & brain creates meaning

Question 3

Sensory receptors

Answer 3

Photoreceptors- respond to EM / visible light; sight
Hair cells- movement of fluid in inner ear- hearing; balance; rotational and linear acceleration

Nociceptors- pain/noxious stimuli- somatosensation

Thermoreceptors- change in temp- somatosensation

Osmoreceptors- Osm of blood - water homeostasis; hypothalamus; ADH from posterior pituitary

Olfactory receptors- volatile compounds/smell, chemoreceptors

Taste receptor- dissolved compounds; chemoreceptors

Question 4

Absolute Threshold

Answer 4

Absolute threshold - minimum stimulus from environment that triggers receptors 50% of the time (minimum strength of stimulus you can sense 50% of time)- sensory
-abs thresh - vision: candle 30 miles away, hearing: watch 20 ft away- expt’ally determined
-limits of perception; constant bombardment of stimuli; either signal is too low intensity or outside the spectrum of perception
ex) we see 400 (purple) - 700 (red) nm
snakes can see IR; reindeer- UV; lichens (eat)
ex) butterflies- widest range visual spectrum

Even stimuli that trigger receptor don’t have to be perceived by brain— threshold of conscious perception
EXPT- words flash fast, msg to brain but brain doesn’t read it, then show pic of person and ask what mood they are- word affects mood perceived
orrrr self-referential word “me” “I”- see mirror; less likely to shoplift/immoral

Flash “bread” then “butter” and “bottle”- brain prime to detect butter (related to bread) faster

Abs threshold = subliminal messages / limina- msgs given that don’t enter consciousnesness
-briefly affect mood/priming; canNOT change behavior

Question 5

Difference Threshold

Answer 5

• How can you detect change (which red is brighter, which sound is higher pitched)
• If you hold 2 objects, how can you tell which one is heavier

Just noticeable difference- the difference in pitch/wavelength etc that you can tell that they’re different sounds/etc 50% of time

Weber’s Law-
At 400 Hz, 3 Hz JND
At 1000 Hz…. 4/400 = x/1000; x = 7.5 Hz

Question 6

Signal Detection Theory

Answer 6

Perceiving important signals, ignoring useless ones
ex) hearing your name in a loud party; air traffic controller- is there danger

Nonsensory factors in perception- based on experiences, motives, expectations
-Basically if you’re expecting stimulus, if it’s important, if you are alert/ready to receive signals, and if it matches your experience

Important = food, avoid predator/toxin, mate/pheromones

Hearing test- finding absolute thresholds in frequency & intensity

Question 7

Response bias

Answer 7

• you respond to a signal not because you detected it, but b/c you’re being studied
• Demand characteristic- participants subconsciously change response b/c being studied based on what the think the expt purpose is

Question 8

Signal detection expt

Answer 8

Catch trials & noise trials

Subject response(SR):
Yes / No

Signal present: SR: Y = Hit; SR: N = Miss
Signal absent: SR: Y = False alarm; SR: N = Correct negative

Signal detection theory- sensation/perception based on internal/external factors like introversion/background noise

Question 9

Sound

Answer 9

Loudness = intensity
Frequency = pitch

Question 10

Adaptation

Answer 10

Physiological (sensory) components - ex) pupil dilation in low light

• changes amnt of stimulus brain receives
• step in cold; pool- receptors tired of signaling, stop- reduce temp set point- if you go into warmer water, body will say it’s hot

Psychological (perceptual) components- if you can divert your attention to it and suddenly it’s there- that’s psychological- paying attention to feeling of socks on feet, feeling of sitting, bg noise

If you stare at something for a long time, why doesn’t it disappear- physiological

• your eyes are moving around all the time (micro movements) so photoreceptors don’t always see same image
• expt- special goggles- keep image on photoreceptors/retina constant- words/faces begin looking funky/hard to read

After-image effect- look at light for long time and look away, eyes get tired
-look at blue for a long time, look away, see yellow

Brain registers things that change/new or things you put attention on / important things

Question 11

Physiological zero

Answer 11

the temperature at which an object in contact with the skin feels neither warm nor cold
-pool felt cold, then normal

Question 12

Demand Characteristic

Answer 12

-Demand characteristic- participants subconsciously change response b/c being studied based on what the think the expt purpose is

Response bias - b/c being studied