Perception

Question 1

Sensation

Answer 1

Passive process of bringing information from the outside world into the body and brain

Question 2

Perception

Answer 2

Active process of selecting, organising, and interpreting info brought to brain by the senses

Question 3

Transduction

Answer 3

Conversion of physical stimulus into electrical signals

Taste/ smell = chemoreception
Touch/ sound = mechanoreception
Sight = photoreception

Question 4

Hearing (audition)

Answer 4

Sound = pressure changes in the air

How many waves per second determines frequency of the sound

30Hz - 20,000Hz

Sound waves funnelled along ear canal —> ear drum —> cochlea

Hair cells along basilar membrane pick up vibration- different frequencies = vibrate at different points

Question 5

Sight (vision)

Answer 5

Light enters through the pupil

Focussed onto retina

Retina covered in photoreceptor cells:

• rods- 125 million- dim light
• cones- 6 million- bright light- colour
• fovea- detailed vision- only cones

Question 6

Touch (somatosensation)

Answer 6

Receptors within skin responds to pressure and movement

Different receptor cells respond to different types of stimulation

Sensitivity varies across body parts with density of mechanoreceptors- two-point discrimination technique

Question 7

Taste (gustation)

Answer 7

10,000 taste buds on tongue

5 types: sweet, sour, salty, bitter, umami (savoury)

Continually destroyed and replaced

Question 8

Smell (olfaction)

Answer 8

Cells in nasal cavity (epithelium) respond directly to chemical compound

1000 types of receptor molecules in olfactory receptor cells

Not sent to thalamus—> directly to brain

Question 9

Gestalt laws

Answer 9

“Organised whole”- how parts are arranged into forms and perceived as whole

Proximity- close together= belonging together
Similarity- look similar= part of same form
Continuation- perceive lines following smooth course
Closure- boundary isn’t to perceive form, small elements arranged in groups= larger figures, see illusionary lines
Pragnaz- organise scene by simplest explanation
Common fate- move in same way= group
Symmetry- symmetrical= grouped together
Parallelism- parallel= grouped together

Question 10

Feature representation

Answer 10

Record from a single neuron, present visual stimuli, check which elicit a response

Optic nerve:

• centre surrounding organisation
• light centre and dark surround
• responsive to dot-like circular visual stimuli

Question 11

Feature representation

HUBEL AND WIESEL

Answer 11

Measure response lines in different places, at different orientations in cortex

Neural encoding= firing rate

Highest firing rate= greatest sensitivity

Receptive field gets larger as one ascend hierarchy- more complex

Question 12

Top-down vs bottom-up

Answer 12

Top-down:

• background knowledge and expectations influence what is being perceived
• knowledge driven
• context changes perception
• environment gives clues when ambiguous

Bottom-up:

• processing the stimuli influences what is being perceived
• data driven

Question 13

Feature representation

Resolving ambiguities

Answer 13

Decide which visual scene caused the image on the retina

Cues:
-features of the image give clues to the nature of the stimulus

Assumptions:
-expectations about what we will see or what different cues mean

Question 14

Streams of visual perception

UNGERLEIDER & MISHKIN

Answer 14

Ventral stream:

• what pathway
• shape, objects
• ventral, to inferior temporal lobe

Dorsal stream:

• where pathway
• motion
• dorsal, to superior parietal lobe