Stimulus identification & processing information (s1w2)

Question 1

factors affecting stimulus identification

Answer 1

• Clarity
• Intensity
• Modality (type of stimulus e.g. visual, auditory, tactile)

Question 2

stimulus intensity - startle reflex

Answer 2

• reaction time is shorter when the stimulus is intense
• when startled we by-pass some of the processes and it triggers the reaction that was waiting to be done
• reduces simple reaction time by 56 ms

Question 3

reaction time and modality

reaction time for visual stimuli

Answer 3

• 100 - 180 ms
• big range - we don’t process all visual info in the same way

Question 4

reaction time and modality

reaction time for auditory stimuli

Answer 4

85 - 100 ms

Question 5

reaction time and modality

reaction time for tactile stimuli

Answer 5

120 - 150 ms

Question 6

sources of sensory information

exteroception

Answer 6

• from outside the body
• vision
• audition (hearing)

Question 7

sources of sensory information

interception

Answer 7

• from within the body

Question 8

sources of sensory information

proprioception

Answer 8

• sensory organs giving info on orientation and movement
• muscle spindle - gives info about muscles changing length
• Golgi tendon organ - gives info about tension in muscles
• vestibular apparatus - in inner ear, gives info about linear and angular acceleration of the head
• joint receptors - only normally give info at the extremes of the joints range of motion
• cutaneous receptors - in the skin, give info about things like pressure, heat, pain

Question 9

rods and cones

Answer 9

• rods detect light (very sensitive) but don’t see in high resolution (used more in the dark)
• cones help us see in HD and detect colour
• 90 million rods and 4.5 million cones
• high concentration of cones in the fovea

Question 10

the visual field

Answer 10

• what we see is what our brain has interpreted
• light reflects into the eye and is flipped at the lens, so it lands upside down on the retina
• quality of vision drops by 75% if you go outside of 6° of your visual field
• to see in great detail, you need to move your head/eyes

Question 11

binocular vision

Answer 11

• we combine info from both eyes to give binocular vision
• only in regions where the field of view of both eyes overlap
• between 160 - 180°
• light falling onto the eye is sent to different parts of the brain
• e.g. info from the temporal hemiretina and nasal hemiretina gets combined and sent to occipital lobe

Question 12

what are the two visual streams called?

Answer 12

• ventral stream
• dorsal stream

Question 13

ventral stream

Answer 13

• processes info ab out what it is we’re looking at (identification)
• from occipital lobe, info goes to temporal lobe

Question 14

dorsal stream

Answer 14

• processes info about where things are and how things are moving
• from the occipital lobe, info goes to the parietal lobe

Question 15

focal vision (ventral)

Answer 15

• used in identification
• uses the central portion of our visual field
• slightly longer reaction times because brain consciously involved - reaction time takes longer because we need to use long term memory to make identification

Question 16

ambient vision (dorsal)

Answer 16

• Info form the optical flow
• uses central and peripheral visual field
• non-conscious - quicker reaction time because we don’t need to use long term memory

Question 17

visual illusions

Answer 17

• Fools the focal visual stream
• When we interpret what the picture is, we can get misinformation
• Can’t fool the ambient visual stream

Question 18

optical flow

Answer 18

• As we move forwards, the patterns of light move across the retina (optical flow)
• If an object is coming towards us, change in pattern of light at the back of the eye
• Gives us info about time to contact

Question 19

time to contact (tau τ) equation

Answer 19

T_contact ≈ size of image / rate of expansion

Question 20

time to contact example

Answer 20

e.g. ski jumping - need to know when they will land so they can land safely

Question 21

head movements of a skier with a head cam

Answer 21

• Skier never looked at the sky when rotating
• Landing areas is always in field of view (through 3 somersaults and 5 twists)
• Not using focal visual stream but is aware of where the landing area is, and when he’s likely to contact it

Question 22

head movements - long jump approach (Scott et al, 1997)

background

Answer 22

• Moving observer
• Approximately 35 - 40 m run up
• Over 20 strides
• 0.20 m width board
• How is the approach regulated?
• Is this learned? Is this an expert strategy?
• Measure where the foot is placed and calculate SD

Question 23

head movements - long jump approach (Scott et al, 1997)

results and conclusions

Answer 23

Results

• All have increasing variability - not putting feet in exactly the same place, until about 5 strides out, then they hone in on the take off board
• Adjust foot placements to ensure we’re as consistent as possible for the take off
• Novices also followed the same pattern

Conclusion

• Descending trend is a fundamental strategy, but training can improve it
• Non-long jumpers use visual info to regulate their approach