Stimulus identification & processing information (s1w2) Flashcards
factors affecting stimulus identification
- Clarity
- Intensity
- Modality (type of stimulus e.g. visual, auditory, tactile)
stimulus intensity - startle reflex
- 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
reaction time and modality
reaction time for visual stimuli
- 100 - 180 ms
- big range - we don’t process all visual info in the same way
reaction time and modality
reaction time for auditory stimuli
85 - 100 ms
reaction time and modality
reaction time for tactile stimuli
120 - 150 ms
sources of sensory information
exteroception
- from outside the body
- vision
- audition (hearing)
sources of sensory information
interception
- from within the body
sources of sensory information
proprioception
- 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
rods and cones
- 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
the visual field
- 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
binocular vision
- 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
what are the two visual streams called?
- ventral stream
- dorsal stream
ventral stream
- processes info ab out what it is we’re looking at (identification)
- from occipital lobe, info goes to temporal lobe
dorsal stream
- processes info about where things are and how things are moving
- from the occipital lobe, info goes to the parietal lobe
focal vision (ventral)
- 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
ambient vision (dorsal)
- 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
visual illusions
- Fools the focal visual stream
- When we interpret what the picture is, we can get misinformation
- Can’t fool the ambient visual stream
optical flow
- 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
time to contact (tau τ) equation
Tcontact ≈ size of image / rate of expansion
time to contact example
e.g. ski jumping - need to know when they will land so they can land safely
head movements of a skier with a head cam
- 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
head movements - long jump approach (Scott et al, 1997)
background
- 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
head movements - long jump approach (Scott et al, 1997)
results and conclusions
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
