Lec 4-2 Flashcards
describe the size contrast illusion (Ebbinghaus illusion) describe a study done and its findings
perceived side of central circle is affected by surrounding circles
if circle is surrounded by larger circles it appears smaller and vice versa.
Study done:
- people asked to estimate grip aperture needed to pick up a disk then asked to go pick the disk up
- results found that conscious estimation of disk size and motor control when going to pick up disk were different
- your conscious thought was fooled by the illusion but you motor system wasn’t
Describe flanker illusion and how to calculate
shows two sets of rectangles, size of rectangle next to reference rectangle influences the perception of its size
to calculate effect, subtract grip aperture when estimating by aperture when reaching e.g. if your grip aperture reached 6cm on estimation but the reaching aperture was 4cm, then effect was 2cm.
VERIFY
In reaching experiment with flanker illusion, describe protocol and what it shows including what parts of brain are used in each protocol
Participants asked to prepare to reach for rectangular tiles, there will be a rectangle of different size next to target tile.
Vision trial - participants prepare for their movement then are given an audio cue to reach for the tile and could see up until they started moving.
Occlusion trial - when cue to move comes, vision is occluded immediately (before they had time to react and start movement, and they have to reach without seeing. Must use immediate memory.
They also did delayed trials where they set up then vision is occluded until cue, then for vision trial, they get vision until movement starts, and for occlusion trial, they get no vision back.
Vision trial uses the dorsal stream because the dorsal system guides motor actions and spatial location, Occlusion trials use the ventral system because it is for object recognition and shape identification
Vision trials were not as affected by the illusion as the occlusion trials because they use these different systems.
are there instances where reliance on instant memory in reaching tasks can be better for people with vision problems over controls?
Yes. Experiment with pantomimed grasping trials and actual grasping trials. Patient with optic ataxia (problem with dorsal stream - using vision to guide motion) perform better with pantomimed grasping trials (where they remove the target before you start grasping) because they don’t need to rely on dorsal stream and can rely on ventral stream.
CLARIFY - are they better than control groups?
