Keywords Test1 Flashcards
Perception as an active process
We make unconscious inferences that are cognitively impenetrable based on sensory information
Perception as an unconscious inference
Interpret 3D pictures as 3D objects, process faces holistically
Inverse problem in perception
Perceived brightness and image can come from an infinite number of illumination combinations and shapes. The visual system must infer what it is
Cognitive impenetrability of perception
Cannot be penetrated by knowledge
Blind spot and filling in
No photoreceptors at the optic disk, there is a blind spot. Our brain fills in the gaps.
Various psychophysical methods
Method of adjustment
Observers adjust stimulus level until they response change from seen to not seen or vice versa
Method of limits
Gradually decrease/increase stimulus level until observers report change from seen to not seen or vice versa.
Method of constant stimuli
Show different stimulus levels in random order repeatedly; for each level tally number of “yes” responses
Threshold in psychometric curves
The curve starts at chance, the threshold is the steepest part of the curve, generally halfway between chance and 100 percent
Absolute vs relative thresholds
Absolute threshold
The minimum stimulus intensity that can be perceived
Relative threshold
The minimum difference between stimulus intensities that can be perceived
Weber vs Fechner laws
Weber = relative threshold is proportional to background level Fechner= two signals that are just noticeably different are separated by one unit of perceptual/internal response
Signal detection theory
Two factors that influence performance = signal and judgement.
d’
When the distributions are further away d prime is larger, more likely true positives
When the distributions are narrower d prime is larger to
When the distributions are entirely overlapping d prime is zero
D prime is a measure of sensitivity. Tells you how well hits can be distinguished from false alarms
D does not depend on criterion
false positive/negative
False positive -> test says yes when really no
False negative -> test says no when really yes
Characteristics of foveal vs peripheral vision
Fovea is clearer. Peripheral is mainly rods and is better in lower light.
Rods vs cones and their pathways
Rod: low light vision, no colour, low detail
Cone: Bright light vision, colour, high detail
Many rods to one ganglion, cones more one to one. Cone path is precise because info on which cone is activated is preserved. Rod cannot tell where photons come from because identical response for differing stimulations.
ON/OFF-center cells in retina/LGN
Gets excited if light is in the on region only, gets inhibited if light is in the off region only, if both lit then cancelation from lateral inhibition
Parvo vs magno cells/pathways
Parasol cells get inputs from many photoreceptors, poorer spatial resolution, respond faster to moving stimuli. Midget cells get inputs from fewer photoreceptors, higher spatial resolution but slower processing. More midget cells
Retinotopic map in V1
Ganglion cell axons from the retina preserve their order in LGN. Parvo (small) LGN cells get inputs from (small) midget ganglion cells. Magno (large) LGN cells get inputs from (large) parasol ganglion cells.
Cortical magnification in V1
Central 5° of visual field takes up 40% of V1
Columnar organisation in V1
cells sensitive to neighboring orientations are located next to each other. cells are organised systematically based on eye of origin.
First cell = -45 then the whole columns will be for aspects of -45
Simple cells in V1
Respond selectively to lines or bars in particular orientations with separate ON and OFF regions. They can be monocular or binocular. They are sensitive to length (bigger response with increasing line length up to a point)
Complex cells in V1
Like simple cells, complex cells are orientation selective and are sensitive to length. But they are mostly binocular and have no separate ON/OFF regions. They are sensitive to length (bigger response with increasing line length up to a point)
Hypercomplex cells in V1
Like complex cells except they obey end-stopping rule: increase response as line gets longer up to optimal length then decrease response if line gets longer still.
Ventral pathway goes to the temporal lobe, down from V1
Allows us to recognise shape, size, objects, faces, and words.
Terminates in medial temporal lobe, hippocampus, amygdala.
Contributes mostly to visual recognition, memory, emotion.
Dorsal pathway goes to the parietal lobe, up from V1
Handles aspects of the spatial layout such as location, distance, relative position, position in egocentric space, and motion.
Route feeds into motor cortex in frontal lobe.
Contributes mostly to visually-guided action and attention
