Processing the Environment
•Depth, Form, Motion, Constancy
•Binocular Cues - retinal disparity (eyes are 2.5 inches apart). Convergence – things far
away, eyes are relaxed. Things close to us, eyes contract.
•Monocular Cues – relative size, interposition (overlap), relative height (things higher
are farther away), shading and contour, motion parallax (things farther away move
oConstancy – our perception of object doesn’t change even if it looks different on
retina. Ex. size constancy, shape constancy, color constancy.
•Hearing - inner ear muscle: higher noise = contract.
•Touch - temperature receptors desensitized
•Smell – desensitized to molecules
•Proprioception – mice raised upside down would accommodate over time, and flip it
•Sight – down (ex. Light adaptation, pupils constrict, rods and cones become
desensitized to light) and upregulation (dark adaptation, pupils dilate)
•2 vs. 2.05 lb weight feel the same.
•2 vs. 2.2 lb weight difference would be noticeable.
•The threshold at which you’re able to notice a change in any sensation is the just
noticeable difference (JND)
•So now take 5 lb weight, in this case if you replace by 5.2 weight, might not be
noticeable. But if you take a 5.5 lb it is noticeable.
•I = intensity of stimulus (2 or 5 lb), delta I = JND (0.2 or 0.5).
•Weber’s Law is delta I to intensity is constant, ex. .2/2 = .5/5 = .1.
oDelta I/I = k (Weber’s Law)
•If we take Weber’s Law and rearrange it, we can see that it predicts a linear
relationship between incremental threshold and background intensity.
oDelta I = Ik.
oIf you plot I against delta I it’s constant
Absolute threshold of sensation
•The minimum intensity of stimulus needed to detect a particular stimulus 50% of the
•At low levels of stimulus, some subjects can detect and some can’t. Also differences in
•Not the same as the difference threshold (JND) – that’s the smallest difference that
can be detected 50% of the time.
•Absolute threshold can be influenced by a # of factors, ex. Psychological states.
oExperience (how familiar you are with it)