Lecture 5 Notes
Sensation and Perception
Perception:The selection, organization, and interpretation of sensory input.
Perception Is Active
o Defined in terms of probability of responding
Absolute Threshold: the intensity level at which the probability of detection
is 50%. “Truly” absolute threshold incorporates a probability of detecting a
stimulus at threshold intensity would jump from 0% to 100% immediately.
o JND (Weber’s Law)
o Psychophysical Scaling (Fechner’s Law): if you open a sixty watt light in a pitch black
room. And then if you turn on a second 60 watt light, the difference is minimal. But
when you put the third 60-watt light, the difference is even more minimal. Constant
increments in the alteration of something produce minimal sensory recognitions.
REVIEW FECHNER’S LAW
- Signal Detection Theory:
The four outcomes that is possible in attempting to detect the
presence of weak signals:
Perception without Awareness
- Subliminal Perception
- Noise from ventilation, become unnoticeable because we
adapt to it.
- Visual System
Stimulus: Light (Amplitude and wavelength) visible spectrum and neural impulses. We don’t see
everything exactly the way it is. We actively reconstruct what we see. For example, the images in the
back of our eye is up-side-down however, our brain flips the image to show the normal image.
Saccades: Our eye is ALWAYS moving minimally to prevent images from fading away (like the adaptation
we have to wearing a hat)
Retina to optic disk/optic nerve/ optic chiasm to two divergent pathways
- To the superior colliculus (I midbrain involves coordination with other sensory input).
- (main pathway) to the thalamus to lateral geniculate nucleus (LGN( in occipital lobe to
primary visual cortex secondary visual cortex to temporal and parietal lobes. (Lots of higher
Dorsal Stream (The Where)
Ventral Stream (The What)
Information processing in the visual cortex:
- Simple cells
- Complex cells
- Feature detectors
- Face detectors
Features then seem to get “assembled” Colour
- Subtractive colour mixing: a bright yellow ball bucket