● Feature-detector story (two girls, 1 cup): Black background with white features or white
background and black features
● Distal stimulus (thing in world) → reflected light → proximal stimulus (retinal image)
● Retinal Image: stimulation of receptors produces sensations of brightness and colors.
Then light sensations must be interpreted as objects.
- Perception is knowledge of world (experience of objects and events) based on
sensations. Sensations come from the retinal image.
- You’re seeing wavelengths, colors (stimulus) which are projected onto the retina in the
back of the eye which signals neurons to fire.
- Need to be able to interpret a pattern of activity (recognizing a chair)
● Proximal stimulus (retinal) image is inadequate for knowing about distal stimulus. Three
problems with the proximal image:
1. Inverted: Image of object is upside down on retina.
2. Ambiguous: Size and distance trade off (close up small object has same image as far off
3. Two-dimensional: The image is flattened and then curved, but objects are three
- Basically, perception doesn’t happen in the eye, it happens in the brain.
● Hermann von Helmholtz (trichromatic theory)(measures speed of nerve impulse): Start
with retinal image, but it is not accurate view of the world. However, there are cues
(depth) that go along with an image. Add knowledge/inferences of structure