Sensation and perception

Absolute Threshold: Smallest amount of stimulation needed for detection by a sense.
Signal Detection Theory: Explains how one responds to stimuli; can be aware or unaware of a signal. Possible outcomes:
- Hit: Signal present and correctly detected.
- Miss: Signal present but not detected.
- False Alarm: Signal not present but wrongly identified.
- Correct Rejection: No signal present and correctly identified.
Bias:
- Liberal: More likely to say “yes, the signal is present.”
- Conservative: More likely to say “no, signal absent.”

Visual Information: Affected by stimuli in the environment (e.g. driving experience, airport security).
Feature Search: Looking for a single feature among distractions.
Conjunctive Search: Combination of multiple features, longer search time with many stimuli.

Originally studied psychic abilities; revealed that sensory receptors are more sensitive to change.
In constant visual fields, perception eventually fades (e.g. constant red fading to grey).

Light Pathway:
1. Light enters through the cornea.
2. Regulated by the pupil.
3. Focused by the lens onto the retina.
Photoreceptors:
- Rods: Sensitive to light and dark.
- Cones: Sensitive to color and fine detail.
- Ganglion Cells: Sensitive to blue wavelengths.
Distribution: Cones in the fovea (center); rods in the periphery.

Pathway from Eye to Visual Cortex:
1. Light through cornea -> pupil -> lens -> retina.
2. Electrical signals sent down optic nerve.
3. Pass through thalamus to primary visual cortex for initial processing.
What and Where Pathways:
- What Pathway (Ventral Stream): From occipital to temporal lobe; involved in object recognition. Damage can cause:
  - Apperceptive Visual Agnosia: Impaired object recognition, object seen as parts.
  - Associative Visual Agnosia: Can see shape but cannot identify it.
- Where Pathway (Dorsal Stream): From occipital to parietal lobe; guides movement based on object location. Damage can cause:
  - Optic Ataxia: Difficulty using spatial information for movement.
  - Hemispatial Neglect: Unawareness of one side of space.
  - Akinetopsia: Inability to perceive motion.
  - Apraxia: Difficulty with voluntary movement.

Theories of Color Vision:
1. Trichromatic Theory: Three cones responsive to red, green, blue.
2. Opponent-Process Theory: Pairs of colors processed by retinal ganglion cells (e.g. red-green).
Color Blindness Types:
- Anomalous Trichromat: Reduced sensitivity to one color.
- Dichromat: No sensitivity to one color.
- Monochromat (Achromatopsia): See in greyscale.
- Cerebral Achromatopsia: Brain processing impaired, not eye problem.

Perceptual Set: Cognitive bias affecting interpretation based on past experiences.
Inattentional Blindness: Failure to notice unexpected stimuli when attention is focused on another task.
Bottom-Up vs Top-Down Processing:
- Bottom-Up: Based on sensory data into perceptual experience.
- Top-Down: Utilizes prior knowledge to make sense of new information.

Navon Task: Demonstrates importance of global and local features in visual perception.
Feature Integration Theory:
1. Tiers:
- Preattentive Stage: Automatic feature detection (color, shape).
- Focused Attention Stage: Requires attention to combine features.
Feature Cells: Respond to specific visual stimuli, initially identified in studies with cats.

Faces processed differently; specialized cells in visual cortex.
Prosopagnosia: Impairment in face recognition due to brain damage.
Sound Localization:
- Lateral Cues: Determine sound direction using both ears.
- Median Cues: Identify elevation (above, below).