Exam 3 - PSYCH 100 UIUC

Inattentional Blindness

Failure to detect stimuli that are in plain sight when our attention is focused elswhere.

Selective attention

Allows us to focus on a subset of sensory input while "turning down" everything else.

Transduction

Process of converting external stimuli into neural stimuli.

Sense Receptor

Specialized cell for a sense:

- Ex: Rods & Cones convert light into neuronal signal

Sensory Adaptation

Activation is greatest when a stimulus is first detected.

Absolute Threshold

Lowest level of a stimulus that we can detect on 50% of trials.

Sight - Seeing a candle from 30 miles away on a clear night.

Hearing - Hearing a watch tick 20 feet away

Touch - Feeling a bees wing fall onto your cheeck from 1 cm away.

Smell - Smelling one drop of perfume in a 6 room house.

Taste - Tasting 1 tsp. of sugar dissolved in 2 gallons of water.

Just Noticeable Difference (JND)

Smallest change in a stimulus that we can detect.

Weber's Law

Constant proportional relationship between the JND & The Stimulus. (No candles lit, easy to tell when one more is lit. Many candles lit, hard to tell when one more is lit.)

Signal Detection Theory

Looks at how stimuli are detected under different conditions.

Goal: Separate people's accuracy from their bias to say yes.

Signal to Noise ratio: Harder to detect a signal when background noise increased.

Subliminal Processing

Processing of sensory info that occurs below the level of conscious awareness.

- Small, short term effects.... NOT LONG TERM

- No in-depth processing of meaning.

Parallel Processing

Lots of info from lots of senses coming in at once.

Top-down Processing:

Beliefs and Expectations are imposed on raw stimuli we perceive.

-Take meaning & use it to understand stimulus.

Bottom-up processing

Construct a whole stimulus from its parts, start from raw stimulus & construct meaning.

Top-down influences:

- Sensory input is ambiguous, often incomplete.

-When determining object identity, context can set up expectations & help generate plausible hypothesis.

The Eye:

Sclera - White of the eye

Iris - Colored part of the eye: 2 different pigments.

Pupil - Hole where light enters - Smaller to let less light in.

-Dilate w/ complex things & when you see attractive ppl/ppl you love.

Cornea - Bends incoming light

Lens - Bends incoming light

-Accomadation: Muscle reshapes lens to focus

Retina - Photoreceptors do transduction

-Rods: Light/Dark ; movement, plentiful

-Cones: COLOR; near fovea; need lots of light; fine details, less numerous

Fovea - Central Part of retina ; Sharpness of vision.

Optic Nerve - Axons of ganglion cells

Blindspot: No rods or cones b/c axons leaving the eye.

Trichromatic Theory

3 kinds of cones; each sensitive to different colors.

Color Blindness: Can't see all colors

-Deficiency in amount of one type of cone

- Usually dichromates: Red-green dichromates = can't distinguish red walls. (Dogs are dichromates, see just like red-green dichromates).

Opponent- Process Theory

Pairs of "opponents"

-Red vs. Green , Blue vs. Yellow , White

-Red inhibits green

-Evidence for equal after image.

Visual Pathway

1. Optic Nerve

2. Optic Chiasm

- Crossover

- left visual field to right brain, right visual field to left brain.

3. Thalamus - Sensory Relay Point

4. Occipital Lobe (V1)

Visual Perception

Motion Detection: To determine motion, brain compares visual frames of what is to what was.

Phi-phenomenom: Perceiving flashing lights as movement; principle behind movies and animation.

- A lack of this is called "motion blindness"

Gestalt Principles

Proximity = Group things that are close together

Similarity = Group similar things together

Continuity = Objects along a continuous line are one object

Closure = Assume shapes are closed & "fill in" missing information.

Symmetry = Group things that are symmetrical

Figure-ground = Immediately focus on a central figure & ignore background (Hour glass vs. peoples face's).

Constancy

- We impose beliefs about constancy on our perception.

- Objects appear the same despite dangers in retinal (shape, size, & color)

Shape Constancy:

Perceive same shape even if shape changes retina.

- Textbook looks like a rectrangle no matter how you move it.

Color constancy

We perceive stimuli as consistent across varied conditions.

-Colors should stay constant when moving from high brightness to low.

Size constancy

Our brain assumes that similar objects are actually similar sizes.