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The biggest challenge of cognitive psychology
the mind is an unobservable black box, stimulus goes in, response comes out. all we can observe are reflections (output) of the mind: behavior, physiology
-one solution the problem -just look inside and see the contents of the mind-emphasis on analysis of consciousness into its constituent parts-inspired by chemistry (periodic table)
Problems with introspectionism
- 1. observations are difficult to verify-private events, not public-objective science requires that observations can be confirmed independently
- 2. you are observing the end products of processing, but not the processing itself-many processes are not accessible to conscious awareness
- -solution to the unobservable mind
- -psychology is the "science of behavior"
- -emphasized what can be DIRECTLY observed
- -rats in mazes
- -ignores the mind because it is unobservable
Problems with behaviorism
- 1. Cant account for the creativity and diversity of human behavior (ex: language)
- 2. Limiting science to obervable things is a bad idea
- -solution to the unobservable mind
- -INFER whats going on inside using experimental method
computational model of the mind
- -underlying assumption: the mind is somehow like a computer -get information from
- 1.sensory data,
- 2. mental representations
- a. procedural: knowing how
- b. declarative: knowing that
- -semantic: general knowledge
- -episodic: personal experience
- -processes: operators that transform info from one state to another (ex: word to image)
The stage model of cognition
stimulus-->info processing-->more process-->response -Each stage RECEIVES info, TRANSFORMS the info, and SENDS info to next stage
- Little Albert
- •We should look for the “causes” of
- behavior in the environment
- •Understanding behavior requires no
- reference to any unobservable event occurring within the individual
- •No fundamental differences between human
- and animal behavior
Pigeons playing pingpong
- •Rewarding successively closer
- approximations of a desired behavior
•Useful for teaching new behaviors
- -what you measure and analyze (the data)
- -reaction time-accuracy
- -brain activation
- what the experimenter manipulates
- -# of items to be memorized
- -amount of alcohol ingested
- -has LEVELS
- -an effect of an independent variable on the dependent variable
- -an effect of whats being manipulated on whats being measured
- -The effect of one independent variable DEPENDS on the level of a second independent variable
- -requires at least two ind. variables
- The study of the time course of mental processes
- -method: reaction time studies
- -what are the stages?
- -how long does each stage take?
- -Detection task: tap right finger when you see a red or green light
- -proposed stages: S-->detection-->response
- -Choice task: tap L finger for red, tap R finger for green
- -proposed stages: S-->detection->decision-->R
Donder's subtractive method
-subtract detective reaction time from choice reaction time to determine the time for the decision stage
Problems of Donder's subtraction method
- 1.assumption of pure insertion (-all stages remain the same when the new one is added-Problem: adding the decision stage may influence another stage (like detection)-leads to overestimate time )
- 2. assumption of additivity (-The durations of all stages add together to yield the reaction time (stages are serial)-Problem: stages might operate in parallel-leads to underestimate time )
- 3. Assumption that you already know that the stages are
- Memory studies, how long can we retain info. Forgetting Curve
- Used behaviorism to determine a property of the mind
- Cognitive Map
- Rat in the maze experiment
- the PROCESSES by which INFORMATION is TRANSFORMED into EXPERIENCES
- via the sense organs
- perception interpreted different ways
- cannot process into real world object
real world (tree)
image on retina
what we experience consciously
We are born as blank slates (tabula rasa). Thus, we must learn to sense and perceive.
(a.k.a. rationalist) Much of our knowledge is based on innately given characteristics. From this perspective, sensation and perception should be "hard-wired."
Lack of Correspondence
When percept does not correspond to distal stimulus. E.g., Perceptual illusions
When proximal stimulus does not correspond to distal stimulus, but the percept does.Our brains are correcting for missing or misleading information.E.g., Moving objects, moving eyes.
Our perception of an object's features remains constant even when viewpoint (and proximal stimulus) changes. Perception of size doesn't change with distance. Perception of shape doesn't change with viewing angle. Perception of darkness/color doesn't change with light
a door is a door is a door... whether it is open, shut or viewed at an angle
Environment provides all necessary cues.Our brains are pre-wired to pick up cues.Stimulus information is unambiguous
Perception uses data from the world and our prior knowledge and expectations.Sensory information is often ambiguous.Must rely on knowledge/expectations
Processing that is driven by the external stimulus, rather than internal knowledge. Direct perception claims perception is purely this
Processing that is driven by knowledge & expectationsConstructivism: uses both methods
Our knowledge can influence what we see
Monocular static depth cues
- -monocular cues: cues to distance that you only need ONE eye to take advantage of
- -static depth cues do not require you or the stimulus to be moving
- ex: linear perspective, texture gradient, relative size, shadows, motion parallax
Can depth perception cues explain the Muller-Lyer illusion
Corner, urbanization. further away, adjust for distance
The Ames room
- Is acutally trapezoid in shape -- When viewed with monocular vision through the small peep-hole, it appears as a normally rectangle room with the two back corners appearing the same distance away from the viewer- Physically equal sized objects in the two back corners appear at different sizes
Cliff Experiment. Depth perception innate?
•Patient SB, blind for whole life, but sight restored surgically.
•3-D cues in artwork are not perceived without experience (Hudson, 1960).
•People who live in dense jungle (studies by Turnbull, 1961).
- •Urban dwellers more likely to see certain visual illusions. (e.g., Muller-Lyer
Senses must convert physical stimulus.energy (e.g., chemical molecules) .into electrical changes in nerve receptor cells
The stimulus input must be processed and coded for intensity (i.e., strong smell vs. weak smell, bright vs. dim light, loud vs. soft sound) and qualitative aspects (e.g., red vs. blue, foul vs. pleasant, A flat vs. B sharp).Typically, much of this happens at post-receptor sites. Color coding begins at level of the receptors.
- Interactivity across Time.
- Interactivity across Space,
- Bottom up vs. top down
- ex. checker board shadow
Cells of the retina
- -light enters and passes the layers to the back of the eye
- -photoreceptor layer (rods/cones)
- -bipolar cell layer
- -ganglion cell layer-to brain
Rods and cones
- -photochemical reaction takes place inside the cell when exposed to light, wavelength
- -rods detect BRIGHTNESS
- -cones are concentrated at the fovea
- -blue, red, green cones
- -M and P cells pass to the lateral geniculate
- -Magnocellular and parvocellular
Differences Between Rods and Cones
- Rods--operate under low illumination and are achromatic -- night time receptors.
- allow us to see in dim light
- can not see fine spatial detail
- can not see different colors
- detect motion/peripheral vision
- Cones--operate under high illumination. Chromatic. Packed around fovea -- daytime receptors.
- allow us to see in bright light
- allow us to see fine spatial detail
- allow us to see different colors
- Potential must get above a threshold level for neuron to fire.
- Firing = generating an action potential
Action potential always has same strength. Either you get all of it (if above threshold) or none of it.
Once past threshold, active process (ion pumping) propagates action potential down axon
Short period after firing before neuron can fire again. Places upper limit on rate of neural firing. About 100 per second.
Receptive field for a particular ganglion cell is the portion of the visual field that causes some change in the firing rate.
- Firing Rate
- On-center (excitatory), off-surround (inhibitory)
- One important function is edge detection. Change in Illumination at the edge of an object.
transient, large response field, movement/location, dorsal stream
sustained response, small receptive field, patterns/colors, form, ventral stream
- part of the thalamus
- primary relay center for visual information received from the retina of the eye
Divides frontal, parietal, occipital, and temporal lobe
when activity in one region tends to inhibit responding in adjacent areas.Takes place at various levels of the visual system. If a ganglion cell is strongly activated, neighboring cells will be inhibited.
Repeated stimulation of a particular receptor leads to reduced responding.One example: Stabilized images on the retina fade away.
To account for phenomena like complementary afterimages, Herring proposed that we have two types of color opponent cellsred-green opponent cellsblue-yellow opponent cells
the trichromatic theory
- color vision arises from three kinds of cones
- Example: afterimages if we view colored stimuli for an extended period of time, we will see an afterimage in a complementary color.
Simple cortical cells
Bar of light,Specific orientation,Specific retinal position
Complex cortical cells
- very specific shapes, grandmother cells?
- This cell would become active every time a person thinks about a complex thing, such as his or her grandmother
pattern recognition theories
- -must explain how we recognize objects from many diff. viewpoints
- -Bottom-up theories: Template theory and feature theory
- -do NOT incorporate the influence of biases or expectations