Cog Psych Exam 1
• Black box—the mind is unobservable
• Introspectionism—solution to the black box, look inside to see what’s going on (Wundt,
Difficult to verify.
Private events, not public.
End product of cognitive processing, not the process itself.
• Behaviorism—solution to the black box, emphasis on what can be directly observed
Can’t account for diversity of human behavior
• Example: language.
Limiting science to the observable is a bad idea
• Who’s ever seen an electron?
• Shaping—rewarding successively closer approximations to a desired behavior
• Cognitive approach—solution to the black box, infer what is going on inside brain
• Main effect--An independent variable has an effect on a dependent variable. Can be two
independent variables working on two different dependent variables.
• Donders—Mental chronometry: The study of the time course of mental processes.
• Subtractive Method--the difference between detection and the total time will give us the
Assumption of Pure Insertion
• All stages remain the same when the new one is added • Problem: adding the decision stage may influence another stage
Assumption of additivity.
• The durations of all stages add together to yield the reaction time.
• Problem: Stages might operate in parallel.
Assumes you already know what the stages are.
• Problem: You probably don’t
• Little Albert experiment showed evidence of classical conditioning in Humans
• Perception--The means by which information acquired from the environment is
transformed into experiences of objects, events, sounds, tastes
• Ambiguous figures-- More than one possibility for a figure, toggle back and forth
• Illusionary contour -- See a figure that isn’t there
• Impossible figure-- The clues are contradictory
o Much of our knowledge is based on innately given characteristics. From this
perspective, sensation and perception should be “hard-wired.”
o We are born as blank slates (tabula rasa). Thus, we must learn to sense and
• Nature (genes) vs. Nurture (environment)
• Stages of perception
o It is always indirect
o Distal stimulus
o Proximal stimulus
Some energy bounces off the tree and reaches our eyes
o Percept Lots of processing of that proximal stimulus in our brains to get to the final
percept: what we experience when we look at the tree
o Lack of correspondence
When a percept doesn’t correspond to the distal stimulus
o Paradoxical correspondence
Proximal stimulus doesn’t correspond to distal, but the percept does
Our brains correct the information
Example: perceptual constancy
• 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.
• Checker shadow illusion
o So maybe our visual system just measures how much light
is bouncing off (reflected) an object: More = lighter shade,
less = darker shade.
o But this wouldn’t work very well. Because of changes in
Depth perception is an example
• Distal stimulus (the world) is 3D
• Proximal stimulus (on retina) is 2D
• Perceptual experience is 3D
• Example of paradoxical correspondence
• Monocular Cue: Information available to one eye.
• Binocular Cue: compare image received by both eyes.
• Bottom up vs. Top down
o Bottom up Processing that is driven by the external stimulus, rather than internal
Direct perception claims perception is purely bottom-up
o Top down
Processing that is driven by knowledge & expectations
Constructivism: Bottom-up and top-down processes
o Direct perception
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
Sensory information is often ambiguous.
Must rely on knowledge/expectations
• Is depth perception innate?
o 6 month olds avoid “cliff”
o Species like lambs, cats, rats, that walk on 1st day after birth avoid cliff.
o 2 month olds heart rate goes down on cliff side. They notice depth but are not
• Common to all sensory/perceptual systems
o Transduction: from physical to neural
Get from something in the environment to action potentials
Senses must convert physical stimulus energy into electrical changes in
nerve receptor cells
• Visual receptor cells: Rods and Cones
o They respond to certain wavelengths of lights o Neural Coding
Code for things like pitch or loudness, color or brightness
Both qualitative and quantitative
Interactivity across time
• What we perceive right now vs. past or future
Interactivity across space
• Perception is affected by what’s around it: visual context
Bottom up vs. top down
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).
Most of this coding takes place post-receptor
Color coding happens at receptors
Neurons fire action potential
• Rate of firing
• Number of neurons firing
• Which neurons are firing
In time: Color Adaptation
• Affected by what comes before it and sometimes immediately after
In space: contrast effects
• Structure of the Visual System
o Overview – Primary visual pathway.
The eye - Retina, photoreceptors, ganglion cells
The thalamus Primary visual cortex
Two visual pathways: “What” vs. “Where”
• Dorsal stream—the where
• Ventral stream—the what
o Distal Stimulus
Light is emitted from a light source and the light hits some distal stimulus
(a tree, a car, your BFF).
Some frequencies of light are absorbed by the distal stimulus. Other
frequencies of light are reflected off the distal stimulus.
Some of this reflected light reaches your eyes.
Creates proximal stimulus on retina
• Functional differences between rods and cones
allow us to see in bright light
allow us to see fine spatial detail
allow us to see different colors
allow us to see in dim light
can not see fine spatial detail
can not see different colors
detect motion/peripheral vision
• Neural Firing
Potential must get above a threshold level for neuron to fire.
Firing = generating an action potential
o All-or-none: 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
o Refractory period:
Short period after firing before neuron can fire again. Places upper limit
on rate of neural firing. About 100 per second.
• Action Potential
o Stimulation causes sodium ions to enter axon (NA+).
o Stimulus has as to get above threshold (-55Mv).
o Once above threshold, the rest is automatic.
o Cell is repolarized by Potassium ions (K+) flowing out of the cell.
o Cell reestablishes resting state (-70Mv).
• The Synapse
o Terminals don’t touch
o “Synaptic gap”
o Chemical message
o Axon releases
o Dendrite picks up
• The visual input to our brains is the output of ganglion cells.
• Optic nerve is just a big bundle of the axons from all the ganglion cells in the retina.
• From this we construct our perception of everything in our vi