Modern Cognitive Psychology
Many psychologists became dissatisfied with the limitations of Behaviorism.
This led to the “Cognitive Revolution” of the early 1960’s. It wasn’t as sudden as the name implies. It was a more gradual process than the name implies. Study of internal states and processes became a focus of experimental psychology once again. It was a reappreciation of the roots of psychology with Wundt.
Two Key Players
George A Miller(b. 1920)
An early supporter of Chomsky’s theory about language.
Ulric Neisser (b. 1928)
He was a student of Miller. He wrote the first systematic account of the new field (“Cognitive Psychology,” 1967).
Developments in the 1970’s
The rise of cognitive science in the mid-70’s. There are important differences between it and cog psych. Cognitive science is interdisciplinary and its approach seeks to explain how the mind works. It is an attempt to bridge the gaps that separate academic disciplines.
Cognitive psychology is part of a larger whole. It is a subfield of psychology and a subfield of cognitive science.
Methods and Tactics
Cognitive processes possess three atributes which make them hard to study:
(1) Many (most?) are not available to conscious introspection.
(2) They are covert (not directly revealed by behavior).
(3) They occur very quickly (tenths of a second)
How to measure?
Most cognitive measures are indirect. Indirect methods are used in science quite a bit.
Inferences are made based on behavior. (People come to lab and do certian things then we observe how they respond based on these contexts.)
A properly designed study will allow us to infer underlying cognitive processes.
What we measure during the course of an experiment.
(1) reaction time
how long it takes to react to a stimulus. (assumptions: cognitive operations are carried out over time. Increases in cognitive processing should be revealed by increases in reaction time.) Time itself isn’t cognition but the two are intimately linked. Reaction time units: milliseconds. 1/1000th of a second long.
How do you measure periods of time that small. Today it’s a trivial problem. Computers operate on the order of nanoseconds.
A century ago it was a difficult problem. To get this accuracy, researchers used complex and expensive clocks.
Another approach: Instead of trying ot measure the subjects’ responses precisely, one could control the display of a stimulus precisely. This lead to the development of tachistoscopes (T-scopes)(used until 1970’s). These were machines that controlled the to of stimuli down to millisecond accuracy. Using a Tscope: Experimenter could show a subject a stimulus for a very brief, fixed period of time (an exposure duration). You could start with very brief exposure (too short to identify the stimulus) and gradually increase their length until the subject can identify the stimulus.
What happens if subject gets the stimulus wrong? Mistakes cab for cat. This is due to us reading left ot right. It can be useful to look for patterns of mistakes people make.
(2) Error rate
what happens when system breaks down and does something that’s incorrect. This is accomplished by keeping track of errors made by subjects. If errors show a pattern (they aren’t random) it’s possible to make inferences about underlying cognitive processes. High reaction time usually have high error rate.
(3) Percent correct
a measure of subject’s ability (accuracy, comprehension, etc.). Used in memory research to study forgetting.
Although flawed, it can still be useful. A variant of introspection is called the think-aloud protocol. This is very common in problem solving research.
(5) Scaled Ratings
Is a collie a typical member of the category dog? Then you rate on a scale.
(6) Eye movements
A computer, using a laser can track eye movements. Can be used to determine where a subject is looking and for how long. Used to study reading or Web-page design.
(7) Cerebral blood flow (CBF)
subject drinks glucose with a radioactive marker. Glucose is an energy source and is taken up by more active parts of the brain. More active areas will receive more radioactive tag. As the isotope decays, radiation is emitted. Particles will shoot out of subjects head. Emission detectors create a map of active brain regions. Metabolic uptake of glucose.
(8) Event-related potentials (ERP’s) or Evoked Potentials
used to measure electrical activity in various parts of the brain. Electrodes placed on subjects scalp. Subjects asked to process stimuli. Subject is asked to do a task over and over and over again. they need a lot of trials to separate signal from extra noise in brain. Average all the waves together to get the signal. Pizzas can’t cry. A sentence such as, the pizza was too hot to cry is called a semantic anomaly. This huh? response can be detected by averaging together many trials in which subjects see anomalous sentences. When subjects read this sentence, there was a negative spike about 400ms after the word cry was read. This is called the N400 component.