Last Class we ended with How to investigate Perception & Cognition • Ask your subjects (Introspectionism) • Look at S-R patterns (Behaviorism) • Infer mental processes (Cognitive Psychology) • from S-R patterns (Reaction Time, Accuracy) • from neural patterns (cognitive neuroscience)
Response Stimulus Information Processing Cognitive Psychology Representations Study stimulus-response relations to infer the underlying mental processes. The contents of the mind CAN be studied scientifically. How? Three models: The ‘black box’, the ‘jukebox’, the ‘mind box’
Response (output) Stimulus (input) The black box 1. Observe the Input/output relation 2 create a ‘model’ (abstract representation) to account for the I/O - requires a little bit of background knowledge (e.g., naïve physics, naïve biology), - It is a ‘functional’ model (how the box functions)
The black box: A ‘model’ Pull Force (push) Response (output) Stimulus (input) A • Is ‘A’ stick connected to the brown stick? • Can we run an experiment to find out? • vary input & measure output, from that I/O pattern make: • inferences about the internal constructs (i.e. create a functional model)
Input (selection) ABCDEFGHIJKLMN Output (a particular song) The jukebox As with the ‘black box’, we need to infer how it works (a functional model). We do this from the I/O pattern, and a little bit of background knowledge. ANY GUESSES?
Stack of disks selector A B . . . . . . Turntable How can we test this model? - Assume that selector always starts from top - Measure how long it takes to start playing
Move selector to next record Is record selected one? no yes Put record on turntable Functional Model of the ‘jukebox’ Move selector arm to top of stack Stack of disks selector A B . . . . . . • A hardware • A ‘functional’ architecture • (this is what Cog Psy studies)
The mind box • The same approach to study the functional architecture of the jukebox, can be applied to the study of the functional architecture of the mind. • Create an internal model by looking at the I/O pattern • Input (independent variable) • Output (dependent variable): usually Reaction Time (RT) • Example: Sternberg search (web). • A set of letters will appear briefly on the screen for you to study • The letters will disappear • 3 seconds later one probe item will appear. • Your task is to decide whether the probe item was in the initial list. Say ‘yes’ if the probe was in the list, ‘no’ if it wasn’t. READY?
delay P Z T A C H P Z T A C H Memory set (t1) - Set size can vary H • Probe (t2): • Present in set, or • Absent in set
Memory system X T N B D Create an input representation Compare the two representations Retrieve a representation from memory Y match Y X Y X respond “yes” no match last memory rep? yes respond “no” no • Sequential Model: Predictions • Larger memory set slower RT • ‘yes’ trials faster RT • ‘yes’ trials shallower slope
Memory system X T N B D Create an input representation Compare to all representations simultaneously match Y respond “yes” Y Y • Parallel Model: Predictions • Larger memory set same RT • ‘yes’ trials same RT • But caveats exist! respond “no” no match
Contrasting the two models • I.V.s (& levels): • ?? • ?? • D.V.:?