Green’s Tri-Level Hypothesis

1. Green’s Tri-Level Hypothesis • Behavioral: a person’s performance on specific experimental tasks • Cognitive: the postulated cognitive or affective systems underlying the behavior • Biological: the nature of the brain systems as affected by genetic, environmental, and social factors that mediate the cognitive systems

2. The Basic Questions • For the normal, typical adult, what is the human capacity to X? • How does a normal, typical adult (exercise his or her capacity to) X? • How does the capacity to X of the normal, typical adult interact with the rest of his or her cognitive capacities?

3. Computational Assumption(mechanistic, but not reductive) • Linking Assumption: The human mind or brain is a computational device (computer); hence, human cognitive capacities consist, to a large extent, of a system of computational capacities • System Assumption: A computer is a device capable of automatically inputting, storing, manipulating, and outputting information in virtue of inputting, storing manipulating, and outputting representations of that information. • These information processes occur in accordance with a finite set of rules that are effective and that are, in some sense, in the machine itself

4. Representational Assumption • Linking Assumption: The human mind or brain is a representational device; hence, human cognitive capacities consist of a system of representational capacities. • System Assumption: A representational device is a device that has states or that contains within it entities that are representations. Any representation will have four essential aspects to its being a representation.

5. 4 essential aspects essential for a representation • will be realized by a representation bearer • will represent one or more representational objects • representation relations will be grounded somehow • will be interpretable by (that is, will function as a representation for) some currently existing interpreter

6. Methodological Assumptions • Basic questions can be presented in narrow information processing terms • Study of human cognition can focus on the individual in the natural environment; culture and society gain their effects through mental representation • Cognition can be studied independently from affect and personality • Each cognitive capacity can be studied independently • We can distinguish ‘normal’ from ‘abnormal’ cognition • Adults are alike enough to allow for talk of ‘typical’ cognition

7. More Assumptions • Explanatory strategy of cognitive science is sound • Scientific methods rule (empirical data!) • Complete theory of cognition requires contributions from all cognitive science’s subdisciplines • Information processing answers to basic questions are constrained by neuroscience

8. Marr’s Levels of Explanation (equal to Green’s levels) • Computational • Task, behavior: What do people do, given specific tasks • Algorithmic • Cognitive: What cognitive of affective systems underlie the behavior • Implementational • Biological, brain: The basic systems, as affected by genetic, environmental, and developmental factors

9. Summary • Cognitive science aims to understand: • The processes and representations underlying intelligent action in the world • It does so by building and testing: • Explicit models of these processes • Complete models have at least 3 levels: • Computational (behavioral) • Algorithmic (cognitive) • Implementational (biological)