Comparison Among Species

Transcription

1 Comparison Among Species Scientific Rationales for Comparison Theoretical: Provides insights into evolution and adaptive function of behavior (including our own) Insights into mechanism: discover deeper properties of processes shared by multiple species Practical: Using animals as models for investigating processes that can t be studied in humans (for ethical reasons) All of these rationales rely upon principle of evolutionary continuity 1/20/2005 ZOL 867 1

2 Primer on Evolution Natural patterns explained by evolutionary theory: Descent with modification (produces continuity of form and function among related species) Adaptive fit of organism to environment Darwin s Theory of Natural Selection: Variation (among members of an interbreeding population) Inheritance (like begets like) Struggle for existence, leading to differential survival and reproduction among different phenotypic variants Effects of natural selection (in stable environments over long time periods) Divergence among populations in different habitats (and ultimately the formation of new species) Adaptation: acquisition of traits that allow organism to meet challenges to survival and reproduction 1/20/2005 ZOL 867 2

3 Levels in Ethology Tinbergen s Four Questions: Alternative, complementary avenues of study prompted by the question Why does trait X have the properties that we observe? Physiology: sensory, neural, hormonal, integrative mechanisms Development: genetic and epigenetic causes of change over lifespan Phylogeny: origin and change in trait over evolutionary time Function: adaptive significance, or survival value 1/20/2005 ZOL 867 3

4 Another view of Levels Marr s Three Levels*: Distinct levels at which an information-processing device must be understood before one can be said to understand it completely. Computational Theory: goal of computation, and why it is appropriate Representation and Algorithm: How computational theory is implemented; especially how input and ouput are represented, and what is the algorithm for the transformation Hardware Implementation: Physical realization of algorithm *From Marr, D Chap 1 in Vision. Freeman 1/20/2005 ZOL 867 4

5 Animal Intelligence: Psychologists Radical behaviorism (Thorndike, Watson, Hull, Skinner): Goal was to search for general "laws of associative learning" Assumed it is futile to infer internal mechanisms from behavioral data Animals used as model for investigating general mechanisms Moderate behaviorism of E.C. Tolman Considered cognitive processes intervening between input and output Animals used as model ( I believe that everything important in psychology (except such matters... as involve society and words) can be investigated in essence through the continued experimental and theoretical analysis of the determiners of rat behavior at a choice point in a maze. ) Comparative Cognition (since early 1980s) Extension of "cognitive revolution" in psychology Continued psychological tradition of studying rats and pigeons in artificial environments, with anthropocentric bias (concepts defined in reference to human abilities)--this includes ape "language" literature 1/20/2005 ZOL 867 5

6 Animal Intelligence: Biologists Classical Ethology (Tinbergen, Lorenz, von Frisch etc.) Assumption: underlying processes CAN be inferred from behavior: "Physiology without breaking the skin" (Tinbergen) Mechanisms underlying behavior often found to be simpler than might appear at first glance, BUT much behavior implies complex informationprocessing abilities Behavioral Ecology (Oxford School) Focus on optimal decision-making (e.g., foraging, mate choice) Raised questions about underlying cognitive mechanisms "Cognitive Ethology" (D.R. Griffin-beginning in 1976) Examined whether animals have human-like mental states, including something like consciousness 1/20/2005 ZOL 867 6

7 Synthesis Bridging the gap Psychologists who have found ethology: Al Kamil, David Sherry, Sara Shettleworth, Randy Gallistel, Leda Cosmides, John Tooby Biologists who have found cognitive psychology: John Krebs, Alex Kacelnik, Robert Seyfarth, Dorothy Cheney An Ethological Approach (Kamil, Shettleworth) Careful study of clearly defined traits in ecological relevant situations Respect the distinctions of Tinbergen's Four Questions (Physiology, Ontogeny, Phylogeny, Function) 1/20/2005 ZOL 867 7

8 Adaptation as Design Who/what is the designer? Natural Selection What principles account for the selection of one design over others? Strategy for studying biological design Hypothesize specific function (or list set of hypotheses) Perhaps build model to capture quantitative details of functional hypotheses Test predictions of hypotheses Refine hypotheses Note: one assumes that there is a function, and one assumes optimal design Given description of the function of the system, how is the system implemented? For decision-making abilities of organisms, this strategy is consistent with Marr s approach in considering first the problem that the system seems to solve, then considering how it is solved? 1/20/2005 ZOL 867 8

9 An Example: Animal Foraging Animals that have to travel from home to a patch of food don t necessarily fill to capacity before traveling back home? Seems suboptimal. Is this a reflection of stupidness or cleverness of design? A model that investigates how such loading decisions may reflect optimal design Loading curve (constraint) Load gained Profit (Gain/time) may not be maximized by filling to capacity Time spent Optimal decision Patch time (decision) 1/20/2005 ZOL

10 Issues 1. Shettleworth s definitions of cognition and intelligence 2. The anthropocentric approach: using animals as models Is there an evolutionary continuum of cognitive mechanisms? The problem of convergent evolution 3. Function vs. mechanism Can insights into function provide insights into mechanism? Relate hypotheses about biological function to Marr s computational level Importance of presenting tasks in a manner that makes functional sense Adaptations vs. by-products vs. random noise 4. Tomasello vs. Cosmides/Tooby: where do they agree and disagree? 5. Social learning/cultural transmission/cultural evolution What is the critical difference between humans and other animals? Is it plausible that one key adaptation accounts for vast behavioral differences? 6. 1/20/2005 ZOL