April 23, 2008
Presenter: Robb Rutledge
Respondent: Ryan Booth
On Scientific Method
Robb’s presentation was an enlightening talk that began from a bird’s eye view with a discussion of the scientific method and then converged to a discussion of his specific neuroeconomic research. Several challenging questions were raised throughout the dinner, from Robb’s initial query – “What is science?” – to the final question posed by Kate – “How do we interpret the notion of ‘reason,’ given the newfound knowledge gleaned from neuroscience?” While reflecting upon Robb’s presentation, one recurring theme jumped out at me – the notion of identity. Namely, how does a discipline define itself and its research agenda, especially once members of its community begin engaging in interdisciplinary collaboration? My response will first comment on Robb’s talk and then conclude with some thoughts related to this notion of identity.
Segueing from Kurt’s previous presentation, Robb began with a brief discussion of the scientific method. Referencing his own research conducted in New Caledonia, Robb described the process of finding an interesting question, postulating a theory and then testing the theory via observation and data. The New Caledonian Crow is the only non-primate animal that uses tools, and Robb explained how he spent two months studying this unique bird. Much like how humans favor a dominant hand, these crows exhibit a dominant side of their body when using sticks and leaves to “fish” larvae out of small holes in rotting wood. To systematically verify this conjecture, for several weeks Robb repeatedly observed a small set of crows while they “fished” larvae out of a rotting stump.
After recounting his experience, Robb reflected that, while his research yielded an interesting discovery and increased the body of human knowledge, the project has nevertheless had a negligible impact on society. As many scientific endeavors are not directly “relevant” to society, Robb thus offered the following definition of science: A discipline in which individuals investigate fascinating phenomena for curiosity’s sake. Interestingly enough, most, if not all, academic disciplines satisfy this criterion – scholars of linguistics, philosophy and history all study interesting phenomena that are often unrelated to the pressing societal matters of the day. The next logical question is thus, what distinguishes the natural sciences from other disciplines?
The presentation then transitioned into an overview of the foundational neuroscience research that underlies Robb’s current project. The discussion began with a physiological description of the brain and progressed to an explanation of the connection between dopamine and habit formation. Robb and Jennifer described how some addictive drugs, such as cocaine, prohibit the reuptake of dopamine and thus generate increasingly pleasurable highs for users, suggesting there exists a relationship between dopamine firing and individual choice.
Based on this relationship and experimental evidence, neuroscientists formulated the dopaminergic reward prediction error (DRPE) hypothesis, a theory suggesting that dopamine level is related to the difference between an individual’s expected and actual reward. To illustrate this conjecture, consider the following example: Joe enters a lottery where he will win an amount of money between $0 to $20. If Joe expects to win $10 and actually wins $10, then his dopamine level would remain constant. If, on the other hand, Joe expects to win $10 and actually wins $15, then his dopamine level would increase, whereas if Joe expected to win $10 and actually won $5, then his dopamine level would decrease.
In past studies, neuroscientists have tested the DRPE hypothesis almost exclusively using a learning model in which individuals update their expectation of the magnitude of a reward through time. Robb discussed, however, that this standard model is overly restrictive by assuming considerable structure about the specific learning process. The model, for example, implicitly supposes that the learning process is a linear function of past rewards, a completely arbitrary assumption. Consequently, while the standard DRPE model fits the data well, it nevertheless may be misspecified because of these onerous restrictions.
To attempt to verify the DRPE hypothesis with a more robust model, Robb explained how he and his coauthor teamed with two economists. Their coauthors devised three relatively simple axioms that are necessary conditions for the DRPE hypothesis to be correct. In other words, experimental data violating any of these axioms would refute the DRPE hypothesis. To test these axioms, Robb designed and conducted an experiment in which subjects were placed in an fMRI machine and were repeatedly asked to choose which of two lotteries they wanted to play. For instance, subjects were asked whether they wanted to play lottery 1, yielding $0 for sure, or lottery 2, yielding a $5 gain with 75% probability and a $5 loss with 25% probability. After the choice was made, the patients were told the outcome of their chosen lottery and then were presented with another choices problem. In the end, Robb’s experimental results satisfied the axioms, thus providing additional support for the DRPE hypothesis.
Interestingly, at the conclusion of his presentation, Robb mentioned that, in his opinion, neuroeconomics is far from symbiotic relationship. While neuroscientists benefit by working with economists who specialize in game theory and axiomatic modeling techniques, it isn’t readily apparent what economists gain from working with neuroscientists. As our discussions indicated, many economists are skeptical of neuroeconomics – while neuroscience is fascinating, the critics claim, economists shouldn’t be concerned with an individual’s internal decision-making processes per se. Economics is about choice, they maintain, and additional information about the specific mechanics leading to those choices are of little interest. Nevertheless, a small group of economists are actively pursuing interdisciplinary work with neuroscientists, and such work is becoming increasingly prevalent.
Reflecting upon this schism and the other presentations we’ve seen this semester, I noticed that one theme we’ve repeatedly revisited throughout the semester is the struggle that scholars face in defining their field of specialty. Robb and Kurt, for instance, both went right to the heart of the matter by attempting to define science, a task that is far from straightforward. Likewise, Abby confronted a similar issue when discussing her own discipline’s recurring struggle to establish a definition of art and determine art’s “place” in the modern world. Tafadzwa also touched on identity, as some legal scholars debate the appropriateness of the notion of “universal human rights.” Moreover, identity becomes even harder to define once the line between previously disjoint entities begins to blur, as is the case with the recent collaboration between neuroscience and economics. The recent emergence of this interdisciplinary collaboration has forced economists, for instance, to confront controversial, difficult questions and spurred impassioned debate about the discipline’s identity. Should economists search for alternatives to the “rational agent” approach to modeling? If so, will neuroscience contribute in finding this new approach? And, most elementary, what constitutes economics research? As Abby alluded in January, a discipline’s identity is constantly evolving as new discoveries, techniques and examples are incorporated into a field’s canon. Perhaps, then, we as researchers spend more time redefining our disciplines’ identities than we realize, and new sea changes in thought, such as the emergence of abstract art or interdisciplinary collaboration, simply accentuate this constant evolution.