You study a restaurant menu and decide to order steak rather than salmon. But when the waiter describes the lobster special—which, after all, is seafood, too—suddenly lobster trumps steak. Without reconsidering the salmon, you order lobster, all because of a process called transitivity.
Transitivity underlies rational economic choice. If you prefer lobster to steak and steak to salmon, then you will prefer lobster to salmon.
Work completed in the laboratory of HMS Professor of Neurobiology John Assad suggests that transitivity is encoded at the level of individual neurons in the orbitofrontal cortex. These neurons behave in a menuinvariant way. That is, the neurons respond the same to steak regardless of whether it’s offered against salmon or lobster.
“This study provides a key insight into the biology of our frontal lobes and the neural circuits that underlie decision making,” Assad says. “We can, in fact, compare apples to oranges, and we do it all the time. This research sheds light on how we make these types of choices.”
Scientists have linked faulty decision making evinced by such behaviors as eating disorders and compulsive gambling to frontal lobe damage. And researchers are just beginning to probe normal decision making at the level of individual neurons, venturing into the neuroeconomics field.