As a psychologist who studies sentence comprehension and holds a joint appointment in the departments of psychology and linguistics, I have frequent opportunities to observe the interaction, or lack thereof, between the two disciplines. Although cognitive psychology and formal linguistic theory share some common history in Chomsky’s (1959) pivotal review of Skinner’s (1957) book on language behavior, these two disciplines have not continued to influence one another to the degree one might expect. For example, theoretical developments in syntax have rarely if ever been motivated by an experimental finding about sentence comprehension. In fact, there is good reason for this. I argue that most psycholinguistic data is irrelevant to formal linguistic theory. Nonetheless, there may be a subset of psycholinguistic data that formal linguists ought to consider. I attempt to delineate this hypothetical subset, using the argument/ adjunct distinction as an example.