Control of Cognitive Processes

We define the problem addressed at the eighteenth Attention and Performancesymposium as that of explaining how voluntary control is exerted over the organizationand activation of cognitive processes in accordance with current goals, without appealingto an all-powerful but ill-defined “executive” or controlling “homunculus.” We providebackground to the issues and approaches represented in the seven parts of the volume andreview each chapter, mentioning also some other contributions made at the symposium. Weidentify themes and controversies that recur through the volume: the multiplicity of controlfunctions that must be invoked to explain performance even of simple tasks, the limits ofendogenous control in interaction with exogenous influences and habits, the emergence ofcontrol through top-down “sculpting” of reflexive procedures, the debate between struc-tural and strategic accounts of capacity limits, the roles of inhibition and working memory,the fertile interactions between functional and neural levels of analysis. We identify impor-tant control issues omitted from the symposium. We argue that progress is at last beingmade in banishing—or fractionating—the control homunculus. When we invited the psychologists and neuroscientists whose contribu-tions constitute this volume to speak at the Eighteenth InternationalSymposium on Attention and Performance, we declared the theme of themeeting to be “Control of Cognitive Processes: Banishing the Homun-culus.” We took the provocative subtitle from a contribution by the lateAlan Newell to the eighth symposium: A major item on the agenda of cognitive psychology is to banish thehomunculus (i.e., the assumption of an intelligent agent (little man) resid-ing elsewhere in the system, usually off stage, who does all the marvelousthings that need to be done actually to generate the total behavior ofthe subject). It is the homunculus that actually performs the control pro-cesses in Atkinson and Shiffrin’s (1968) famous memory model, who stilldoes all the controlled processing (including determining the strategies)in the more recent proposal of Shiffrin and Schneider (1977), who makesall the confidence judgments, who analyses all the payoff matrices andadjusts the behavior appropriately, who is renamed the “executive” inmany models (clearly a promotion).... (Newell 1980, 715) The eighteenth symposium, twenty years later, seemed a suitable occa-sion to take stock of progress on this agenda item. On the one hand, it isour impression that, far from leading the furtive life of a fugitive, thehomunculus has continued to parade about in broad daylight, its powers largely intact and indeed dignified by even grander titles—not merelythe “executive” but the “central executive,” or the “supervisory attentionsystem,” or the “anterior attention system”—and flagrantly laying claimto prime real estate in the frontal lobes. On the other hand, there has beena substantial increase in research by neuroscientists, neuropsychologists,and experimental psychologists on “executive” functions, and on inter-actions between endogenous (voluntary) and exogenous (stimulus-driven) control of cognitive processes. We may now have a sufficientdatabase for a serious attack on the problem to which the control homun-culus has been the default solution. 1.1 THE PROBLEM OF VOLUNTARY CONTROL Viewed from a subjective perspective, the problem of control is as old asphilosophical speculation about the nature of our mental faculties. Wefeel able to exercise voluntary control over our thoughts and behavior, yetwe also experience limitations to that control: we sometimes feel at themercy of habits, impulses, compulsions, obsessions, or reflexes; we dothings we apparently did not intend to do and leave undone things weintended to do. Can the seemingly voluntary aspects of our mental life begiven the same sort of mechanistic causal explanation that we happilyapply to the more reflexive aspects? If they can—if our exercise of vol-untary control is no less determined than our reflexes—then in whatsense do we have free will?Posed in these subjective terms, the problem of control carries with itconsiderable philosophical, theological, and moral baggage. The compu-tational theory of mind that now underlies cognitive psychology andneuroscience provides us with a more objective perspective from whichto pose the problem. The mind/brain evidently contains many represen-tations of information (perceptual, semantic, motoric, etc.), and proce-dures for translating between and transforming those representations.The performance of any one cognitive skill involves only a subset of theseresources, which must be organized in a particular fashion for the task athand, and defended against disruption by other influences. Althoughsome processes (such as the earliest stages of sensory processing) may betriggered by appropriate input in an inflexible manner regardless of cur-rent goals, others may not. These other processes may have to be flex-ibly enabled or disabled, connected or disconnected, tuned, organized,directed, scheduled, and monitored (or some subset of these) to accom-plish particular goals. The goals often change from moment to moment.The problem of voluntary control is thus: How are goal-relevant orga-nizations of particular mental resources created or activated, and howare goal-appropriate processes triggered, when they are appropriate, andsuppressed when they are inappropriate? And what constrains the flexi-bility of this deployment?