Primer Decision makingJeffrey D. SchallDaily we encounter numerousalternative courses of actionamong which we must choose.These alternatives vary incomplexity and consequence.Some alternatives are consideredlightly, such as the way to turn onthe journey home. Others requirefervent deliberation, such asHamlet’s agonizing decisionwhether to end his life. The neuralbasis of decision making has beenreviewed extensively [1–4], so thegoal of this primer is to orient theinterested reader to this growingliterature with emphasis onneurophysiological work, ratherthan the expansive literature onfunctional brain imaging andneuropsychology. Another goal isto articulate the key concepts ofchoosing, deciding, intending andacting [5,6]. Dwelling onterminology may seem anunnecessary tangent, but sciencetravels on its vocabulary —inconsistent and vague terms canonly yield confusion. This is all themore important when the object ofthis scientific investigationultimately is nothing less thanhuman agency.ChoiceA choice is required when anorganism is confronted withalternatives for which an action isrequired to acquire or avoid one ofthe alternatives because of a desire,goal or preference. In its mostfundamental sense, a choice is anovert action performed in thecontext of alternatives for whichexplanations in terms of purposescan be given. Consider the optionsof selecting between twoenvelopes, A and B, containingdifferent amounts of money(Table 1). Choice #1 is easy becauseit offers the guarantee of obtaining$1,000 by selecting envelope A,instead of $1 by selecting envelopeB. Choice #2 requires more thoughtbecause the amount of money isunpredictable, but a suitableanalysis leads to a wise choice.Choice #3 requires deliberation tocontend with a paradox of choiceprediction [7]. Regardless of thecomplexity of the alternatives,though, you must execute yourchoice through some action, suchas grasping one of the envelopes.Choices have particularcharacteristics. First, choices areevaluated as good or badaccording to whether goals areachieved and consequences are asexpected. Second, choices taketime; a choice process evolvesfrom a state of more or lessequipotentiality immediately afterthe alternatives are presented to astate of commitment before theovert action is performed. Third,with prior knowledge of thealternatives and preferences, somechoices can be predicted.According to this definition,neurophysiological correlates ofchoice behavior are studiedwhenever an experimental subjecthas alternative responses. This hasbeen studied, for example, withpsychophysical discrimination [8]and visual search [9]. With easilydistinguished alternatives andpredictable reinforcements, likechoice #1, the neuralrepresentation of the stimuli isresolved unambiguously, leading toan earlier and more accurate motorresponse. When the stimuli aremore difficult to distinguish [10,11]or the reinforcement becomes lesspredictable [12,13], like choice #2,the neural representation of thealternative choices takes more timeto resolve, and that representationcan be modulated by the expectedvalue of the choice.Finally, although noneurophysiological studies havebeen conducted in the context ofNewcomb’s paradox, new studiesare exploring situations in whichthe experimental subject choosesalternatives supposedly based onthe actions of another agent [14].Choices made in the context of thechoices of another agent are alsoguided by reinforcement history,but also with some sensitivity to thestrategies employed by the otheragent. This progression ofexperimental conditions shouldmake clear that some choices areeasy and others are hard. Whenalternatives are vague, payoffs areunclear and stakes are high, then itseems natural to regard thesubjects as making a decisionbefore they act.DecisionThe term decision is used casuallyand technically in several, notentirely consistent senses. On theone hand, decision theorydescribes the characteristics ofeffective behavior in relation toexpected consequences [15]. Forexample, the best solution to thesecond choice in Table 1 is toselect the envelope for which theproduct of the probability and themonetary amount is greatest. Thisis the domain of decision theoryand related frameworks, such aseconomics and game theory. Avery active area of inquiry of latehas employed concepts ofdecision theory and relateddisciplines in the investigation ofthe neural preliminaries of choicebehavior [16].Table 1. Choices based on predicted monetary reward.Envelope A Envelope BCondition Payoff Condition Payoff#1 100% $1,000 100% $1#2 9% $10,000 90% $1,000#3 100% $1,000 If only B $1,000,000If A and B $0Two envelopes labeled A and B are offered for you to obtain. Choice #1 is between twotransparent envelopes; envelope A contains $1,000 and envelope B, $1. Choice #2 isbetween two opaque envelopes. Envelope A has a 9% chance of containing $10,000 andenvelope B has a 90% chance of containing $1,000. Choice #3 is Newcomb’s paradox.Envelope A is transparent and contains $1,000. Envelope B is opaque and will contain either$1 million or nothing. You will be given the choice of taking either B alone or A with B.Before you are presented with the envelopes, an infallible brain scan is done to predict yourchoice. If the prediction is that you will choose only envelope B, then $1 million is placed init. If it is predicted that you will choose both envelope A and B, then nothing is put inenvelope B.MagazineR9On the other hand, we can referto a decision as a process thatresults in the overt act of choosing.Such a process must have aparticular architecture, butmeasures of outcome derived fromdecision theory do not uniquelyspecify mechanism. Decision as aprocess has two logically andpractically distinct meanings. Wemust distinguish between decideto, which is a selection betweenalternative actions, and decidethat, which is a selection betweenalternative categories of an imageor concept. The logical distinctionis easy to see. You can decide thatfalsely, but you cannot decide tofalsely — it is not intelligible. Thedecision that envelope B alwayscontained $1 million is false, but inwhat sense can you decide falselyto take envelope B? You just take itor you do not. Decide to, likechoosing, is judged as good orbad, but not as true or false.The fact that choices can bepredicted makes it possible tochoose in advance: it is intelligibleto say, “I will choose envelope Bwhen given the opportunity.” Thissense of choice is more related todecision. But