Dual Process Theories and the Fundamental Computational Bias

DUAL PROCESS THEORIES AND THE FUNDAMENTAL COMPUTATIONAL BIAS

Why do people with different levels of measured analytic ability sometimes favor different interpretations of reasoning tasks? One possible explanation comes from two-process theories of reasoning (Epstein, 1994; Evans, 1984, 1996; Evans & Over, 1996; Sloman, 1996). Although there are several two-process theories of reasoning that differ somewhat in their details, all agree on the general features of the two systems which, for simplicity, we label System 1 and System 2 (see Sloman, Chapter 22, this volume; Stanovich, 1999). System 1 is characterized as automatic, heuristic-based, and relatively undemanding of computational capacity. System 2 conjoins the various characteristics associated with controlled processing. System 2 encompasses the processes of analytic intelligence that have traditionally been studied by information processing theorists trying to uncover the computational components underlying intelligence.

For the purposes of the present discussion, the most important difference between the two systems is that they tend to lead to different types of task construals. Construals triggered by System 1 are highly contextualized, personalized, and socialized. They are driven by considerations of relevance and are aimed at inferring intentionality by the use of conversational implicature even in situations that are devoid of conversational features (see Margolis, 1987). The primacy of these mechanisms leads to what has been termed the fundamental computational bias in human cognition (Stanovich, 1999) – the tendency toward automatic contextualization of problems. In contrast, System 2’s more controlled processes serve to decontextualize and depersonalize problems. This system is more adept at representing in terms of rules and underlying principles. It can deal with problems without social content and is not dominated by the goal of attributing intentionality nor by the search for conversational relevance.

In summary, the biases introduced by System 1 heuristic processing may well be universal – because the computational biases inherent in this system are ubiquitous and shared by everyone. However, it does not necessarily follow that errors on tasks from the heuristics and biases literature will be universal (indeed, we have known for some time that they are not). This is because, for some individuals, System 2 processes operating in parallel will have the requisite computational power (or a low enough threshold) to override the response primed by System 1.

Using the distinction between System 1 and System 2 processing, we conjecture that in order to observe large cognitive ability differences in a problem situation, the two systems must lead to different responses. One reason for this prediction is that we assume that individual differences in System 1 processes (interactional intelligence) bear little relation to individual differences in System 2 processes (analytic intelligence). This is a conjecture for which there is a modest amount of evidence (see McGeorge, Crawford, & Kelly, 1997; Reber, 1993).

If the nature of the problem is such that the two systems generate opposite responses, rule-based System 2 – used disproportionally by those of high analytic intelligence – will not be diluted by System 1 nondifferentially drawing other subjects, lower in analytic intelligence, to the same response. Selection tasks can concern whether a factual rule is true (nondeontic tasks) or whether a rule about permission or obligation has been obeyed (deontic tasks). For example, in nondeontic selection tasks the two systems lead to different responses. A deductive interpretation conjoined with an exhaustive search for falsifying instances yields the response P & not Q. This interpretation and processing style is likely associated with the rule-based System 2 – individual differences in which underlie the psychometric concept of analytic intelligence. In contrast, within the heuristic – analytic framework of Evans (1984, 1989, 1996), the matching response of P&Q reflects the heuristic processing of System 1 (in Evans’ theory, a linguistically cued relevance response). In deontic tasks, both System 2 and System 1 processes (the latter in the form of preconscious relevance judgments, pragmatic schemas, or Darwinian algorithms; see Cheng & Holyoak, 1989; Cosmides, 1989; Cummins, 1996; Evans, 1996) operate to draw people to the correct response, thus diluting cognitive ability differences between correct and incorrect responders (see Stanovich & West, 1998a, for a data simulation).

The experimental results reviewed here (see Stanovich, 1999, for further examples) reveal that the response dictated by the construal of the inventors of the Linda Problem (Tversky & Kahneman, 1983), Disease Problem (Tversky & Kahneman, 1981), and selection task (Wason, 1966) is the response favored by subjects of high analytic intelligence. The alternative responses dictated by the construals favored by the critics of the heuristics and biases literature were the choices of the subjects of lower analytic intelligence. These latter alternative construals may have been triggered by heuristics that make evolutionary sense (Cosmides & Tooby, 1994, 1996), but individuals higher in a more flexible type of analytic intelligence (and those more cognitively engaged, see Smith & Levin, 1996) are more prone to follow normative rules that maximize personal utility for the so-called vehicle, which houses the genes. Cognitive mechanisms that were fitness enhancing might well thwart our goals as personal agents in an industrial society (see Baron, 1998) because the assumption that our cognitive mechanisms are adapted in the evolutionary sense (Pinker, 1997) does not entail normative rationality. Thus, situations where evolutionary and normative rationality dissociate might well put the two processing Systems in conflict. These conflicts may be rare, but the few occasions on which they occur might be important ones. This is because knowledge-based, technological societies often put a premium on abstraction and decontextualization, and they sometimes require that the fundamental computational bias of human cognition be overridden by System 2 processes.