Part of the sequence: Rationality and Philosophy

Whether you're doing science or philosophy, flirting or playing music, the first and most important tool you are using is your mind. To use your tool well, it will help to know how it works. Today we explore how your mind makes judgments.

From Plato to Freud, many have remarked that humans seem to have more than one mind.¹ Today, detailed 'dual-process' models are being tested by psychologists and neuroscientists:

Since the 1970s dual-process theories have been developed [to explain] various aspects of human psychology... Typically, one of the processes is characterized as fast, effortless, automatic, nonconscious, inflexible, heavily contextualized, and undemanding of working memory, and the other as slow, effortful, controlled, conscious, flexible, decontextualized, and demanding of working memory.²

Dual-process theories for reasoning,³ learning and memory,⁴ decision-making,⁵ belief,⁶ and social cognition⁷ are now widely accepted to be correct to some degree,⁸ with researchers currently working out the details.⁹ Dual-process theories even seem to be appropriate for some nonhuman primates.¹⁰

Naturally, some have wondered if there might be a "grand unifying dual-process theory that can incorporate them all."¹¹ We might call such theories dual-system theories of mind,¹² and several have been proposed.¹³ Such unified theories face problems, though. 'Type 1' (fast, nonconscious) processes probably involve many nonconscious architectures,¹⁴ and brain imaging studies show a wide variety of brain systems at work at different times when subjects engage in 'type 2' (slow, conscious) processes.¹⁵

Still, perhaps there is a sense in which one 'mind' relies mostly on type 1 processes, and a second 'mind' relies mostly on type 2 processes. One suggestion is that Mind 1 is evolutionarily old and thus shared with other animals, while Mind 2 is recently evolved and particularly developed in humans. (But not fully unique to humans, because some animals do seem to exhibit a distinction between stimulus-controlled and higher-order controlled behavior.¹⁶) But this theory faces problems. A standard motivation for dual-process theories of reasoning is the conflict between cognitive biases (from type 1 processes) and logical reasoning (type 2 processes).¹⁷ For example, logic and belief bias often conflict.¹⁸ But both logic and belief bias can be located in the pre-frontal cortex, an evolutionarily new system.¹⁹ So either Mind 1 is not entirely old, or Mind 2 is not entirely composed of type 2 processes.

We won't try to untangle these mysteries here. Instead, we'll focus on one of the most successful dual-process theories: Kahneman and Frederick's dual-process theory of judgment.²⁰