In Two Minds surveys state of the art dual-process theories that have become enormously influential within modern psychology.

Dual-process theory holds that our mental lives are the result of activity of, and interactions between, two separate minds. The first mind – System 1 – is the mind that drives your car when you daydream. It is fast, implicit, subconscious, associative, and evolutionary ancient. System 2, in contrast, is the mind that generates directions. It is cognitively taxing, language-oriented, conscious, abstract, and a relative newcomer on the ecological scene.

Numerous flavors of dual-process theory have emerged over the years. The theory has emerged, relatively independently, from among the following traditions: social psychology, cultural psychology, psychometrics, developmental psychology, behavioral economics, and artificial intelligence. While such creative independence suggests a common biological substrate, little effort had been made to synthesize these different perspectives until now. This anthology, itself written to complement an interdisciplinary academic conference, represents a significant step towards such a harmonization.

One of my few complaints is that the lack of a canonical vocabulary made comparative analysis between chapters difficult. That said, the breadth of subjects treated was astonishing, and the writing quality was generally excellent. I should mention that most chapters have been made publicly available via their originating universities. The following chapters struck me as especially significant:

Ch 2: Evans: How many dual process theories do we need?
Book editor, and leader of the dual-process synthesis movement, Jonathan Evans presents his vision for dual-process theory development. He begins by presenting the clusters of properties associated with either mind. Insights from a diverse set of traditions are collected, with a particular interest taken in mediating inter-system communications. The chapter closes with a hybrid model of mental architectures. An ideal one-shot introduction to the field.

Ch 3: Stanovich: Distinguishing the reflective, algorithmic, and autonomous minds: Is it time for a tri-process theory?
Psychometric legend Keith Stanovich rocks the boat by his proposal to bifurcate System 2 into reflective and algorithmic types. The algorithmic mind is what IQ tests measure, and is correlated with working memory. It is also thought to be a measure of cognitive decoupling, echoing Aristotle’s famous dictum: “It is the mark of an educated mind to be able to entertain a thought without accepting it.” The reflective mind is, in contrast, driven by thinking dispositions. It is an explanation for how otherwise extremely intelligent people flounder – smarts need to be complemented by work ethic, mental resource-management, innovation, and other properties. The chapter closes with a stunning taxonomy of thinking errors, which explores in great detail how the heuristics and bias literature motivate the movement.

Ch 5: Carruthers: An architecture for dual reasoning
Philosopher of mind Peter Carruthers explores concepts developed in his acclaimed work, Architecture Of Mind. His argument, inspired by the massive modularity thesis of evolutionary psychology, moves at a brisk pace. Breathtaking structural diagrams are presented, and grounded in wide swathes of empirical data. Carruthers’ main thesis is that this architecture is shared between System 1 and System 2: when consciousness takes over, it disconnects the modules from the action production systems to simulate various outcomes.

Ch 8: Thompson: Dual-process theories: a metacognitive perspective
While theorists have much to say about the different roles of either system, little is known about how they interact. Thompson seeks to fill this gap with an account of the emotional payload people experience when, say, they solve a riddle. Such Feelings Of Rightness (FORs, also known as yedasentience) are transmitted from System 1 to System 2, which only decides whether to intervene when the FOR is insufficiently strong.

Ch 10: Buchtel, Norenzayan: Thinking across cultures: implications for dual processes
It is an unfortunate truth that many psychological studies generalize their conclusions even though their polled subjects consist entirely of American psychology undergraduates. In this important chapter, Buchtel and Norenzayan explain why such a scope conceals the true breadth of human cognitive diversity. Cross-cultural studies are analyzed, with the conclusion that the System 2 characteristics of East Asian peoples consistently diverge from Occidental students. Subjects immersed in East Asian culture tend to focus more attention at contextual features of problems. The implications of this difference – for theory modification, and an account of how culture shapes ontogeny of cognition – are explored.

Ch 11: Sun, Lane, Matthews: The two systems of learning: architectural perspective
Artificial intelligence research Ron Sun reviews his architectural innovation CLARION. Since this computational innovation is well-documented at length elsewhere (including Wikipedia), Sun zeroes in on its relationship with dual-process theorizing. Specifically, and in contrast with Carruthers above, his software posits two distinct computational entities, and is able to recreate human idiosyncrasies via an exploration of the systems’ interactions.

Ch 13: Lieberman: What zombies can’t do: a social cognitive neuroscience approach to the irreducibility of reflective consciousness
For centuries, academics have countenanced philosophical zombies: what would it mean if a human being could behave normally but lack conscious experience? Lieberman here harnesses dual-process theories and neuroimaging data to explore the more focused question on whether such a phenomenon is nomologically possible.

Ch 15: Saunders: Reason and intuition in the moral life: a dual-process account of moral justification
Saunders examines the phenomenon of moral dumbfounding, via one of its manifestations regarding incest. Most people, when asked whether a short story about incest represents something morally wrong, will answer affirmatively and provide their reasons. However, when the storyteller removes the offending reasons (both parties are psychologically unharmed, there is no risk of pregnancy, etc), subjects generally maintain that the behavior is wrong, yet they cannot explain why they think so. The author goes on to explain how such moral dumbfounding is the result of clashing moral conclusions between the still-outraged System 1 and the deprived-of-reasons System 2.

This is my favorite cognitive science text to date.