How is Two Minds Theory Different?

TMT is strongly based on the work of behavioral economists like Daniel Kahneman, Amos Tversky, and Richard Thaler. Kahneman's 2011 book Thinking, Fast and Slow popularized the idea that people have two distinct mental systems. Two Minds Theory also draws heavily on the work of cognitive neuroscientists like Jonathan Evans and Keith Stanovich. Our version of Two Minds Theory differs from its predecessors in two key ways:

1. We propose that only the intuitive system operates fast enough to generate behavior. This differs in particular from Kahneman, who argues that the narrative system is "lazy" and usually inactive, but can become activated and take control of behavior away from the intuitive system. We instead suggest that the intuitive system is identical to Kahneman's "experiencing self" which functions in the moment, and that the narrative system is identical to Kahneman's "remembering self" which can only comment on experiences after they occur.

2. We propose that temporal immediacy is the most important differentiator between the two systems, with the intuitive system being activated whenever questions or situations are concerned with present experiences. The narrative system is activated when questions are asked about the past or the future. We suggest that many empirical findings, such as the gap that often occurs between people's intentions and their behaviors, can be explained based on this methodological feature.

What is Two Minds Theory?

Two Minds Theory is an adaptation of previous work in cognitive neuroscience, behavioral economics, and health psychology. The diagram below shows what happens when someone encounters a new situation (stimulus). Version 1 of the model, below, shows that two separate mental systems are set off at the same time:

The intuitive system registers perceptions about the stimulus, which trigger automatic responses and habitual responses that were stored in procedural memory. At the same time, the narrative system allows the person to make conscious judgments about the stimulus, leading to a conscious experience and then to narratives that take the form of propositions, attitudes, or beliefs which can be expressed in language. The narrative system also controls attention, which can be used to generate awareness of intuitive-level processes that are usually outside of consciousness.

Crucially, behavior is the result of the intuitive system's work only. This happens because the narrative system is simply too slow to generate behavior in the moment. But existing narratives (created and stored based on prior experiences with similar stimuli) do become part of the intuitive system's selection of behavior, in addition to immediate physiological reactions and previously learned responses. The exact mechanism by which the intuitive system selects behavior is still unknown, but it is tied to the real or imagined consequences that the behavior is projected to have. TMT proposes that selection of behavior happens outside of language and consciousness. In our view, the fact that behavior happens outside consciousness doesn't necessarily imply a philosophy of determinism.

The idea of "temporal immediacy," shown as a horizontal line between the Narrative and Intuitive systems in our original diagram, was intended to show the separation between narratives and intuitively-generated behaviors. The line isn't a barrier that can be crossed, simply because the Narrative system doesn't get involved until after the behavior occurs. Our original diagram is good for illustrating the operation of two independent systems, but the time element is hard to see -- really, the upper part of the diagram should be shifted about half a page to the right!

To address this point of confusion, CU Nursing PhD student Laurel Messer proposed the following alternative representation, which more clearly shows the time-delay inherent in the Narrative system:

In this second representation, the stimulus initially triggers an Intuitive system response, which includes both a reaction (perceptions, emotions, interpretations) and then a behavior. The intuitive response still occurs outside the level of consciousness, and the first two circles in this cycle (reading from the point where the stimulus comes in) correspond to the part below the line in version #1 of the theory. The behavior then leads to some immediate consequence (something not represented in version #1), which both teaches the Intuitive system what to do or avoid the next time around, and also becomes part of the resulting Narrative about the event.

Only after these things have all taken place does the Narrative system get to have its say. The Narrative response is something that the Intuitive system takes into account the next time it encounters a similar stimulus. This version of the diagram more clearly shows the "temporal immediacy" difference between the two systems -- the Intuitive System is fast and the Narrative System is slow. It also illustrates the futility of trying to talk oneself into a different behavior pattern, because conscious thought takes place after the behavior occurs. That's not to say a different way of thinking can't help, but it will help later, in future iterations of the cycle, and it will help only if it informs an Intuitive response that's below the level of consciousness. In other words, a new Narrative doesn't help unless you truly believe it "in your heart, in your gut, in your bones," as people say, and not just intellectually.

What is the Biological Basis for this Theory?

The intuitive system is based in subcortical areas of the brain:

  • the nucleus accumbens is the brain's reward center and helps to select actions based on their expected consequences.
  • the amygdala, hypothalamus, and other parts of the limbic system are involved in emotional activation, including the "fight or flight" response.
  • the striatum initiates actions and is involved in procedural memories.
  • the insular cortex makes snap decisions, such as the heuristic responses and behavioral biases identified by behavioral economists.

The narrative system links to many brain areas, but is strongly dependent on activity in the prefrontal cortex. Our version of TMT suggests that the prefrontal cortex is not an "executive" in the sense of choosing or directing behaviors. Instead, it is more like a commentator that develops narratives based on behaviors as they occur. The prefrontal cortex connects to other brain areas that also support narrative thought:

  • the hippocampus helps to form and access declarative memories.
  • the thalamus is activated when deliberately paying attention to something, and helps to interpret perceptual input.
  • the motor cortex initiates actions, or perhaps more importantly inhibits actions that have been already initiated by an intuitive process.
  • the amygdala is also connected to the prefrontal cortex, a pathway that may be involved in inhibiting emotional reactions.
  • the cingulate cortex lies in between the prefrontal cortex and the subcortical areas, and may be involved in conscious experience.

How does TMT Relate to Other Theories of Human Behavior?

Classical and medieval theories of mind posited a human soul with multiple parts:

  • Plato proposed a metaphor of "two horses," with a noble horse (reason) directing behavior in good directions, an evil and willful horse (human nature) pulling toward selfish and short-sighted actions, and a "charioteer" (the soul) choosing between these alternatives. See our related blog post, "Isn't Plato an Out-of-Date Reference?"
  • Aristotle suggested a four-part soul, and said that the person who actually wants to do good (and does it automatically, i.e. via the intuitive system) is better than the person who does good only by force of will (i.e., through conscious effort). In Aristotle's view the habit of good actions (called virtue) can be developed through practice, similar to our principle of training the intuitive system.
  • St. Paul wrote that people often do things that they wish they would not, and fail to do things that they wish they would. This is a classic formulation of the intention-behavior gap. Great thinkers in other traditions, such as Mahatma Gandhi, have noted this gap as well.
  • Medieval theologians and philosophers built on these frameworks. In the Catholic tradition, St. Augustine proposed a distinction between earthly and heavenly things that closely corresponds to Plato's two horses, with reason or the good horse now also identified with holiness. In the Protestant tradition, Martin Luther wrote that people's behavior is determined by a continual struggle between the devil and God, again an elaboration of Plato's dualism but with the nuance that there is no conscious charioteer (he argued against the idea of free will).

Modern theories of mind also suggest multiple subsystems, only some parts of which are accessible to conscious thought:

  • Freud offered the first great iteration of the idea that only one of people's two minds is accessible to conscious experience. He called the conscious mind "I" (das ich in German, or ego in Latin) and the non-conscious mind "it" (das es in German, or in Latin id). The idea that the non-conscious mind directs behavior is consistent with Two Minds Theory, although the mechanisms of operation proposed by Freud are not.
  • Cognitive psychologists make a distinction between "hot" and "cool" thoughts, with the temperature metaphor corresponding to the degree of emotion the person is feeling at the time of the thought. There are demonstrable differences between the types of decisions and beliefs people will express in a "hot" emotional state versus a "cool" rational one. Version #1 of the theory diagram (above) shows parallel "hot" and "cool" tracks that mirror Leventhal's dual-process model of health behavior. Our diagram shows the same two paths as Leventhal's, with the lower path focused on emotional reactions and the upper one focused on cognitive representations of events.
  • Behavioral economists have suggested that much of human behavior is determined by non-conscious heuristics and biases. In place of the lists of mental foibles identified by writers in this tradition, our version of Two Minds Theory proposes a single principle of temporal immediacy: questions or behaviors occurring now provoke an intuitive response, while past or future scenarios generate a narrative one. We believe the principle of temporal immediacy can explain many behavioral economics findings.

How is Two Minds Theory Useful?

We hope that Two Minds Theory is useful for helping the science of human behavior to advance. In particular, we hope that it will:

  1. Draw attention to the problem of intention-behavior gaps, which are often glossed over in studies that measure human behavior based on retrospective questionnaires about behavior over a period of time. Results from such questionnaires often agree with results from other surveys about people's attitudes and beliefs (e.g., self-efficacy, health beliefs, intentions). However, they are often quite different from people's actual behaviors when these are measured by observation. Unfortunately, only actual behavior has an impact on health!
  2. Encourage researchers to measure behaviors and intuitive-system processes in real time, and in the context of people's everyday lives. We believe that such ongoing measurements (sometimes called ecological momentary assessment) will produce more accurate and relevant information about the intuitive-level processes that actually produce health behaviors. See the Measures tab for more details.
  3. Promote the development of new health behavior change interventions that are based on modifying the intuitive system or promoting better integration between the intuitive and narrative systems. We hope that these will replace older intervention modalities based on the idea of "willpower" or the idea that people can simply make better choices by using reason to overpower their intuitive responses. See the Interventions tab for more ideas about what forms such Two-Minds interventions might take.
  4. Lead to new scientific findings about health behaviors as they actually occur in context, and based on intuitive-level mental processes. The intuitive system is still largely a black box, and further theory development is needed to explain exactly how it works in specific situations. The role of attention/mindfulness and the iterative relationship between narratives and intuitive reactions over time are two other areas in which further theory development may be helpful. See the Publications tab for our latest work.
  5. Generate new and better understandings of how people behave in everyday life, that can help us to address urgent health problems and societal needs. Remember that the ultimate goal of Two Minds Theory is to answer the question "why do people do anything?" See the Blog page for our ongoing reflections and ideas.