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Evidence for Dual Process Theories

What is the strongest evidence in favour of our stripped-down dual-process theory of moral psychology (see A Dual Process Theory of Ethical Judgement)? Greene (2014) cites many studies. In this section we evaluate three of them, including one involving process dissociation (Conway & Gawronski, 2013). (As a bonus, process dissociation also enables us to revisit the issue of whether emotion influences moral judgement.)

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The first premise of our stripped-down dual process theory of moral psychology (see A Dual Process Theory of Ethical Judgement) is probably the most controversial:

  1. Ethical judgements are explained by a dual-process theory, which distinguishes faster from slower processes.

What is the strongest evidence in favour of this premise? Greene (2014) cites many studies. As always we should not take for granted that Greene’s description of the studies is correct: we need to evaluate them for ourselves (see the step-by-step guide in Moral Intuitions and Emotions: Evaluating the Evidence).

We are looking for evidence in favour of the stripped-down dual process theory together with our selected auxiliary hypothesis:

Auxiliary Assumption: Only the slow process ever flexibly and rapidly takes into account differences in the more distal outcomes of an action (see Dual Process Theory and Auxiliary Hypotheses).

Three Studies and Their Predictions

Here we will consider three of the studies Greene cites. It is important to specify which prediction each study tests (which may not be obvious from the abstract).

  • Suter & Hertwig (2011) — prediction: limiting the time available to make a decision will reduce the influence of distal outcomes.

  • Trémolière & Bonnefon (2014) — prediction: limiting the time available to make a decision will reduce consequentialist responses.1

  • Conway & Gawronski (2013) — prediction: higher cognitive load will reduce the dominance of the more outcome-sensitive process.

What Did They Find and What Are Their Limits?

Suter & Hertwig (2011) is an example of a relatively simply study which provides evidence in favour of the dual process theory plus auxiliary hypothesis.

One limit of this study is that it does not involve any variation in the distal outcomes of actions. This is relevant because the auxiliary hypothesis is about how different processes are differently influenced by distal outcomes.

Although not designed with exactly this in mind, Trémolière & Bonnefon (2014) does observe responses to otherwise similar actions with different distal outcomes. However, the findings are not predicted by the dual process theory and auxiliary hypothesis.2

One limit of both Suter & Hertwig (2011) and Trémolière & Bonnefon (2014) is that they treat responses as either consequentialist or not. These studies are sometimes presented as comparing consequentialist with deontological responses; but this cannot be accurate because failing to respond as a consequentialist would does not make you a deontologist (you may be neither).

Conway & Gawronski (2013) overcome this limit in addition to observing responses to otherwise similar actions with different distal outcomes. It is one of the strongest tests of the stripped-down dual process theory and its auxiliary hypothesis. These authors find, as predicted, that higher cognitive load reduces sensitivity to outcomes while not affecting sensitivity to moral prohibitions (such as on killing).

Conway & Gawronski (2013) are also important because they introduce process dissociation in moral psychology. Although difficult to understand (I attempt to explain the bare minimum you need in the recording), this is a powerful method for testing theories.

Next Steps

Having evaluated some of the evidence in favour of the dual process theory, our next task is to consider evidence against it.

Postscript: The Role of Emotion Again

Conway & Gawronski (2013, p. Experiment 3) may be relevant to evaluating to Huebner, Dwyer, & Hauser (2009, pp. 2–3)’s problem about how (according to them) many studies ‘fail to isolate the precise point at which emotion has a role in our moral psychology’ (see PS: Does emotion influence moral judgment or merely motivate morally relevant action?). For they show that a manipulation of participants’ feelings does not influence how sensitive people are to outcomes but does influence how sensitive they are to moral prohibitions (such as on killing). This is consistent with feelings influencing moral judgement but not what you should predict if you are working from the hypothesis that feelings merely motivate morally relevant action.


automatic : On this course, a process is _automatic_ just if whether or not it occurs is to a significant extent independent of your current task, motivations and intentions. To say that _mindreading is automatic_ is to say that it involves only automatic processes. The term `automatic' has been used in a variety of ways by other authors: see Moors (2014, p. 22) for a one-page overview, Moors & De Houwer (2006) for a detailed theoretical review, or Bargh (1992) for a classic and very readable introduction
cognitively efficient : A process is cognitively efficient to the degree that it does not consume working memory and other scarce cognitive resources.
distal outcome : The outcomes of an action can be partially ordered by the cause-effect relation. For one outcome to be more _distal_ than another is for it to be lower with respect to that partial ordering. To illustrate, if you kick a ball through a window, the window’s breaking is a more distal outcome than the kicking.
dual-process theory : Any theory concerning abilities in a particular domain on which those abilities involve two or more processes which are distinct in this sense: the conditions which influence whether one mindreading process occurs differ from the conditions which influence whether another occurs.
fast : A fast process is one that is to some interesting degree automatic and to some interesting degree cognitively efficient. These processes are also sometimes characterised as able to yield rapid responses.
Since automaticity and cognitive efficiency are matters of degree, it is only strictly correct to identify some processes as faster than others.
The fast-slow distinction has been variously characterised in ways that do not entirely overlap (even individual author have offered differing characterisations at different times; e.g. Kahneman, 2013; Morewedge & Kahneman, 2010; Kahneman & Klein, 2009; Kahneman, 2002): as its advocates stress, it is a rough-and-ready tool, not the basis for a rigorous theory.
outcome : An outcome of an action is a possible or actual state of affairs.
slow : converse of fast.


Bargh, J. A. (1992). The Ecology of Automaticity: Toward Establishing the Conditions Needed to Produce Automatic Processing Effects. The American Journal of Psychology, 105(2), 181–199.
Conway, P., & Gawronski, B. (2013). Deontological and utilitarian inclinations in moral decision making: A process dissociation approach. Journal of Personality and Social Psychology, 104(2), 216–235.
Conway, P., Goldstein-Greenwood, J., Polacek, D., & Greene, J. D. (2018). Sacrificial utilitarian judgments do reflect concern for the greater good: Clarification via process dissociation and the judgments of philosophers. Cognition, 179, 241–265.
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  1. As explained in the lecture recording, this study is associated with a second prediction, which the results appear to disconfirm: limiting the time available to make a decision will reduce sensitivity to outcomes. 

  2. Although the Trémolière & Bonnefon (2014)’s findings may be interpreted as disconfirming a prediction (as Gawronski & Beer, 2017, p. 669 propose), it would be incautious to rely on post hoc reinterpretations of findings.