Evolutionary Psychology

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Robert Kurzban

The Evolutionary Psychology Blog

By Robert Kurzban

Robert Kurzban is an Associate Professor at the University of Pennsylvania and author of Why Everyone (Else) Is A Hypocrite. Follow him on Twitter: @rkurzban

Strong Fear

Published 7 May, 2012

What is fear? Roughly, fear is an emotion designed to motivate appropriate behavior, especially escape, when faced with a threat such as a predator or enemy. The explanation for the emotion of fear, then, lies in the fitness benefits of avoiding being killed by enemies or predators and such like. People who got scared and so fled from charging velociraptors left more offspring, on average, than those who didn’t.

Strong Mirth?

Now, as an empirical matter, humans do not show fear responses only to those things that can, in fact, harm them. Take, for instance, the movie Hugo, adored by critics and The People (though I found watching it, frankly, a bit misérable); consider the scene in which a small audience is watching a moving image of an approaching train. The viewers scramble out of the way of the image of the train, even though they know that there is no actual train about to hit them. It appears to come hurtling toward them, and they flee from this appearance. From this and our other everyday experiences, we know that, empirically, humans show fear responses  not only to any number of stimuli that can’t hurt them, but also to stimuli that the people who are fearful know, for sure, can’t hurt them.

So, we might now say that there are two distinguishable phenomena. The first is garden variety fear, which is something like being afraid and having the propensity to flee when there is something in the world that, as a matter of fact, actually poses a threat; the (ultimate) explanation for this “garden variety fear” is the one I indicated above, the fitness benefits of avoiding being killed. Such individuals are just regular “fearful.”

However, movies of trains are not, on this way of speaking, garden variety. We’ll call cases in which people show fear when they can’t, in fact, be harmed by stimuli that only appear to be dangerous as “Strong Fear.” We might put it this way:

Fear, as it is used in evolutionary psychology, differs from Strong Fear because a Garden Variety Fearful individual is only afraid if there are actual benefits from being afraid. Thus, a Fearful individual will never show fear to artificially scary stimuli. In contrast, a person who is Strongly Fearful will be afraid of scary stimuli even when there are no actual benefits from being afraid, and even if the person knows that there are no such benefits.

This might strike some readers as a bit loopy. However, the structure of the argument above is no different from the structure of the argument made in the service of distinguishing Reciprocity from Strong Reciprocity:

Reciprocal altruism, as it is frequently used in evolutionary biology, also differs fundamentally from strong reciprocity because a reciprocal altruist only cooperates if there are future returns from cooperation. Thus a reciprocally altruistic player B will always defect in a sequential one-shot PD. (Fehr et al., 2002, p. 4)

In the quotation directly above, a distinction is being drawn between a garden variety reciprocally altruistic individual – they reciprocate only when there are actual potential downstream benefits – and a strongly reciprocal individual, who, just like the Strongly Fearful individual, will reciprocate even when there are no actual benefits from being reciprocal and knows that there are no such benefits. (Compare this sentence to the parallel sentence above. And we can argue about the claim about the conditions under which reciprocal altruists should be expected to cooperate – which is an important point but also not relevant to my present point – which is only about the distinction being made.)

Once we have this distinction, we can begin to try to explain the empirical phenomenon of Strong Fear. Here are two different explanations. One is the “mismatch” or “big mistake” explanation. This view is familiar to students of evolutionary psychology. Stimuli that match the input conditions of evolved systems evoke the responses for which these systems evolved, even if the link between the stimuli and the reason they were selected  has been broken in modern environments. (See, for instance, Hagen & Hammerstein, 2006). In the past percepts of looming predators reliably correlated with the presence of a looming predator. In modern environments, looming predators can be simulated, breaking this reliable correlation.

Here’s a second sort of explanation. Perhaps there was some reproductive advantage to fleeing from simulacra of things that could cause harm. Again, some readers might find this to be an unusual sort of argument, but again I propose it as a parallel to one actually on offer. Using a similar rhetorical riff to the one I’m favoring here, Price et al. (2007) pointed to the consumption of pornography, a pattern of (unbelievably popular) behavior that carries no obvious benefits. Gintis, replying to this example, wrote that: “the capacity to be motivated by artificial visual material may well be an adaptation.” This explanation is that there were fitness advantages of some type to being motivated by artificial stimuli; getting turned on by porn, according to this view, is functional. Again, the analogous argument here would be that there was some fitness advantage to being afraid of images of things that actually couldn’t hurt the viewer, that people who fled from safe but scary-looking things (somehow) out-reproduced people who did not.

Now, I find this explanation implausible on the face of it, but it is an explanation, though one would want to know what fitness benefits Gintis has in mind when he envisions the advantages to being aroused by pornography.

Of course, these two explanations do not exhaust the range of possible explanations. Perhaps there was some group-wide benefit to people fleeing from images of trains that that led to a between-group selection pressure that more than countered the individual costly behavior of uselessly fleeing harmless stimuli, for example.

In any case, whatever the explanation for Strong Fear, it’s important to bear in mind that the term refers to a phenomenon, a set of observations that people show fear reactions to stimuli that can’t, as a matter of fact, harm them. It is not itself an explanation for anything. Referring to Strong Fear as a model or an explanation for some other set of behaviors would be a mistake (perhaps a “Big Mistake”), confusing the thing to be explained with the explanation for it.

(Left to the student: fear is considered something of an aversive state, yet people spend half a billion dollars to see horror movies. Discuss.)

(Hat tip: Mike McCullough)


Fehr, E., Fischbacher, U., & Gächter, S. (2002). Strong reciprocity, human cooperation and the enforcement of social norms. Human Nature, 13, 1–25

Gintis, H. (2007). Unifying the behavioral sciences II. Behavioral and Brain Sciences, 30, 45-53.

Hagen, E. H., & Hammerstein, P. (2006). Game theory and human evolution: A critique of some recent interpretations of experimental games. Theoretical Population Biology, 69, 339-348.

Price, M. E., Brown, W. M., & Curry, O. S. (2007). The integrative framework for the behavioural sciences has already been discovered, and it is the adaptationist approach. Behavioral and Brain Sciences, 30, 39-40.

Further Reading

Burnham, T., & Phelan, J. (2000). Mean genes: From sex to money to food: Taming our primal instincts. New York, NY: Perseus.

  • p0o9i8u7

    Where are you more likely to find a social environment more conducive to your own evolutionary prospects (mates and support)? In the herd who exhibit group response (possibly a type of Costly Signalling Hypothesis) to false threats, or the unemotional loner who doesn’t flee? Does the consumption of pornography (usually a private matter) lead to more antisocial behaviours, or does it mostly ‘defuse’ the motivation to carry out anti-social acts?

  • http://popsych.org/ Jesse Marczyk

    Fehr et al’s (2002) piece has always been a theoretical mess. One of the largest issue is that their own strong reciprocity model does not even seem to predict that people should cooperate or punish under the conditions created in the lab, as I’ve written about before here: http://popsych.org/?p=95

  • Leif Edward Ottesen Kennair

    Clinically speaking: Strong fear = anxiety (fear response to non-dangerous stimuli), and strongly fearful people probably have high N (Big Five) and an anxiety disorder or two… Strongly reciprocal = dependent personality disorder? I quote from ICD (the European version of DSM, not as good, but available online): F60.7 Dependent Personality Disorder
    Personality disorder characterized by at least 3 of the following :

    (a) encouraging or allowing others to make most of one’s important life decisions;
    (b) subordination of one’s own needs to those of others on whom one is dependent, and undue compliance with their wishes;
    (c) unwillingness to make even reasonable demands on the people one depends on;
    (d) feeling uncomfortable or helpless when alone, because of exaggerated fears of inability to care for oneself;
    (e) preoccupation with fears of being abandoned by a person with whom one has a close relationship, and of being left to care for oneself;
    (f) limited capacity to make everyday decisions without an excessive amount of advice and reassurance from others.”

  • Tim Ketelaar

    Nice post Rob, always good to see a bit of emotion in evolutionary psychology.

    In my mind, Seligman’s (1971) paper in which he demolishes the behaviorist approach to phobia acquisition, provides a nice discussion of this distinction. Seligman refers to these “strong fears” as biologically prepared fears or Phobias, which are distinguished from general wariness responses. So, for Seligman, the distinguishing concepts are Phobias and Fears, with the former being a subset of the latter.

    Phobias, as opposed to garden variety fears have three facets:

    1) they are selective–only a small range of stimuli activate them (Seligman points to most phobias being based upon phylogenetically old sources of danger–think snakes rather than lawnmowers);

    2) ease of acquisition–biologically prepared fears can be acquired often in just one trial (see Mineka & Ohman’s work on fear learning);

    and finally 3) Resistance to extinction–Seligman points out that you typically can’t “think your way out of” a phobia, nor is it easy to remove a biologically prepared fear response with classical conditioning (again see Ohman & Mineka’s excellent empirical work on this).

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