You are deep in the Amazonian rain forest and there is a rustle behind you that’s coming closer. Guess what your brain is doing at that moment? It’s planning your escape.

We plan our escape the moment we hear an approaching sound but we ignore a crisis that has been looming for decades until it is upon us—and even then we may be tempted to dismiss it. How people respond to risks is intriguing and not always consistent, even if the responses are perfectly understandable in isolation.

Consider first the diffuse risk arising from climate change, which by its very nature challenges most known human cognitive and emotional frailties: It’s largely invisible, stochastic, slow by standard human time scales, and until recently, temporally and geographically distant. Add to that the contested politics and you have a perfect storm of risk-detection failure. Scientific warnings about the looming displacement of millions of people are easily ignored, and evidence that the “fertile crescent”, including Syria, has been gripped by a drought that cannot be explained by natural variability alone, still does not provide a direct causal linkage to the refugee crisis that is currently looming over most of Europe. Accordingly, most of us are reluctant to connect the dots even though displacement and violent conflict are risks that may well increase with climate change.

People do not handle diffuse risks well.

By contrast, humans are easily called to action by immediate “threats”, even if they are not actually threats but simple stimuli, such as harmless sounds, that are moving towards us. Those sounds are known as “looming sounds.” Research on evolution and human behavior has identified the potential advantage to survival that results from our sensitivity to looming sounds. In one study, researchers found that people’s propensity to prematurely judge a looming sound as having “reached” them varied with their physical fitness: people who were unfit showed a greater premature looming bias than the more athletic participants. This result makes perfect sense when combined with the additional fact that looming sounds preferentially activate brain areas that are devoted to motor planning. We plan our escape when we hear a rustle in the bushes coming towards us, and we get ready to run sooner when we are less fit.

People respond rapidly to anything that is perceived as a threat.

We know this response to looming stimuli represents a bias, rather than a generalized difficulty with locating sounds, because people are perfectly accurate at perceiving sounds that disappear into the distance.

A recent article in the Psychonomic Society’s journal Attention, Perception, and Psychophysics explored our sensitivity to looming threats in more detail. Researchers McGuire, Gillath, and Vitevitch focused on the effects of mental resource availability, reasoning that if the looming bias is a “primal” response aimed at survival, similar to quickly pulling your hand away from a hot stove, then it should manifest itself mainly when people are in danger, and it should not be resource dependent—that is, it should arise irrespective of how much cognitive capacity we can spare for threat detection in any given moment.

The procedure is schematized in the figure (credit) below. In the figure, the leftward-pointing arrow represents the movement of the looming sound, induced by fading in and increasing its magnitude. Participants were instructed to indicate by button press when they perceived a sound corresponding to some invisible object to make (imaginary!) contact with them. The box labeled “perceived arrival” refers to the typically-observed point at which people press the button indicating that the sound has arrived. This perceived arrival occurs some distance before the sound actually arrives and that distance, in turn, represents the looming bias.

On each trial, one of three different sounds— approaching, receding, or stationary—was randomly presented for 2 seconds. Each trial terminated when the participant responded.

The crucial manipulation involved “cognitive load”; that is, the extent to which participants were cognitively challenged during performance of the looming task. In one condition, called the low load condition, participants were asked to memorize two digits, which had to be recalled at the end of a block of looming trials. In another condition, the high load condition, participants had to remember 7 digits instead. (Actually, this load was manipulated between blocks of trials but it’s easier to think of them as conditions.) It is easy to imagine how much easier the 2-digit condition is than the 7-digit condition—but what is the effect of that memory load on looming performance?

The main results are shown in the figure below, which reveals that under high cognitive load (7 digits) people respond to the looming stimulus sooner than when load is low (2 digits).

That is, people thought the “object” had “contacted” them earlier under higher load than under low load. Given that all other variables were kept constant, this means that the looming bias was greater under higher cognitive load than lower cognitive load. In other words, the looming bias was triggered despite people being otherwise occupied, in the same way that people remove a hand from a hot stove even when they are doing mental arithmetic or some other demanding task.

How do we know this finding represents a looming bias? The answer is in the figure below, which is for the stationary and receding sounds:

Note how here the differences, if any, between high and low load were reversed. Although those differences were not statistically significant, they clarify that the effect of high cognitive load on premature responding represented a specific looming bias, limited to approaching stimuli, rather than a more general propensity to push a button sooner when you are remembering 7 rather than 2 stimuli.

McGuire and colleagues argued that their results lent support to the “margin-of-safety” hypothesis: As they note, “When participants in our study had fewer cognitive resources, and hence were more vulnerable, or not as capable of handling a potential danger or threat, they exhibited a stronger looming bias.” This result is, of course, entirely consonant with earlier findings that the looming bias was greater for people who are less fit than it was for more athletic individuals.

It appears as though when we get busy, and are therefore psychologically vulnerable, we are even more likely to prepare for and respond to perceived threats.

Article focused on in this post:

McGuire, A. B., Gillath, O., & Vitevitch, M. S. (2016). Effects of mental resource availability on looming task performance. Attention, Perception, & Psychophysics, 78, 107-113. DOI:10.3758/s13414-015-1006-2.