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Preparing for the future has been an integral component of human survival on this planet. From deciding what to eat for lunch to choosing a retirement fund, we engage foresight with great frequency and to great effect. While this extraordinary adaptation has no doubt been a blessing for most of humankind it may nonetheless be a curse to some; those who perpetually envisage a threat filled future replete with agony and discomfort. A recent paper published in the British Journal of Clinical Psychology suggests that the ability to self-generate anxiety via mental scenario building may be a cruel side effect of a previously adaptive threat management system (Miloyan, Bulley, & Suddendorf, 2015).
Anxiety disorders rank highly amongst the most prevalent mental illnesses (Baxter, Scott, Vos, & Whiteford, 2013) and cause significant burden (Weiller, Bisserbe, Maier, & Lecrubier, 1998), yet they may persist today because of a survival or reproductive advantage they conferred to our ancestors. Anxiety, unlike other mental illnesses, is characterised by hypersensitivity to detecting threats (Bateson, Brilot, & Nettle, 2011; Boyer & Liénard, 2006; Brüne, 2006), providing possible benefits in the future.
Other emotions such as fear also prompt responses to danger (Feinstein et al., 2013), but anxiety may prompt individuals to make more extensive preparations for possible future threats. Extreme sensitivity to threats, such as imagining a snake in your boot and taking the precaution to check it out, may confer a survival advantage, despite producing false alarms. Imagine if you will a hominid ancestor hearing a rustle in the nearby undergrowth. At this point, he or she considers two courses of action: ignore the sound based on the assumption that it is not a threat, or flee the area and any possible predator that the bush might be concealing. If there isn’t a predator and the hominid ignores the sound, there is no cost and both the hominid and whatever generated the noise continue their day in peace. If there is in fact a predator rustling around in the bushes, our relaxed hominid may well become breakfast. Take, in contrast, a hyper-vigilant individual constantly assessing the potential to become a snack. This hominid hears the rustling and immediately flees. If the rustling is the result of a harmless bird, the hominid may suffer some cost by leaving (i.e. expended calories or abandoned resources), but for the most part is no worse off than he or she was before abandoning the region. If there is a predator, the hominid has now escaped with their life, free to reproduce and pass on this cautionary trait to little hominid babies. Of course this hominid might experience hypertension or tissue damage due to stress hormones and adrenaline (Brüne, 2008), but this is probably a fair trade for not being eaten.
Of course this hypothetical deals only with present cues of a threat. Anxiety also tends to elicit negative mental predictions about the close and distant future. Miloyan, Bulley, and Suddendorf (2015) posit that the exaggerated anticipation of negative future events could provide an advantage by motivating a higher degree of preparation or avoidance of threats. As evidence, the authors point out that anxiety is typified by negative foresight biases. Anxious individuals are more likely to mentally generate negative future experiences than non-anxious individuals (Hoerger, Quirk, Chapman, & Duberstein, 2012; MacLeod & Byrne, 1996). Surprisingly, anxious individuals aren’t inhibited in their ability to generate, anticipate and expect positive future events (MacLeod & Byrne, 1996; Miranda & Mennin, 2007; Quirk & Martin, 2015; Wenze, Gunthert, & German, 2012). Rather, they tend to overestimate both the duration and intensity of their own emotional response to negative events (Wenze et al., 2012) indicating an impact bias for potential threat-related experiences.
As well as fearful prospection, anxiety leads to rehashing past scenarios in which danger was present (Brown et al., 2013; MacLeod, Tata, Kentish, & Jacobsen, 1997). Further, anxious recollection biases generalizable components of the event over specific details (Brown et al., 2014; Brown et al., 2013). This may allow the flexible application of general information across various, recurrent fitness threats. Various aspects of threat related scenarios could then be adaptively mentally recombined to generate various novel and familiar potential hazards (Schacter & Addis, 2007; Schacter, Buckner, & Addis, 2007; Suddendorf & Corballis, 1997; Suddendorf & Corballis, 2007).
While non-human animals certainly show evidence of experiencing anxiety (Bateson et al., 2011; Bethell, Holmes, MacLarnon, & Semple, 2012; Brilot & Bateson, 2012) humans appear to be unique in our ability to fret about temporally dislocated events. Moreover, humans appear to be the only species able to trigger anxious responses to both consciously and unconsciously generated mental scenarios. Miloyan and his co-authors postulate that this self-generated anxiety is only made possible by our ability to project our minds forward and backwards in time, specifically in regard to encountering threats. By examining the fossil record, researchers have observed the first evidence of such behaviour as recently as 1.7 million years ago. This was indicated by the discovery of carved axes that had been transported by our hominid ancestors, demonstrating foresight of a future in which such a tool might be necessary.
This extraordinary ability to predict future scenarios and relive past events may have granted humans the necessary skills to dominate the planet as we do today. Yet, the other side of this coin is the inescapability of a fearful future with the ghosts of yesterday nipping always at our heels. This may have allowed our forebears to survive in our ancestral environment by preparing for an uncertain future, but it leaves many in the modern world unable to truly live for the very same reasons.
References
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