Why some people jump... and others don't, while watching horror movies

HALLOWEEN is nearly upon us, and if you’re anything like me that brings one thing in particular to mind – horror movies.

There’s something counter-intuitive about the Halloween horror movie experience. Nobody likes to be really scared, nobody wants to be in the presence of an axe-wielding psychopath, but movies give us a chance to experience a shadow of that terror vicariously – no need for the real thing. 

And there are arguably few more delicious aspects of a horror movie than being so on edge that we jump several centimetres clear of the chair at the slightest unexpected touch or sound.

That uncontrolled leap, that alarmed jump, has a specific name in scientific terms – the ‘startle reflex’. It seems to be something that happens automatically, and has presumably been selected in the evolutionary process as it serves a useful purpose. It appears to help us to mobilise to defend ourselves against threat. As we know from experience, the startle interrupts us in whatever we’re doing, allowing us to pay attention to the threat; and it’s also associated with increased heart rate and blood pressure - typical of our body’s ‘fear, fight, or flight’ response to stress.

Of course we are prone to startle at all times, but the effect becomes more pronounced when we have been exposed to unpleasant stimuli - a phenomenon called ‘aversive startle potentiation’ (ASP), and found in both humans and animals. This is further evidence of this being useful in the process of evolution - if it is found in multiple mammalian species, for example, this is probably because it was linked to improved survival all the way back when we had a common ancestor.

Neurophysiological research shows that a part of the brain called the amygdala is also active during the startle reflex. The amygdala is associated with fear, and it is believed that reduced ASP is linked to reduced amygdala activity - and so to reduced fear.

I earlier referred to the “uncontrolled” jump when we are startled. Naturally, however, when people pay attention to not showing fear when watching a horror (and we all know these people - we might number ourselves among them) they can successfully suppress the startle. It’s like an adult version of my 11-year-old son and his friends buying the sourest sweets in the shop, and chewing them with a smile while suppressing the winces and shudders. But equally naturally, some people just don’t exhibit much of a startle reflex at all. Why?

Well, this brings me back to a word I used earlier when discussing horror films – “psychopath”. it’s a word often thrown around, but in psychology we use it carefully and with specific meaning. It’s important to note, by the way, thus while axe wielding types may well be psychopaths, the vast majority of psychopaths are not wielding axes!

One commonly used model of understanding psychopathy is the ‘triarchic model’ - this approach suggests that psychopathy isn’t a straight either/or, but that it is characterised by levels of three dimensions of personality - so psychopathy can be present in different people in different ways.

The three dimensions are boldness, meanness, and disinhibition. Boldness is related to remaining calm in ostensibly threatening situations and a lack of anxiety; meanness is a lack of empathy for, and a preparedness to exploit and manipulate, others; and disinhibition reflects poor impulse control and poor control of emotion. When we consider these features, it seems likely that boldness (with its low anxiety at times of stress) and meanness (with its indifference or insensitivity to the emotions of others) would be linked to people not being affected by the terror experienced by movie characters, and not being scared or alarmed by unexpected noise or touch.

And so it turns out. A recent systematic review of the research, by Sofi Oskarsson of Örebro University in Sweden and her colleagues, found robust evidence that psychopathic personality is linked to lower ASP, but that this is particularly the case for high boldness and meanness.

This is not a foolproof way of identifying people with psychopathic personalities - there is a lot of variation between humans. But if your Halloween horror couchmate doesn’t jump when the doorbell rings for pizza delivery, maybe…