Highly Sensitive Persons (HSPs) - what are the evolutionary advantages?

HSPs are people who process stimuli like sound, touch and taste more intensely. Anybody who is an HSP must have wondered what were the evolutionary advantages of these traits, as their sensitivity and often shyness are perceived mostly as a burden by the affected people themselves with a lot of the even feeling they suffer from a disorder. According to Elaine Aron, HSPs make up more than 50% of patients in psychotherapy

A recent article in Psychology Today tries to answer this question with a hint towards deeper environmental and social memories. This is little consolations for HSPs, who are often the wallflower at parties, suffer from insomnia or depression and are often social outcasts. Moreover, the article reiterates the claim that there is no connection between ASD (autism spectrum disorder) due to some “fundamental differences”, like the difficulties with social cognition and empathy, which people with ASD struggle with and which HSPs have in abundance. However, people with ASD are just as easily overstimulated as HSPs and show many other common traits, like a disklike of small talk.

In my view, ASD/HSPs are the flip sides of two evolutionary personality profiles, hunters/gatherers, a provisional (more male) and caregiving (more female) one with overlap. Elaine Aron herself does not believe there is a connection between HSP and ASD, but that depends largely on her demarcation of HPS, e.g. she states that HSP men are often perceived as more “feminine” or effeminate.

The patterns between HSPs and people with ASD are remarkably similar, starting with picky eating and frequent tantrums in childhood, to being outcasts and bullied in high school. Being HSP does not only come with high excitability but also bundled with some interesting social traits, such as being, being cautious, highly egalitarian, having a sense of extreme social justice, a preference to socialize with people who do not display status and elevated fear of criticism. These are all traits that are also commonly found in gifted children.

I have argued before that all these highly sensitive physical and social traits served our hunter-gatherer ancestors well in their survival in the wilderness. Early farmers were probably much less socially sensitive (they had to, in order to be successful) as well as physically sensitive, living mostly in villages and having to do hard work from dawn to dusk. Moreover, farmer children could be sure that the food they got was pretty safe, whereas hunter-gatherer children couldn’t always be sure the berries they found were safe to eat.

The most common biological correlate to HSPs I could find was the hormone oxytocin. The oxytocin receptor gene seems to be related to social sensitivity, depression and suicidal ideation.

It has been found that HSPs, like gifted children, are often “orchid children”, i.e. they are often healthier than non-HSP children when in the right environment, but also likely to be depressed and prone to mental (anxiety and depression) as well as physical illness (e.g. allergies and other autoimmune diseases).

One of the most common traits of HSPs is shyness. Shyness is a bit of an evolutionary puzzle as shyness that goes beyond childhood shyness as well as extreme childhood shyness would have been disadvantageous in any community. My personal hypothesis for extreme shyness is that HSPs live mostly in a “farmer” world and their shyness is a protective mechanism against less sensitive social interactions.

To summarize: the evolutionary advantages of HSP traits were adaptations to the hunter-gatherer lifestyle that involved higher levels of alertness (danger, presence of pray, etc.) as well as social sensitivity to  ostracism (probably the worst things that can happen to a member of a hunter-gatherer

band). I am not sure, how much memory for social interactions would have been part of the package. If everyone is egalitarian, there would have been less need for social cognition than in farmer societies who have much more complex patterns of reciprocal interaction. In fact, people with ASD often struggle with remembering names and faces. Forming deeper memories of the environment are much more likey being a part of the deep sensory processing, though. Think, e.g. remembering detailed features of a vast territory or the properties of thousands of plant species. If that seems too abstract, just compare the knowledge of insects of an ASD person with a special interest in insects and that of an average person. The ASD person is even likely to outshine most biology teachers in this area.