January 06, 2004

The Price of Neophobia

S. A. Cavigelli and M. K. McClintock, Fear of novelty in infant rats predicts adult corticosterone dynamics and an early death, PNAS, December 23, 2003 vol. 100 no. 26 1613116136

Some individuals react to novelty with fear ("neophobes"), others accept or gladly embrace it ("neophiles"). But any living being will encounter novel things across life, and hence the neophobes will be stressed. The Cavigelli & McClintock paper studies the effect of being neophobic on lifespan in rat, and found that neophobes have shorter lifespans than neophile relatives.

In the paper rats were placed in a novel environment and allowed to explore. Rats that did not explore much were labelled as neophobes (and often showed signs of fearfulness). Neophobia is believed to be linked to increase of activity in the amygdala and the hypothalamic-pituitary-adrenal axis: a release of glucocorticoids (the long-term stress hormones cortisol and corticosterone). The neophobic rats also showed higher and more long-lasting levels of stress hormones after the novel experience.

As everybody knows, long-term stress is bad for health. It decreases the immune defenses, it makes hippocampus shrink and in general weakens the body (the rapid response fight-or-flight stress mediated by adrenaline is more OK). And indeed, the neophobic rats died on average younger than the neophilic rats. Their lifespan was 20% shorter, and their mortality was always 60% higher. Being a neophobic seems to stress you to an early grave.

While this sounds like a wonderful argument for us neophiles to use to convince neophobes to come out of their hiding places and embrace the future, there is a problem here. Because the neophobia discussed here appears to develop at a very early age and be a persistent personality factor. It is not just something you decide to throw off.

In the rats it was found that testing young rats for neophobia could be used to predict their neophobia and hormone levels as adults; neophilia and neophobia appears to be rather stable traits that do not change. The same seems to be true in humans: neophobic children grow up into neophobic adults. The origin may be natural genetic variations, but other factors are clearly important. Among the rats pairs of brothers exhibited different levels of neophobia despite their close relation (especially since lab rats are rather similar genetically from the start). Instead early environment and experiences likely play a large role. In the same issue of PNAS there was another paper:

Gerd Poeggel, Carina Helmeke, Andreas Abraham, Tina Schwabe, Patricia Friedrich and Katharina Braun, Juvenile emotional experience alters synaptic composition in the rodent cortex, hippocampus, and lateral amygdala , PNAS, December 23, 2003 vol. 100 no. 26 16137-16142

that showed how repeated separation of degu (Octodon degus, or "brush tail rat") from their parent led to distinct changes in the synaptic connections in the limbic system of their brains - exactly the system that is likely to influence emotional and stress levels. Of course, there are many, many, many, many other studies that have shown that a bad upbringing with little contact with the mother or siblings produce a more "highly strung" individual, be it a rat or a human.

As an aside, I also found a paper about food neophobia in girls (the unwillingness to try new kinds of food):

Amy T. Galloway, Yoona Lee, Leann L. Birch, Predictors and consequences of food neophobia and pickiness in young girls, J Am Diet Assoc. 2003 Jun;103(6):692-8.

that saw a definite correlation between food neophobia and anxiety. Of course, there are many other factors (such as mothers with food neophobia). Also of interest was the negative correlation between pickiness (being unwilling to eat familiar food) and being breast-fed; a bit surprisingly there was no such link between being well breast fed and lack of neophobia. But as usual, psychological data seldom fit neat schemes.

As humans we have a lot more self-regulation options than rats. We are amazingly able to re-train our reactions. But that still does not make us able to easily overcome core personality factors, at least not through direct psychological means. It is an interesting question whether we can deal with this kind of self-limiting personality trait through medication. It would seem that it should not be that hard to lower stress hormone levels chemically, and by reducing that feedback neophobia might be ameliorated (if anything, the health damage could be limited even if the personality remained the same).

But in the meantime it is probably a good idea to hug one's children and make sure they get to enjoy science fiction.

Posted by Anders at January 6, 2004 01:33 PM