Fear of frying

In my last post (July, 2014: A Taste of Emotion), I suggested the possibility that responses to tastes were linked to other emotional responses not merely by association to some third, common factor, but rather that variations in taste responsiveness might be the cause of different degrees of disinhibition (defined as inability to delay gratification) or how much we react to emotion-inducing stimuli of all kinds. Speculation is fine but how do we establish that one thing has caused another? Proving causal links between any two phenomena is always difficult, but we can ask what sort of evidence might make us take an idle speculation more seriously, even in the absence of absolute proof.

My own first question was whether we had any evidence that variation in taste preferences – apparently uniform at birth – emerges relatively early. If it does, then this can potentially be an influence on subsequent emotional development. This search sent me to the bowels of my dusty reprint archives (more strictly, the Endnote^tm program on my computer). The answer is that there is such evidence, at least when we consider sweetness preferences.

The strong preference for sweetness seen at birth starts to decline as the infant reaches the second half of their first year, such that some infants become relatively indifferent to sweetened water [1]. What does increase is variability in response to sweetness and a plausible hypothesis is that this is a consequence of differing exposures to a variety of foods, only some of which are sweet. And there is evidence for this. Infants fed sugar water prior to 6 months maintained a high preference for sweetness in water at 12 and 24 months. In effect, at 2 years of age, these infants were “sweet likers” (see: February, 2013: How sweet it is …. Or is it?). In contrast, those never fed sweet water did not show a strong desire to drink sweetened water over plain water [2]. Hence, one consequence of the practice of feeding infants sugar water is that is maintains the same high preference for sweetness that exists at birth into their second and third years.

Secondly, is there any evidence that taste experiences are linked to other emotions? Again, some of the “side effects’ of sweet tastes suggests that there might be. We know, for example, that sweet tastes can pacify an infant when they are receiving a painful hospital procedure [3]. The mechanism is not exactly certain but is likely to involve the activation of reward/pleasure pathways that inhibit pain. The reason that some mothers administer sugar water is presumably to help pacify their distressed infant. Through such pairings, the infant will learn to associate demands with reward – perhaps a precursor of later inability to inhibit immediate gratification.

But taste hedonics is not the only potential early influence on later emotions. One other obvious food-related candidate that may influence emotional development is food neophobia (FN). When seen in children, typically those aged 2 - 6 years, it is interpreted as an adaptive developmental stage that limits ingestion of unfamiliar, and therefore potentially dangerous, items that might be mistaken for food. It is thought to be mediated by the fear that unknown foods might taste unpleasant [4].

FN varies with a number of different factors (age and education, for example), and can be modified by experience with food variety. It also differs between cultures: in one study, consumers in New Zealand were shown to be on average more FN than a similar group from Japan. Dietary variety, or at least an attitude towards dietary variety, would seem to be the most logical reason for such differences. Nevertheless, FN is a strongly heritable trait [5] that persists into adulthood in substantial proportions of the population – up to 50% in some estimates. 

As in children, high FN adults have low dietary variety and show a reluctance to consider new foods – even if they are simply new versions of something already eaten.  They also dislike larger numbers of foods than their low FN neighbours. For the high FN individual, therefore, eating is associated with either boredom with the limited horizons of their diet or anxiety at the prospect of encountering something unfamiliar (or perhaps both) – in either case, food generates a relatively low level of pleasure compared to that experienced by the rest of us.

If basic tastes such as sweetness and bitterness elicit some of the very earliest post-partum emotions, then pleasure in our early years is clearly also heavily reliant on food. Rewards are often food based – the ice-cream or cake treat – and it is in these early years that children start to associate particular foods with other rewarding experiences, such as a trip to the well-known McDougalls Scottish burger ‘restaurant’ (Slogan: “It could be worse!”). Presumably for the highly FN child or adolescent, there is no such thing as being “pleasantly surprised” by food.

But there are many things about the FN experience that are unknown. How does the development of preferences for new foods develop in high FN individuals? Do high FN diets exclude whole categories of foods? One example might be very spicy or bitter foods, the consumption of which requires tolerance for initially unpleasant qualities (remember that FN is mediated by a fear that something with taste unpleasant). Rozin has suggested that the single most important question that can be asked of someone if you wish to know their food preferences is “what is your culture or ethnic group?”. It may be the follow-up question ought to involve measuring FN.

Strong evidence is lacking for an effect of FN beyond the food domain. However, more general personality traits such as sensation seeking are based on a broad enjoyment of novelty as well as “thrill seeking” in a variety of contexts. On another occasion, Rozin proposed that eating chilli might be a form of benign thrill seeking and so the question remains as to whether early failure to thrill seek with foods may predispose the individual to adopt similar approach when faced with novel experiences in general. 

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1. Schwartz, C., S. Issanchou, and S. Nicklaus, Developmental changes in the acceptance of the five basic tastes in the first year of life. Br J Nutr, 2009. 102(9): p. 1375-85.

2. Beauchamp, G.K. and M. Moran, Acceptance  of sweet and salty tastes in 2-year old children. Appetite, 1984. 5: p. 291-305.

3. Blass, E.M. and L.B. Hoffmeyer, Sucrose as an analgesic for newborn infants. Pediatrics, 1991. 87(2): p. 215-218.

4. Pliner, P., M. Pelchat, and M. Grabski, Reduction of neophobia in humans by exposure to novel foods. Appetite, 1993. 20: p. 111-123.

5. Knaapila, A., et al., Food neophobia shows heritable variation in humans. Physiol. Behav., 2007. 91: p. 573-578.