Most of us have no trouble naming the foods we like most, or indeed saying how much we like them. We may not use a rating scale to do this, but can still convey that we like chocolate cake “a lot” or even – perhaps to confuse non-English speakers – “an awful lot”. But making a general statement about liking for foods (or anything else) carries with it a couple of important assumptions. The first of these relates to context (doesn’t everything?): chocolate cake is great in the evening as a dessert, but perhaps less enjoyable first thing in the morning. This is why we can say that we like chocolate cake more than we do cornflakes, but at the same time also say that we prefer the cornflakes if we are talking about breakfast.
Secondly, though, and much less obviously, I could ask you about your love of chocolate cake in relation to past or current consumption of it. Thus, being hungry and faced with the prospect of your first bite of the slice in front of you, your answer is pretty obvious. Ok, then what about after your first bite? After your second bite? Third? Tenth? There is a well-known phenomenon called sensory-specific satiety (SSS) that kicks in once we start to eat. This refers to the fact that simple exposure to the sensory properties of a food – its taste, smell, texture – causes the food to become less liked.
The effect of SSS isn’t enormous – we see no more than about a 20% reduction in liking if we measure it using rating scales. But it seems to be enough to motivate us to want to eat other foods that are available instead. Hence, the theory behind SSS is that it is an adaptation that helps maintain a varied diet. It is apparently also important in telling us when to stop eating. In studies that allowed participants to consume as much food as they wanted, the reason ‘I just got tired of eating that food’ was found to be just as common a reason for stopping eating as ‘feeling full’.
The distinction between these reasons is important: SSS is not about being full. Even chewing a food and not swallowing it will produce a decrease in liking for that food. Nor is it about nutrients – SSS occurs between foods that are similar in their flavours, but not between foods that are similar in nutrient content, but not flavour. So, we get bored with exposure to flavours and, indeed, pretty much any aspect of the food. Repeatedly eat red M&Ms and you’ll soon find the blue ones becoming strangely more appealing. Chew on something quite elastic for a while (say, a caramel) and you’ll start to long for a little bit of crispness.
Becoming bored with eating the same food repeatedly is not news, of course. With the exception of breakfast, where many people trade off boredom for convenience, having the same meal over and over again on successive days leads to both loss of pleasure and reduced consumption. It is not a surprise that many diets use boredom as a way pushing the dieter to eat less and hence loose weight. Whether over the short term, within a meal (SSS) or over days or weeks (boredom/monotony), we eat more when confronted with foods that are varied in the flavours or textures.
But what if you didn’t recall what you’d recently eaten? In an earlier post (February, 2012: Remembrance of foods past), I wrote about the dramatic case of a severely amnesic man who ate three full lunches over the space of little more than an hour with apparent gusto. Clearly, in his case, the inability to recall what he’d eaten allowed him to maintain an interest in eating.
A recent study suggests that, for all of us, memory and attention play a crucial role in determining the degree of pleasure we derive from food, and hence how much we are likely to consume. Larson and colleagues [1] asked study participants to view pictures of either sweet or salty foods and rate how appetizing they thought those foods were. The idea was that in making these ratings, the participants were implicitly retrieving experience of those foods from memory. All participants were then asked to eat some salty peanuts and rate how enjoyable these were. If the participants had rated only 20 food pictures, then there was no effect on enjoyment of whether the pictures were of sweet or salty foods. However, after 60 pictures, those who had previously evaluated salty food pictures enjoyed the peanuts much less than those who evaluated sweet food pictures. What was producing this effect? In a subsequent study, the researchers included a condition in which participants were asked only to evaluate the brightness of the food picture and not how appetizing the food in the picture was, and this produced no such effect. As a result, the authors concluded that attending to the food sensory qualities (sweetness or saltiness) and retrieving information from memory was the source of this effect.
This study has a number of crucial implications. The first of these is that it provides evidence of the cross-modal nature of SSS, in that a picture, when allowed to activate prior experiences, could reduce enjoyment of an actual food flavour. We know that different aspects of foods (tastes, odours, textures) are bound together in memory as flavours, and that experiencing one aspect such as an odour can elicit the food’s taste qualities and any positive (sweet) or negative (bitter) qualities the taste may have [2]. This study points to a similar integration of visual and taste/odour food properties, also with hedonic consequences.
Secondly, these authors suggest that such effects may be in operation when we view advertising or other cues to foods, if these cues cause us to imagine the experience of the food based on our memory. That is, rehearsing the experience of a food in response to a cue will cause us to experience less enjoyment of the food itself and potentially to reduce the amount eaten. If true, this runs contrary to what we know about the effect of environmental cues, which are known to trigger eating [3]. This apparent paradox may be due to the fact that those affected by cues most are those suffering from hedonic hunger – that is, those who have deprived themselves of highly palatable foods. In their case, relative lack of recent memory for such foods may be the issue.
One final implication of this study concerns the phenomenon of mindless eating (see February, 2012: Unaware eating), in which attention diverted from eating – for example, by watching TV – leads to higher consumption. The Larson study suggests that it is possible that paying attention to food while we are eating is necessary for SSS to occur because it requires access to prior memories. Perhaps we therefore experience less SSS with novel foods, for which we have no memories?
____________________________________________________
1. Larson, J.S., J.P. Redden, and R.S. Elder, Satiation from sensory simulation: Evaluating foods decreases enjoyment of similar foods. Journal of Consumer Psychology, 2014. 24(2): p. 188-194.
2. Prescott, J. and R.J. Stevenson, Chemosensory Integration and the Perception of Flavor., in Handbook of Olfaction & Gustation: Modern Perspectives., R.L. Doty, Editor. 2015. p. 1008-1028.
3. Fedoroff, I., J. Polivy, and C.P. Herman, The specificity of restrained versus unrestrained eaters’ responses to food cues: general desire to eat, or craving for the cued food? Appetite, 2003. 41: p. 7-13.
