What’s New? Smell and taste memory is tuned to novelty detection
February 2012 - The memory of tastes and smells functions fundamentally differently than visual memory. To better understand the characteristics of memory for food, European Sensory Network researchers have developed experimental designs that are essentially different from the traditional recognition experiments.
Witnesses are often asked whether they can recognize a particular person. When the same person is presented, it is much easier for them to come to a correct decision than when another person is presented. Witnesses have an especially difficult time coming to a decision when that other person has a certain similarity to the original person. In this case, identity, or one-to-one conformity is much easier for the human brain to recognize than is difference.
It is a totally different situation concerning odor and the sense of taste, flavor and texture of food. For instance, when consumers are asked whether a particular yogurt is the same as the one they always have for breakfast, they are often mistaken when the sample is in reality the identical product. But when the yogurt sample is different from the commonly eaten one, they usually recognize the difference immediately. For most people the difference is immediately apparent even when there is only a slight difference between the yogurts. This is a real challenge for food producers, since every product change brings the risk that the change will not be accepted by the consumer. Altering the taste of trusted popular food products is especially disliked by the consumer.
The same or different?
In the past, test subjects were usually asked to memorize specific smells or flavours in order to determine whether the subjects could recognize them in a later session. Since these tasks have little to do with the way a person responds in everyday life, Dutch, Danish, and French researchers around Léri Morin-Audebrand from the INRA in Dijon, France, developed more natural, “real-life” experiments. In six different studies the researchers invited the subjects to a meal. The participants were told that the purpose of the study was to measure the feeling of hunger after the meal, or that the meal had nothing to do with the experiment at hand, and was taking place because the experiment was at an “awkward” time, e.g. before and after the usual lunch hour. Thus, the researchers were able to prevent the participants from consciously trying to remember what they were eating. In the second session the participants were unexpectedly asked whether particular foods – for instance, variants of a dessert custard – were identical to the custard they had eaten at the earlier meal. With this trick the researchers were able to measure the unconscious memory processes.
Although the food variants were only slightly modified from the “original” eaten at the meal, the participants easily perceived these modifications. However, when the same custard was presented, correct answers were on the level of chance guessing. The participants felt much surer of the correctness of their negative decisions. Comparable tests with visual stimuli produce the opposite results.
Efficient warning system
Project leader Léri Morin-Audebrand concludes that, “Food memory is primarily directed towards detecting novelty and change rather than recalling previous experiences.” This makes sense, because in this way odour and flavor memory seem to have the characteristics of an efficient warning system that immediately reacts to novel information.”
It is very probable that the basic difference between the “near” senses (smell, taste, and feel) and the “far” (visual and auditory) senses is that the “near” senses react immediately to danger, whereas the “far” senses take time to identify and react to perceived danger.
Thus, novelty detection seems to play a dominant role in the “near” senses which are involved in such essential activities as breathing and eating. Morin-Audebrand states that, “When these senses register a potential danger, the body is already in contact with the danger and can protect itself only through an immediate reaction, e.g. fleeing from an odour, or immediately spitting out a “bad” tasting piece of food. In these cases there is no time or need for identification. Implicit food memory primarily has a warning function.” With these non-verbal memory processes there is no significant difference between men and women. This was also the case concerning different age groups.
| Three types of memory |
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Neurophysiologists have identified three types of memory that operate in different areas of the brain:
The medial temporal lobe is involved with the unconscious discrimination between known and unknown stimuli. |
Contact:
Sylvie Issanchou
Centre des Sciences du Goût et de l'Alimentation, UMR6265 CNRS, UMR1324 INRA, Université de Bourgogne, Agrosup Dijon
17 rue Sully, BP 86510
F-21065 Dijon cedex
