In the sensory evaluation of foods or drinks, good practice dictates that the type of question being asked will determine both the method of evaluation and the sort of panelist that is required. To analyze the different odours, tastes and textures within a complex food requires considerable training in vocabulary and use of rating scales. One by-product of such analytical training is that the individuals become very sensitive to variations in the intensity of product attributes and, by extension, to differences between samples on these attributes. In effect, trained panelists are good at seeing the signal amid the noise of lots of other product qualities.
In contrast, untrained consumers are
highly variable in their use of sensory terms and their assessment of attribute
intensities. It is not that you can’t ask consumers about product attributes,
but rather that you’ll end up with a highly variable set of numbers if you do.
An implicit assumption has been that because of such variability, consumers are
unlikely to be sensitive to variations between similar products or versions of
products, if those differences are quite subtle.
But what if discrimination isn’t only
about perceptual sensitivity? Students of Signal
Detection Theory (and who isn’t?) will know that decisions are based not
only on perceptual sensitivity but also on one’s criterion – essentially, one’s willingness to report something as
being present or not. This is often referred to as response bias, and signal detection
and discrimination methods measure it independently of sensitivity.
We might want to consider also the reasons
why we might want to discriminate between different products or samples. A few
years ago, my flavourist colleague Leslie Norris and I were sitting in her
kitchen discussing whether or not any improvement could be made in the way that
wineries tested for the presence of cork taint in batches of wine. At that time,
in order to reduce the amount of tainted wine that reached the consumer, highly
trained panels were used because these individuals could be made very sensitive
to the tainting compound TCA (trichloranisole)
through their training. But then we had a shared “aha” moment. Trained panels
were being used to ask a question that was primarily of relevance to consumers.
What if these panels were too sensitive, potentially rejecting batches of wine
that consumers would find perfectly acceptable? The outcome of this was a
method – which we termed the consumer
rejection threshold – that specifically used consumer preference responses [1]. In this case, consumers were, by
definition, sensitive enough, but not too sensitive, to achieve the aim.
More fundamentally, perhaps, recent
research has suggested that consumers might in fact be highly discriminating,
at least partly as a function of not being trained. Analytical panelists become
skilled at ignoring their emotional responses to the samples that they
evaluate, with the (probably correct) assumption that analytical and hedonic
approaches are necessarily antagonistic. If discrimination were purely a
perceptual process then we might argue that removing emotion from the equation
is appropriate.
In fact, a case can be made that ignoring
emotional responses actually impairs discriminative ability. Several studies
over the past decade suggest that engaging and utilizing emotions may be
critical to discrimination. An evaluation procedure known as the authenticity test has sometimes been shown
to be superior to analytical methods at detecting product differences. The
essence of this test is that the emotions of regular consumers of a product are
manipulated by exposing them to a story that has a strong negative implication
for their product. For example, in one study, regular consumers of Danish milk
were told that foreign milk imports might be introduced onto the market [2]. Instead
of being asked to find the different sample or the sample with the highest
level of some property, the consumers are asked to pick the authentic (that is,
Danish) sample. In this case, the milk samples differed according to feed type
and storage time, and the authenticity test revealed that both factors had an
impact on milk flavour.
Why do emotions improve discriminability? One
persuasive argument is that eliciting emotional states allows access to the
otherwise “unconscious”, implicitly learned information about the product that
all regular consumers possess. In other words, we are all experts in respect to
the flavour and other sensory characteristics of our favourite products, even
if we do not possess explicit awareness of such knowledge or a detailed sensory
lexicon [3]. This explanation (also called the mood
as Information hypothesis by social psychologists) proposes that negative
emotions focus attention on deviations from the implicit memory of product
attributes. Negative emotions are necessary because they probably act as
signals that something is wrong. In effect, we monitor our own mood to infer
that there is a problem. In turn, this evokes cognitive effort to search for
causes of the “problem”. It becomes adaptive, therefore, to pay attention to
details. In terms of the authenticity test, it is the unauthentic product that
raises the alarm.
The ability of the authenticity test to
induce emotional arousal and improve discrimination is also consistent with
what we know from psychology and neuroscience about emotion and attention. It
is clear that the brain allocates attention to stimuli as a function of their
emotional significance. Thus, using emotional priming stimuli (a smiley face
will do) in a detection task produces improved detection of very brief neutral
stimuli that follow it. Similarly, emotional facial expressions command
attention much more quickly than other sorts of stimuli, as do stimuli that
have previously been paired with a reward.
Another way of considering the
relationship between emotion and discrimination is to think about the later as
a choice situation. Choices and preferences are intimately linked (see for
example, Taste Matters website or blog, August, 2012: Choosing to like of liking to choose). Making
a discrimination is of course making a choice on some basis. Why pick one thing
over another? If an emotion is crucial to the decision, then the decision has
motivational implications. In some cases, discrimination between alternatives allows
selection that contributes to survival, such as when we choose a high-energy
food over a low energy version.
Invoking a motivational explanation of
discrimination leads to some interesting predictions. It suggests, for example,
that we might be better at discriminating tastes or flavours when we are hungry
…. but only for those substances that are likely to reduce hunger. Cattle, sheep, horses and rabbits select and
eat more of forage cut later in the day, when sugars are highest. We, too,
should be better at discriminating sweet - but not bitter - tastes of different intensities before lunch.
