Increasing saltiness perception through perceptual constancy created by expectation - Dijksterhuis, Boucon, Le Berre (2014) - Article

Nowadays, consumer salt intake is too high. This may result in various health consequences, like lower hypertension, an increased risk of cardiovascular disease and an increase risk of stroke. The World Health Organization (WHO) stated that the reduction of salt intake is likely to have large effects on public health.

The high salt intake may be due to the fact that there’s many hidden salt in processed foods. Food companies are in a dilemma: in the one hand they have to reduce the amount of salt in their products; on the other hand, the products have to stay appealing to consumers.

The studies described in the article focus on investigating the effect of saltiness perception. There are many variables that may influence taste perception; however, top-down effects of expectation may play a large role. There are many ways such a expectation may be developed. For example, a study by Pangborn, Bang and Hansen showed that pink-colored white wine was reported to taste sweeter than the same, uncolored withe wine. In this case, visual perception played a role in the forming of an expectation. Also past experiences may have influence on expectations.

Hypotheses and testing

In the article, two hypothesis were described. The first one states that perceptual expectations from past experiences with similar products could smooth the taste variability in one product. The second hypotheses is that perceptual expectations depend strongly on the first bite taken from a product.

To test the first hypotheses, sandwiches with heterogeneous amounts of salt were compared to sandwiches with the same overall salt concentration. The heterogeneous sandwiches were made in such a way that each mouthful had another level of salt.

To test the second hypotheses, sandwiches with a different salt concentration in the first bite were compared with homogeneous sandwiches.

Participants of the study were 198 German consumers who regularly consume savory sandwiches. They were unaware of the test objective and knew little about the tasting procedure. All of the participants were in good general health: pregnant or breastfeeding women, people with blood pressure issues or people allergic to some kinds of food were excluded.

Four kinds of sandwiches were used, each existing of three different parts. Sandwich A had a salt distribution of 33%-33%-33%; the amount of salt was equally spread along the sandwich. Sandwich B had a salt distribution of 50%-0%-50%. Sandwich C had a distribution of 70%-0%-30% and sandwich D had a distribution of 90%-0%-10%. The average total amount of salt was the same in all of the sandwiches.

The task of the participants was to compare the homogeneous sandwich A with each of the other, heterogeneous sandwiches. Each time, they had to indicate which one was more salty.

Only one participant commented that there was sometimes a difference in saltiness between the bites. The other participants were not aware of the differences in saltiness within one sandwich.

Results

The results showed that the heterogeneous sandwiches were more often indicated as salty than the homogeneous ones. The order in which the sandwiches were displayed, also had effects on saltiness perception: when the heterogeneous sandwich was presented last in the pair, participants tend to perceive them more often as most salty. This may imply a “first bite effect” as described in the second hypotheses, together with a recency effect. The effect of the first bites also implies that expectations on previous experiences can actually smooth out differences within one product.