Many of the foods that we enjoy are unhealthy: high in fat, sugar, and salt, and tend to be low in vitamins. Despite rigorous information campaigns aimed at informing people about the risks associated with such consumption habits, we are generally rather poor at changing our (mostly automatic) consumption behaviours . Recently, Marteau and colleagues  have suggested that one way in which to change our automatic behaviours toward food products may be to change food product design or to somehow alter the environment in which those food products are selected or consumed. While food science and technology has mostly focused on changing the sensory attributes of the food itself, a cognitive neuroscience perspective has also demonstrated the influence that changes to the tableware can have on the taste and flavour of food (see  for a review).
Consumption behaviours can change with the shape of the glass [4, 5], the size of the plateware [6–8], and the size of the cutlery with which a person eats [9, 10]. Consumption behaviours are also affected by what a person hears (see  for a review) as well as by ambient lighting and music [12–14].
The visually estimated size and weight of tools used for eating (hereafter referred to as cutlery) are used to shape the fingers in order to grip the cutlery at a particular location (or affordance point) and with a particular force . Vision and proprioceptive feedback then guide the cutlery, and the food, toward the mouth. As such, the visual as well as tactile and proprioceptive attributes of the cutlery (that is, its colour, size, shape, weight, and texture) are all likely candidates for affecting the multisensory nature of taste and flavour . In the series of experiments to be presented here, the colour, shape, size, and weight of cutlery will be independently altered to verify which of these variables affect flavour perception.
Previous research has demonstrated that the colour of the tableware can affect the flavour of a dish. If a glass has a ‘cold’ colour, a beverage served from it may well be rated as more thirst-quenching [17–19]. The colour of the plateware can also affect the perceived saltiness and sweetness of the food tasted from it [20, 21]. The authors of the latter studies suggested that the effect of colour on taste perception most likely reflects an effect of colour-contrast, which, in terms of the current discussion, refers to the colour of food appearing different as a function of the background colour of the plateware and/or cutlery.
The effect of colour (or colour contrast) on flavour perception and consumption behaviour might be mediated by emotion [22, 23], especially since thoughts of food and emotions activate similar brain areas [24, 25]. As Oberfeld et al. (; p. 807) put it: ‘ if a colour induces a positive mood or emotion […] then the same wine tasted in this positive mood is liked better than when in a negative mood’. Whether the colour is present in the food, the tableware, or in the cutlery itself, it would be expected to have similar effects (though perhaps of a different magnitude) on people’s ratings of the taste/flavour of a food or beverage. However, an emotional response to a colour is not the only possible explanation for how colour might affect flavour.
An alternative explanation is that colour affects taste perception because of previous experience which means that people build up expectations associated with certain colours in certain contexts. If the effects of colour on taste are to be explained in terms of expectations, then coloured tableware might be expected to have different effects as compared to coloured food and drink - that is, context matters. If context is important, then red yoghurt might appear as sweeter (making someone think that they are eating strawberry yoghurt) while red plates might make food taste saltier, for example, if the person has had lots of prior experience of eating sushi from a red plate. Expectations may build up as a result of sensory experience, or, as Maga  has argued, there might be natural associations between colours and tastes that have been learned over the course of evolution (rather than in our own lifetime). Thus, redness may carry with it an expectation of a fruit being ripe and sweet ([27, 28] for a review of how sensory expectations affects hedonic ratings see ) and indeed colour signals the nutrient quality of fruits . Coloured cutlery has probably not been experienced with any regularity, and thus may carry less flavour expectation than coloured food. In Experiment 2, we compared taste when samples were eaten off of coloured cutlery versus when the samples themselves were coloured with food dye. In addition to expectation and emotion moderating the effect that colour has on flavour perception, an alternative interpretation is that sensation transference (for example, ) could cause the sensation of colour in the tableware to be ‘transferred’ to the food, which might then induce specific sensory expectations in a person’s mind.
Sensation transference has been suggested as the likely explanation for how the weight of bowls could affect people’s perception of the food consumed from it [32–34]. Participants perceived ‘more’ of each attribute when holding a heavier porcelain bowl, as compared to a lighter bowl. Piqueras-Fiszman et al. explained that the heaviness of the bowl was ‘transferred’ to the contents (the food) such that the latter was perceived as thicker and denser (hence more expensive and more liked). Would the results have been the same if a plastic bowl had been artificially weighted instead? Since plastic bowls are expected to be light, expectation theory would predict that food tasted from heavier plastic bowls would be rated as less pleasant than the same food tasted from normally light plastic bowls (due to the disconfirmation of expectation).
In Experiment 1, weights were added to plastic cutlery in order to determine whether the food was, as in Piqueras-Fiszman et al. , perceived as more dense/liked (which would support the sensation transference hypothesis) or less dense/liked (supporting the expectation theory). Weights were hidden in the handles of the cutlery so that, upon visual inspection, the spoons were expected to be light. Other than the weight, all other aspects of the spoon were the same (that is, they did not vary in material, which is is important given the results of ). Note that this aspect of the design represents an improvement over previous experiments . We also compared an elaborate, rather expensive, plastic spoon that looked like silverware, to the otherwise simple and cheap plastic spoons. The elaborate spoon, if it were to be mistaken for a ‘real’ spoon might then be expected to be heavier than it actually was. The elaborate spoon might also appear to be more expensive, and that expense might, in turn, be expected to be ‘transferred’ onto the perceived value or other attributes of the food sampled from it. Yoghurt was thus sampled from four different spoons, two large and two small, two of which were artificially weighted, and participants rated the perceived density, expensiveness, and sweetness of the yoghurt and gave the yoghurt an overall hedonic rating.
In Experiment 2, the colour of the cutlery was varied as well as the colour of the food. Spoons were red, blue, green, white, or black; and the yoghurt sampled from the spoons was either naturally white or else artificially coloured pink. This design enabled us to compare well-known effects of food colouring, with as yet unknown effects of coloured cutlery. If the colour of the food affects the perceived taste by affecting the consumer’s mood and/or emotional state, then a given colour would always be expected to exert a similar effect on the consumer. Comparing the results of this experiment with the results of previous research where coloured bowls were used  allowed us to assess the extent to which the effects of colour in tableware are stable across environmental changes.
In Experiment 3, we assessed what effects, if any, the shape of the cutlery might exert on people’s taste perception. Food ratings were compared after participants sampled two kinds of cheese (a young cheddar and a mature/aged cheddar) from four types of cutlery (a fork, a spoon, a knife, or a toothpick - thereby varying both the visual and the oral-somatosensory attributes of the cutlery). Would the cheese be perceived as ‘sharper’ when tasted from a sharp tool? In an as yet unpublished study, Gal et al.  describe how cheddar cheese was reported as sharper when sampled after viewing pointy figures as compared to those who sampled the cheese after viewing rounded images. Gal et al. also reported that the influence of geometric figures on the perception of cheese was mediated by participants’ overall liking for cheese (and thus their prior experience with cheese).
Expectations and experience with eating certain foods from certain pieces of cutlery might mediate the effects of cutlery shape on taste perception. As cheese is often served with toothpicks at cocktail parties, or from a knife in a cheese shop, we wondered whether eating cheese with the aid of these tools would make the cheese appear more expensive or more liked. Following on from Gal et al.’s  research, the participants in Experiment 3 represented two groups of the population: those familiar with the description of cheese as ‘sharp’ and those who were unfamiliar with such a description. Familiarity with this term can then be taken as a rough measure of the level of experience with cheese, or of verbal descriptions of cheese).
We present results from three experiments that independently varied different properties of the cutlery. As the participants in all studies were from the same participant pool, and the protocol was similar across the studies, we can somewhat directly compare across studies and assess the relative importance of cutlery’s weight, size, colour, and shape on consumers responses to the food sampled from it. We measured the perceived sweetness, saltiness, density, sharpness, value, and the overall liking of food sampled from different cutlery, in order to determine which underlying mechanisms (sensation transference, disconfirmation of expectation, or mood/emotion) might be responsible for the effects of tableware on taste perception.