Eye tracking technology as a tool for investigating food choices

Welcome to this lecture about visual attention, eye-tracking and food choice. My Name is Gerrit Hummel and I am a research associate at the department of nutritional psychology here at the University of Hohenheim. Today you will get to know some basic ideas and concepts that show how eye tracking is used in food research and which opportunities arise from this technology. Besides taste and smell, vision is the most important sense that we can rely on when we make decisions regarding food. Thus, visual attention towards food plays a key role when we choose food from a menu, from a buffet, in a supermarket or in a store.

Researchers are for instance interested in the relations between attitudes towards food, eating behavior, eating habits, attractiveness of food, visual attention and food choice

Therefore, typical questions from researchers are: Which influences can have an effect on visual attention? How could visual attention towards food or food stimuli affect food choice? How could visual attention towards food be changed in order to influence food choice and to support a healthy diet? Following Orquin & Mueller Loose one can differentiate between ‘bottom up’ and ‘top down control’ of visual attention. Bottom up control is stimuli driven, And that means that especially attributes of a stimulus can influence or drive attention of an individual. Many studies showed that color, contrast, complexity or even movement of a stimulus has an effect on visual attention.

The more salient a stimulus is the more attention this stimulus normally attracts In contrast ‘top down’ control of visual attention is also called ‘goal driven’ attention. Goal driven attention is related to the individual’s goals or aims. A person who is for example interested in a healthy lifestyle has of course the intention to choose healthy food. As a result, it is more likely that this person is looking at a stimulus that is appropriate to his or her goal. In conclusion this person’s visual attention would be rather attracted by a juicy salad than by a juicy burger Theoretically, we can distinguish between these controls of visual attention. In real life, both appear at the same time and do interact.

Results from many studies suggest that the goal driven attention has stronger effects than the stimulus driven attention. In other words, only if there is almost no goal driven attention, the salience of the stimulus will be the critical factor for visual attention. Until now, we have learnt a lot about visual attention and its meaning and importance in food research. Now we want to have a closer look how visual attention is measured. One way is by observing eye movements. Both, eye movements and visual attention are very strong related to each other. Today we have a lot of high developed technology to measure eye movements (and with them visual attention) towards food.

However, the idea of eye-tracking is not new and reaches back into the nineteenth century. In those days people for example ophthalmologists were interested in the way eyes are moving when an individual is looking at different things or simply reads a text. At that time eye movements were tracked by the observer himself. Nevertheless, some of the most common types of eye movements known today, the so called fixations and saccades have already been identified in these days. Within the timespan of a fixation the eyes fixate a certain point of interest and are almost still.

Basically we can differentiate between the fixation duration which is the time a fixation lasts and the number of fixations, that shows how many times an object has been fixated within a defined period. Both are essential and correlated to each other. In decision making processes there is a strong causal relationship between visual attention and working memory. The so called eye-mind-hypothesis postulated by Just and Carpenter says ‘that there is no appreciable lag between what is being fixated and what is being processed‘. One main interpretation regarding this hypothesis connected to the number of fixations and fixation duration is that both increase with the importance of a fixated object.

Regarding food choice this means that people who are for example in a supermarket would simply more often longer fixate the preferred food than the undesired ones. In contrast to fixations, saccades are rapid eye movements that shift the attention from one point of interest to another. They normally also terminate and alternate with fixations Fixations and saccades can be shown in a scanpath that reflects the eye movements of an individual.A scanpath allows conclusions about visual attention and the sequence of the single fixations and saccade.

In contrast, a heatmap breaks the information down to visual attention as the density of the number of fixations or fixation duration regarding to a point of interest In a further example of a scanpath analysis we will see how purchase behavior relating to food in a supermarket can be illustrated. In this example the participant of a study buys food and has to make a decision which product he or is going to buy. In this video the participant wants to buy cheese. We can recognize fixations at the times where the circle is almost still over a product, and saccades, they are visualized as the red lines between the fixations.

There seems to be no fixed preference and the participant has a look across all kinds and brands of cheese. Different brands, names and even prices are fixated. And in accordance to the eye to mind hypothesis the cheese that has been fixated most often and overall for the longest time has been chosen by the participant We hope you appreciated this short introduction into eye-tracking methods regarding food choice. Thank you for your attention and see you in one of our next lectures. Bye-bye.