How expectations affect value perception in an invertebrate
Felix Benjamin Oberhauser, Felix Benjamin Oberhauser , Tomer J. Czaczkes
Department of Zoology, University of Regensburg, Germany; Department of Zoology, University of Regensburg, Germany ; Department of Zoology, University of Regensburg, Germany
To make sensible decisions, both humans and other animals must compare the available options against a reference point – either the other options or some previous experience. Options which are of higher quality than the reference are considered good value. However, many perceptible attributes of options are value-neutral. For example, a flower may be blue or red, without affecting the sweetness of its nectar. Such value-neutral differences may be part of an expectation (“I was expecting a blue flower”), but can a mismatch between expectation and experience of value-neutral attributes affect perceived value? To test this, we manipulated a value-neutral aspect of a food source – its taste – while keeping its absolute value – its sweetness – the same. Individual ants (Lasius niger) were allowed onto a runway with a 1M sucrose droplet flavoured either with lemon or rosemary at the end. After the ant made 3 successive visits to a droplet of the same flavour, we switched the flavour in the last, 4th, visit to induce a disconfirmation of expectations. In control trials ants received the same flavour of food on all 4 visits. We found that ants which found a food source whose flavour differed from their expectations laid significantly less pheromone on the way back to the nest, and showed significantly lower food acceptance, even though the molarity of the food was unchanged. As ants recruit other ants via pheromone depositions, a decrease in depositions indicates that the ants value the food less. This implies that the expectation of value-neutral attributes can influence the perceived value of a resource. Such influences of value-neutral variables on value perception may strongly affect how animals interact with, and exploit, their environment, and may explain phenomena such as flower constancy in bees.