Labelling effect in insects: cue associations influence perceived food value in ants

Humans usually assess things not in terms of absolute value, but relative to reference points. The framing of alternatives can strongly affect human decision-making, leading to different choices depending on the context within which options are presented. Similar reference-point effects have been recently reported in ants, in which foragers show a contrast effect: ants overvalue a medium-quality food source if they were expecting a poor one, and vice versa for expectations of good food. However, studies of human consumer psychology have demonstrated that expectations, for example from product labels, can drive value perception in the other direction via assimilation. For example, an expensive bottle of wine is perceived as more enjoyable compared to a cheaper bottle, even if the wine is the same. In this study, we demonstrate a similar labelling-association effect in an insect: ants showed assimilation effects by spending twice as long drinking at a medium quality food source if it was scented with an odour previously associated with high quality than if it was scented with a poor-quality label. The presence of odour cues in the food during consumption and evaluation is critical, as without them, odour-driven expectations of quality result in contrast, not assimilation effects. The addition of a quality label in the food thus reverses contrast effects and causes value to be aligned with expectations, rather than being contrasted against them. As value judgement is a key element in decision-making, relative value perception strongly influences which option is chosen, and ultimately how choices are made.