Just like humans, pilot data suggests that ants also dislike "disconfirmed expectations" - getting something they didn't expect. The above figure is from a pilot project - the final results were published in Biology Letters, and can be found here.
Animal consumer behaviour
Understanding consumer behaviour is key to economic success. What makes people value one product over another? Sometimes, how people value or enjoy something is not related to the quality of the product.
Value-neutral expectations alter perceived value
Expectation of quality affect the perceived value of things. But many perceptible attributes of an option do not affect it's quality. Can expectations of value-neutral aspects affect value perception? They certainly can in humans: For example, if you give a group of humans a bitter drink, but tell them it's sweet, they won't like the drink very much. However, if you give a similar group the same drink, but tell them it's bitter, they will like it a lot more. Not liking what you don't expect is called "expectation disconfirmation".
Amazingly, we find exactly the same effect in individual ants - ants receiving food which tastes different from what they expect undervalue that food. This may have large ecological consequences for insects, for example by driving flower constancy in bees.
Effort distorts value perception
We all know that working hard for something makes us value it more - this is sometimes called the 'IKEA effect'. Similar effects have been reported in birds. But would an insect also fall prey to such apparently irrational behaviour? We trained ants to food which requires little or a lot of effort to get, and found that ants consistently preferred the hard-work associated food when given a choice. That this effect of effort distorting value perception is so widespread implies that there is a strong evolutionary pressure behind it. The results of this study were published in the Journal of Comparative Psychology, where it was selected as paper of the year. It is available here.