A phantom alternative is an illusory option – it looks real but for some reason is unavailable at the time a decision is made. Phantoms can both help and hinder decision making. In animal ecology, phantom alternatives occur whenever a resource is visible, but unavailable at the time of choice. It may be a frequent phenomenon for nectivorous animals, since they are usually unable to detect the presence of nectar before entering a flower.
Prof. TAN Ken of Xishuangbanna Tropical Botanical Garden (XTBG) and his colleagues investigated the effect of phantom alternatives on feeder preferences in a nectivorous insect, the eastern honey bee, Apis cerana.
The researchers determined the effects of unattractive and attractive phantoms by presenting individual bees with either a binary choice set or a ternary one. The binary choice set contained two feeders that differed strongly in two qualities, but were equally preferred overall (‘option 1’ and ‘option 2’). The ternary choice set contained the same option 1, option 2, and a phantom alternative (an empty feeder that had previously contained a reward). All three feeders and their contents were familiar to the bees.
The researchers predicted that bees, like the majority of humans, would show preference changes after experiencing an attractive phantom, but not after encountering an unattractive phantom. They also determined whether phantoms changed preferences by increasing preference towards the item that was most similar (similarity effect) or least similar (dissimilarity effect) to the phantom.
Honey bees were found to alter their preferences when an unavailable item was added to their choice set, just like humans lured in by items later revealed to be sold out. In the presence of an attractive phantom, bee preferences shifted from a 50/50 split between option 1 and option 2 during the binary trials, to a 100% preference for option 2 after experiencing the attractive phantom. Phantoms consistently changed individual bee preferences in favor of the phantom-similar choice. It showed that the presence of an attractive food source, even if it is unavailable, can influence preference relationships between remaining items in the choice set.
The research results suggested that, as in humans, the phantom decoy effect occurred when bees were confronted with an attractive phantom alternative. Their findings highlighted the importance of considering the potential for phantom effects when studying the foraging behavior (the act of looking or searching for food or provisions) of animals. Since an increase in pollinator visits can result in higher seed set, their results opened up the possibility that by shifting pollinator preferences, empty flowers could have otherwise-unpredicted influences on community composition, plant-pollinator interactions and pollinator behavior.
The study entitled “Phantom alternatives influence food preferences in the eastern honey bee Apis cerana” has been published online in Journal of Animal Ecology.
