Researchers at Queen Mary University of London (UK) have shown for the first time that insects, specifically the bumble bee, can decide where to forage based on differences in the duration of visual cues.
The study, published in Biology Letters, shows that bumblebees can be trained to distinguish between long and short flashes of light.
In Morse code, a short flash or “dot” represents the letter “E” and a long flash or “dash” represents the letter “T.” Until now, the ability to distinguish between dots and stripes had only been observed in humans and other vertebrates such as macaques and pigeons.
PhD student Alex Davidson and his supervisor Dr Elisabetta Versace, Senior Lecturer in Psychology at Queen Mary University, led a team investigating this ability in honey bees. They built a special maze to train the bees to find a sugar reward in one of two flashing circles that appeared in long and short flashing periods. For example, short flashes, or “dots,” are associated with sugar, while long flashes, or “stripes,” are associated with bitter substances that bees hate.
In each room of the maze, the location of the “dot” and “dash” stimuli was changed so that the bees were not guided by the spatial reference. After the bees learned to go directly to the flashing circles associated with sugar, they tested them with flashing lights without sugar to see whether the bees’ selection was due to the flashing lights or to the olfactory and visual cues contained in the sugar.
It was clear that bees had learned to discriminate between lights based on their duration, as most of the bees directly arrived at the “correct” flashing light duration that was previously associated with sugar, regardless of the spatial location of the stimulus.
Alex Davidson commented: “We wanted to see if bumblebees would be able to distinguish between these different time periods, and it was very exciting to see them do it.”
“It is remarkable that bees were able to succeed in this task, given that bees do not encounter light stimuli in their natural environment. The fact that bees were able to track the duration of visual stimuli may suggest extended temporal processing abilities that have evolved for a variety of purposes, such as tracking movement in space and communication.”
“Alternatively, this remarkable ability to encode and process time may be a fundamental component of the nervous system, specific to the properties of neurons. Only future research can address this question.”
The neural mechanisms involved in the ability to track time during these durations remain largely unknown. This is because mechanisms discovered to be synchronized with diurnal light cycles (circadian rhythms) and seasonal changes are too slow to explain the ability to distinguish between “stripes” and “dots” of different duration.
Various theories have been proposed suggesting the existence of more than one biological clock. The ability to distinguish between the durations of flashes of light has been discovered in insects, allowing researchers to test different models with these “miniature brains” measuring less than a cubic millimeter.
Elisabetta Versace continues: “Many complex animal behaviors, such as navigation and communication, rely on temporal processing abilities. To unravel the evolution of these abilities, it is important to adopt a broad comparative approach across different species, including insects. Insect processing times demonstrate that complex tasks can be solved with minimal neural substrate. This has implications for the complex cognitive properties of artificial neural networks, which take inspiration from biological intelligence and must seek maximum efficiency to be scalable.”
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