Amazing stuff!
"Researchers ... have shown for the first time that an insect—the bumblebee Bombus terrestris—can decide where to forage for food based on different durations of visual cues. ..."
"... In Morse code, a short duration flash or ‘dot’ denotes a letter ‘E’ and a long duration flash, or ‘dash’, means letter ‘T’. Until now, the ability to discriminate between ‘dot’ and ‘dash’ has been seen only in humans and other vertebrates such as macaques or pigeons. ...
They built a special maze to train individual bees to find a sugar reward at one of two flashing circles, shown with either a long or short flash duration. For instance, when the short flash, or ‘dot’, was associated with sugar, then the long flash, or ‘dash’, was instead associated with a bitter substance that bees dislike.
At each room in the maze, the position of the ‘dot’ and ‘dash’ stimulus was changed, so that bees could not rely on spatial cues to orient their choices. After bees learned to go straight to the flashing circle paired with the sugar, they were tested with flashing lights but no sugar present, to check whether bees’ choices were driven by the flashing light, rather than by olfactory or visual cues present in the sugar.
It was clear the bees had learnt to tell the light apart based on their duration, as most of them went straight to the ‘correct’ flashing light duration previously associated with sugar, irrespective of spatial location of the stimulus.
Bees showed "remarkable" ability to learn light patterns ...
“Since bees don’t encounter flashing stimuli in their natural environment, it’s remarkable that they could succeed at this task. The fact that they could track the duration of visual stimuli might suggest an extension of a time processing capacity that has evolved for different purposes, such as keeping track of movement in space or communication.
“Alternatively, this surprising ability to encode and process time duration might be a fundamental component of the nervous system that is intrinsic in the properties of neurons. Only further research will be able to address this issue.”
The neural mechanisms involved in the ability to keep track of time for these durations remain mostly unknown, as the mechanisms discovered for entraining with the daylight cycle (circadian rhythms) and seasonal changes are too slow to explain the ability to differentiate between a ‘dash’ and a ‘dot’ with different duration. ..."
From the abstract:
"The ability to process temporal information is crucial for animal activities like foraging, mating and predator avoidance. While circadian rhythms have been extensively studied, there is limited knowledge regarding how insects process durations in the range of seconds and sub-seconds.
We aimed to assess bumblebees’ (Bombus terrestris) ability to differentiate the durations of flashing lights in a free-foraging task. Bees were trained to associate either the long- or short-duration stimulus with a sugar reward versus an unpalatable solution until reaching a criterion and then tested without sucrose solution with the same stimuli.
In experiment 1, we tested the ability to discriminate between a long stimulus (2.5 or 5 s) versus a short stimulus (0.5 or 1 s). The bees learned to discriminate between the two stimuli.
To check whether bees solved the task without using the absolute difference in proximal stimulation as a cue, we ran a second experiment.
In experiment 2, the flashing stimuli were presented for the same total amount of time in a cycle. Bees could discriminate between durations when the amount of stimulation in each presentation cycle was the same.
This shows general learning abilities in bumblebees, that can discriminate second/sub-second intervals in visual flashing stimuli."
Bees learn to read simple ‘Morse code’ (original news release)
Fig. 1 Experimental apparatus and temporal patterns of light stimuli.
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