A new study published in the journal Current Biology recently found that octopuses can learn how to use mirrors to locate food hidden from view in an impressive feat of spatial thinking never before observed in invertebrates.
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Researchers from Dartmouth College conducted an experiment involving three California two-spot octopuses (Octopus bimaculoides) – the goal was to find out whether the animals could be trained in using a mirror to locate an out-of-sight food source.
“We don’t enter the world knowing how to use a mirror but learn how to use a mirror,” said cognitive neuroscientist and professor at Dartmouth, Peter Tse. “Octopuses can also learn how to use a mirror to infer where things are in the world.”
During the first mirror-use training trial, all the octopuses moved toward the reflection of prey first – it took around 10-12 trials per animal to learn to approach the actual crab instead of its reflection.
Then, once the octopuses were familiar with the mirror, the testing began. Steps were taken to account for the octopuses’ ability to smell and taste through touch – instead of real prey, virtual images of crabs were used.
Each octopus was placed inside a box open at the front and top, with a mirror positioned directly in front of them. The virtual crab was positioned behind the octopus, visible only through the mirror. To receive a reward (an actual live crab), the octopus had to recognize where the crab was located and move towards it.
The animals successfully chose the right location in 73 per cent of the trial, even though the learning and testing tasks were quite different. During training, the octopuses only needed to make a 90° turn near the mirror. During testing, they had to leave the starting area, make a 180° turn, and either move to the back of the tank or climb over the wall of the start chamber.
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Despite these changes, all three octopuses succeeded on their very first test. This suggests they understood the spatial relationship shown in the mirror, rather than just memorising visual cues linked to a reward.
The researchers emphasised how these findings may influence the way we understand how intelligence evolves.
“Octopuses are among the most evolutionary distant animals from humans, as our last common ancestor was a worm that lived 350 to 500 million years ago,” said Mary Kieseler, one of the researchers. “Given that such a remote organism has independently evolved the means to use a mirror as a tool to process spatial cognition suggests that the underlying cognitive processes might be subject to convergent evolution, where different species evolve similar neural solutions to the same challenge."
Using mirrors to locate otherwise not visible objects is a form of mediated perception and is even seen by some as a precursor to self-recognition.
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“Hunters are very effective when they have a mental map of their territory, so that they know where they are in relation to their environments,” added Tse. “Our work suggests that octopuses might also have internal maps, an internal representation of space.”
More research is needed to determine whether they learned through simple associations or by using an internal map of space.
Read the full findings here.
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Top image: Octopus vulgaris. Credit: aurigadesign/Getty Images
