杏吧原创

Ants appear to be optimistic when making decisions based on ambiguous information, even more so if they have just had a sweet reward.

This could be a sign that these animals experience something like our emotions, says at the University of Regensburg in Germany. 鈥淭here is no good reason to rule out emotions in invertebrates, and indeed good reasons to think carefully about this,鈥� he says.

An earlier study found that bumblebees show 鈥渆motion-like state changes鈥� in certain laboratory tests, so Czaczkes and his team wanted to see whether the same was true of black garden ants (Lasius niger).

First they trained the ants to associate two distinct odours with a positive outcome 鈥� access to a sugar solution 鈥� or a negative one 鈥� getting a bitter quinine solution or an electric shock. Then the ants were placed in a maze where they had a choice of two paths: one with a mixture of the two odours and one with no scent.

Around two-thirds of the ants chose an equal parts mixture of the two odours over the odourless option. 鈥淚n an ambiguous situation, the ant acted as if it expected a reward,鈥� says Czaczkes. 鈥淒oes this mean it experiences a subjective hopeful feeling?鈥�

When the ants were given a sugar solution at the start of the maze, they were even more likely to choose the mixed odour. 鈥淭his could be the ants becoming even more optimistic, possibly because they are happy,鈥� says Czaczkes.

However, we can鈥檛 tell what the ants are really feeling 鈥� they might behave this way because they have simply updated their estimate of the probability of finding food, he says.

This study is exciting because it shows us that the origins of mental states such as optimism might be simple circuits, says at the University of Sussex in the UK. 鈥淚t鈥檚 nice that you can demonstrate that the changing balance of basic memories can lead to sophisticated decision making which could be described as optimism,鈥� he says.

This study adds to a growing body of evidence that insects conduct more sophisticated cognition than once thought. 鈥淚nvertebrates experience the world in ways which are often very similar to how we experience it,鈥� says Czaczkes.

Graham, however, is wary of drawing comparisons with humans. 鈥淲e have a much more complex set of memories active across all realms of our lives over much longer time,鈥� he says. 鈥淚t鈥檚 orders of magnitude more complex.鈥�

Reference: bioRxiv, DOI: