Trail-blazing ants show hints of metacognition when seeking food

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I think, therefore I ant sure.

Do they know they don't know? Ants seem to examine their knowledge, a little like humans do when unsure of which route to take.

Tomer Czaczkes and Jürgen Heinze from the University of Regensburg in Germany let black garden ants find food on a T-shaped maze, with the food always in one arm. Then they switched the food to the other arm, creating uncertainty for the ants.

Ants that headed in the wrong direction were less likely to leave a trail for the other ants to follow.

"It makes, sense," says Czaczkes. "You don't want to give your sisters wrong information."

He says this might show that ants can question their own knowledge, a basic facet of higher metacognition - awareness of one's own thoughts - although it doesn't prove this.

If true, these ants would be just the second reported case of an insect showing such advanced cognitive behaviour.

Browsing through our memories and reflecting on their quality and strength, to double check what we know and then make the best decision, is an everyday task for us.

But it has been confirmed only for relatively advanced species, such as mammals and a few birds. Recent research has shown that bees, when faced with a particularly difficult task, simply opt out of doing it - a behaviour that may be interpreted as a form of metacognition.

Now, it seems that ants might be capable of a similar mental feat, despite their tiny and simple brain.

Plagued by doubt

Ants normally rely on chemical trails to tell their sisters of a new food source. But what happens when things change and the food is no longer there?

After finding that the food was not where they expected, the ants laid a stronger chemical trail on their way back to the colony once they found the new food location.

"The problem with these trails, is that they can become outdated, but the ants can't take them away. So the next best thing is to just make a new, stronger trail," Czaczkes says.

This behaviour helps the colony deal with ever-changing environmental conditions by keeping them flexible, says Czaczkes.

But then the team noticed something unexpected. After learning about the new food locations, ants that were about to make an error by entering the arm that no longer contained food, were less likely to deposit pheromones compared with when they were on the right track.

"After finding the new food location once, they still usually think that the food is in the old location - they're just not sure," says Czaczkes.

Exploratory behaviour

According to the authors, one way to explain this is that ants are asking themselves how much they trust their memories. Then if they are not sure about the path, they don't want to tell their sisters to follow them.

Not everyone is convinced by their interpretation.

The visits the ants make to sites with no food may not be errors at all, says Ken Cheng, from Macquarie University in Sydney, Australia. "Ants might have other motives, such as exploring. And when exploring, they might not lay down as much pheromone," he says.

Joachim Zeil, from the Australian National University, also thinks this behaviour could be explained by purely statistical models without evoking cognition.

Czaczkes agrees that alternative explanations are possible. He now hopes to study how ants behave under different levels of uncertainty to pin down the role of metacognition in ant behaviour.

"We don't have a smoking gun just yet for the definite proof of metacognition in ants, but we've got plans to find it," he says.

Journal reference: , DOI: 10.1098/rspb.2015.0679