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Rats know when they’ve forgotten something, just like humans

Rats know when they’ve forgotten something. Rats are aware of what they remember, and behave differently when they can’t remember.

Researcher Victoria Templer and her research team at Providence College, in Rhode Island in America, trained rats to dig through sand to sniff four samples: (1) cinnamon, (2) thyme, (3) paprika or (4) coffee. The rats then had go to a dish smelling of the matching scent. If the rats picked the correct dish, they got a piece of cereal (New Scientist, 14 July 2017).

Rats that chose a dish with the wrong scent received no reward. Rats that went to a fifth, unscented dish received a quarter-piece of the cereal. This meant that when rats forgot what they had smelled in the sand, their best choice was to pick the unscented dish – but only if they knew that they had forgotten the relevant smell.

Nine rats were each tested many times across multiple experiments. In some of these, the unscented dish was not there, forcing the rats to choose a scent even if they couldn’t remember it. Without the unscented option, the rats picked the correct dish 52% of the time.

When the fifth, unscented dish was available, the rats chose the unscented option 20% of the time. In those cases where they chose a scented dish, the rate of picking the right dish increased to 61% of the time – an increase that wouldn’t be expected by chance alone.

Because the rats’ performance improved when the unscented dish was available as an opt-out, Templer says this shows that the rats weren’t simply choosing the unscented dish for no reason. They seem to have known that declaring that they had forgotten the smell would still earn them a small reward.

In further experiments, the research team found that letting the rats sniff the sample twice before choosing a match reduced how often they chose the unscented dish. But making the rats wait longer between sniffing the sample and choosing a match pushed up the number of times they opted out.

People and some primates (apes) have “metamemory” – the ability to know what they remember. However, whether rats have it too had been unclear, and this latest study suggests that they might.

People with Alzheimer’s disease or dementia often don’t realise when they have forgotten something, so a test for metamemory in rats could be useful for rodent studies of these conditions.

Journal reference: Animal Cognition, DOI: 10.1007/s10071-017-1109-3

https://www.newscientist.com/article/2140795-rats-can-tell-when-theyve-forgotten-something-just-like-us/


MARTINA NICOLLS is an international aid and development consultant, and the author of:- Similar But Different in the Animal Kingdom (2017), The Shortness of Life: A Mongolian Lament (2015), Liberia’s Deadest Ends (2012), Bardot’s Comet (2011), Kashmir on a Knife-Edge (2010) and The Sudan Curse (2009).
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