The ability to asses the strength of your memories – called metamemory – is a trait well known to us humans. But so far it has been found in only a scant few other animals, with rhesus macaques and chimps able to demonstrate it. This select group of creatures may now have a new member, however, as it appears that the humble rat can recognize when it does and doesn't know something too.
The rodents were tested in a series of experiments, published in Animal Cognition. In the first set of tests, the rats were trained to dig through sand and sniff a particular scent – either coffee, thyme, paprika, or cinnamon – and then match it with a dish of the corresponding scent in order to get a treat. If they got the wrong dish, they ended up empty-handed.
However, if they were unsure or had forgotten what the initial smell was, they could choose a fifth dish that had no scent but would reward them with a quarter of a treat. This meant it was better for the rat to get it right, but if they had forgotten which scent was buried (and more crucially knew that they had forgotten this), it was better for them to pick the unscented choice.
The statistics showed that when the unscented dish was offered to the rats, the rate of them picking the wrong scent dropped by more than chance alone. This suggests they did indeed know when they had forgotten the scent and would instead opt for the unscented choice to get their quarter treat rather than nothing at all.
Following on from this, the team altered the amount of time between when the rats sniffed the first smell and when they had to choose which dish corresponded with it. They found that the longer the wait, the more likely they were to settle on the unscented choice, implying that the delay in time increased the chance that they had forgotten the smell. Not only that, but it was also found that if the rats were allowed to sniff the initial smell twice, it strengthened their memory and the rodents were more likely to match it to the right scent the first time around, even when the unscented option was there.
Previous studies that looked at whether or not rats have a metamemory were mixed, but this latest research seems to suggest that they do. This could in turn lead to better and easier ways to study this cognitive ability in humans, as it means we could use rats as a model to look at how our own minds may function.
[H/T: New Scientist]