A new study reveals that rats have the ability to link cause and effect such that they can expect, or imagine, something happening even if it isn't.
The findings are important to understanding human reasoning, especially in older adults, as ageing degrades the ability to maintain information about unobserved events, the researchers said.
The recent study draws from long-understood ideas that when a rat (or dog or pigeon) observes one event followed by another, such as a tone followed by food, it forms an association between the events. After the association is formed, whenever the rat hears the tone, it expects food to follow.
The researchers found that once rats observe two events together, it not only forms an association but also an expectation. For example, if two lights occur at the same time, a rat will expect one light to occur whenever the other one does.
But even more remarkably, if researchers cover one of the lights so that the rat cannot see it and then the researchers present the other light, the rats take actions as though the hidden light might be on.
"They maintain an image or expectation that the light is present even though they can't see it," Blaisdell said.
This type of counterfactual reasoning in humans declines in old age, especially when a neurodegenerative disease is involved. Thus, understanding this process is key to informing clinical treatments.