Rats Careful Deliberators

Rats, like humans, contemplate problems by carefully weighing the costs and benefits of a situation before making decisions, according to a new study on Wistar rats, a rodent developed for research.

The study is the first to demonstrate that a non-human animal creates a desired ratio, or standard, to decide between options requiring varying levels of effort and that yield different rewards.

A person buying a new car, for example, must weigh the cost and the effort needed to make payments versus the value of the car. Rats, and likely all rodents, do something similar, only under a lot more pressure.

"In its natural habitat, rats are facing the problem that little is under their control, so they are facing various levels and forms of uncertainty all the time," said Ruud van den Bos, who led the research. "For instance, the quality and amount of food items at patches varies over time and between different patches, thus benefits are not always the same."

Van den Bos, a scientist in the Faculty of Veterinary Medicine at Utrecht University in The Netherlands, added, "The amount of energy spent to obtain these different items varies during the different foraging sessions, as sometimes it's cold, sometimes it's hot, sometimes it rains, sometimes sudden obstacles are present after heavy storms, etc."

Van den Bos and his team attempted to duplicate such challenges by manipulating barriers in a T-shaped maze that rats explored. Rats entered at the bottom of the "T," which connected two arms.

At the end of each arm was a chamber filled with treats. One side had a low reward — one sugar pellet — while the other side had three to five sugar pellets.

Rats that wanted the higher rewards had to climb steep barriers. It would be like placing a person's favorite dessert behind a Marines-type training wall that would have to be scaled before the individual could nosh. The researchers varied the size of the barrier and the amount of reward on that side to see how the rodents would react.

At first the rats went for the easy pickings, but when they determined more sweets were available on the other side of the maze, they exerted additional effort, but only after a certain point. When the pain yielded too little gain, they stuck with the tiny treat.

Findings have been accepted for publication in the journal Behavioral Brain Research.

Rats Careful Deliberators