By IANS
Toronto : Dogs greet their masters with the same warmth after a five-minute absence – or five hours. Does this mean they do not possess a sense of time?
This question led William Roberts of the University of Western Ontario to experiment with rats. And he found that the rodents did keep track of time after discovering a piece of cheese, but without forming memories of its discovery.
These results suggest that episodic-like memory in rats is qualitatively different from human episodic memory, which involves retention of the point in past time when an event occurred.
Findings of the study have been published in the latest issue of the journal Science.
“The rats remember whether they did something, such as hoarded food a few hours or five days ago,” explained Roberts. “The more time that has passed, the weaker the memory may be.
“Rats may learn to follow different courses of action using weak and strong memory traces as cues, thus responding differently depending on how long ago an event occurred. However, they do not remember that the event occurred at a specific point in past time.”
The researchers designed an experiment in which rats visited the ‘arms’ of a maze at different times of day. Some arms contained moderately desirable food pellets, and one arm contained a highly desirable piece of cheese.
Rats were later returned to the maze with the cheese removed on certain trials and with the cheese replaced with a pellet on others. They were tested in three groups, using three varying cues: when, how long ago or when plus how long ago.
“This research,” said Roberts, “supports the theory I introduced that animals are stuck in time, with no sense of time extending into the past or future.”