The next time your dog happy greets an old friend, remember this: her pup most likely can"t mental the last time lock met.

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We regularly say someone has actually "a memory like an elephant," or, if it"s a forgetful person, "a goldfish." however in comparing our memory with that the animals, what"s the truth? (Read "Animal Minds" in National geographic magazine.)

A recent investigation of short-lived memory suggests animals don"t remember particular events lot at all—instead, they keep away helpful information around what could help them survive.

Covering 25 varieties that ranged from dolphin to bees, the study uncovered the average short-term memory expectations of pets was 27 seconds (which to be the midway suggest before the memory is lost), follow to a team led by Johan Lind, an ethologist in ~ the Centre for the study of social Evolution in ~ Stockholm University, Sweden. (See "Dolphins have Longest memories in animal Kingdom.")

Dogs forget an event within 2 minutes. Chimpanzees, at about 20 seconds, room worse 보다 rats in ~ remembering things, if the memory spans that three other primates—baboons, pig-tailed macaques, and also squirrel monkeys—exceeded just bees (the sole study participant the wasn"t one of two people a mammal or a bird).

Since chimps room our closest life relatives, Lind said he to be surprised by their bad performance. It suggests human capacity for memory progressed after we branched from the many recent common ancestor through chimps, over six million year ago.

Reported in late 2014 in the journal behavioural Processes, the findings drew on data from almost a hundred researches of captive pets that supplied a storage test of recent random occasions known as the delayed matching-to-sample (or DMTS) method.

In this test, an animal is generally shown a visual stimulus such as a red circle. The red circle disappears, then, ~ a delay, it"s displayed again with an additional sample stimulus—a blue square, say. The animal, usually through the impetus of a food reward, has actually to choose the original sample that saw.

Compared with animals, humans uncover this kind of test a breeze—we pick the exactly sample effortlessly after 48 hours or more, studies have shown. (Also watch "A blog post From your Brain: I"m Not great At remembering What ns Hear.")

"The data tell us that pets have no irreversible memory of arbitrarily events," Lind said. Based on the brand-new study, "we think humans" capability to mental arbitrary occasions is unique."

Memories Not created Equal

This capacity is also called episodic memory, and it allows us to remember almost any occurrence, however trivial, for lengthy periods.

"We experience this daily when us remember where we parked the auto or that we have to pay a bill next week," Lind said.

While there space plenty of examples of animals with lengthy memories— elephants never ever forgetting a face, the cat that"s scared of the pet transport after a past visit to the vet, swallows returning to critical summer"s nest—they aren"t using episodic memory, follow to Lind.

Such cases "are as result of associative memories," he says. They"re not based upon "memories of specific events. In the second case, the cat associates the carrier v danger. Together memories are really robust and will continue to be for a lengthy time—even for life—in animals."

That"s because animals may have devoted memory systems hardwired come remember particular "biologically appropriate information" (such as whereby to discover food), the research authors proposed.

Take the example of the western scrub jay, a food-caching bird whose ability to remember and also choose in between its hidden stores has actually been reported as proof of episodic-like memory in animals. (See "Bird-Brained Jays Can arrangement for the Future.")


But, claimed Lind, "if this scrub jays had actually an episodic memory, as humans do, lock would have no problem solving the matching-to-sample experiment."

The scrub jays" performance in the experiment is yes, really no different than that of other birds, however. Your "memory will decay within half a minute," the said. (See pictures of pets that space smarter than you think.)

Mental Time Travel

Scientists view this memory distinction as vital to do the efforts to recognize what mental an abilities we re-superstructure with various other animals and what"s unique about the person mind. (Read about the amazing person memory in National geographical magazine.)

"The examine of episodic storage is crucial, because it is tho under controversy whether other pets can retrieve memories of an individual past occasions in the same way humans do," Gema Martin-Ordas, who research studies animal and human cognition at Newcastle University"s academy of Neuroscience in England, said in one email.

"For example, ns remember that ns went for a operation to the park yesterday, and I to be perfectly mindful that this storage is part of my an individual past experience," stated Martin-Ordas, that wasn"t connected in the brand-new study.

Given our present knowledge, however, "it might be too beforehand to controversy that human beings are the only ones who space able come mentally travel earlier and front in time," she added. (See this interactive: "Mapping memory in 3-D.")

Martin-Ordas"s own research has discovered evidence that an excellent apes execute remember episodic-like details because that days and even years, listed Victoria Templer, a psychologist in ~ Providence university in Rhode Island.

Both researcher urged caution in interpreting the results of the new study.

As the study authors us observed, "some types or people might readjust well to a laboratory environment, and also some may not," Templer said.

For instance, it can be that chimpanzees recollected worse than rats in the DMTS experiments due to the fact that the rats had much more training in the storage task.

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But if the short-term memory spans that chimps and also other primates really space as mediocre as the DMTS test indicate, "the study reminds united state that evolution is not a unidirectional ladder of advancement with humans at the top and apes close behind," Templer said.

That"s something because that us humans to remember—we could not be together smart together we favor to think.