Do Fish Really Have a Three-Second Memory?

Modern myth would have you believe that goldfish can't remember anything that happened more than three seconds ago and, hence, their lives are filled with the constant excitement of never-before-seen sights and sounds.*

Like the notion that crabs and lobsters don't feel pain, this myth is one I hear a lot at my fish-centric day job and one that has been debunked time and time again. Goldfish and other fish are 1) capable of learning, 2) retaining that information, and 3) recalling and acting on it after an extended period of time. Consider the following:

"¢ Jamie Hyneman from Mythbusters trained his goldfish to recognize color patterns and run an underwater obstacle course. More than a month after initially learning the course, the fish remembered it and completed it easily without Hyneman's prompting or aid.

"¢ Rory Stokes, a 15-year-old student at the Australian Science and Mathematics School, recently conducted an experiment with his pet fish to test their memory.

He took a red Lego block and put it in his fish tank whenever he fed the fish, sprinkling the food around the block. Three weeks into the experiment, the fish were approaching the block and waiting for the food before it even hit the water. During those weeks, the time it took the fish to reach the block went from over a minute to just under five seconds. Then, for six days, Stokes fed the fish without using the block. When he placed the Lego in the tank again, the fish rushed to it in just 4.4 seconds. "They remembered perfectly well," Stokes told the Australian Broadcasting Corporation. "They actually had a time faster than the average of the three feeds before I left."

"¢ A researcher at the Rowland Institute for Science in Massachusetts taught carp to distinguish a John Lee Hooker song from a Bach Oboe concerto. The carp could later categorize pieces they hadn't heard before as classical or blues. The fish also learned to distinguished between simple melodies played backwards and forwards.

"¢ Researchers from the Technion Institute of Technology in Israel played a particular sound when feeding their fish, conditioning them to associate that sound with feeding time (this is called classical conditioning, by the way, and an excellent example of it can be found here). After a month of training, the fish were released into the wild. Five months later, when the fish were fully grown adults, the sound was broadcast over a loudspeaker in the sea and the fish returned.

"¢ In a 2003 study at the School of Psychology at the University of Plymouth, fish were trained to push a lever to earn a food reward. When the lever was fixed to work only for one hour a day, the fish learned to activate it at the correct time and didn't bother with it the rest of the day.

"¢ Fish can learn outside of a laboratory setting and remember more complex routes through a natural environment, too. In a recent study from the University of Minnesota, carp were able to learn the location of a food reward within a few days and would consistently leave their home range at night and in turbid conditions to visit the food reward. The researchers suggest that the carp's memories were aided by olfactory cues and that their initial learning of the route to the food was helped by following the lead of other fish.
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So tell us, fish owners, have your fish ever surprised you with their cognitive abilities? Have you taught your goldfish any tricks?

* I haven't been able to find any info on where or when this fake factoid originated. I believe I first saw it on the bottom of a Snapple cap in the mid-90s. Anyone have any ideas?