Designed by Di. A chatterbox
Rumor: On the Internet, there is a passage widely circulated: "As early as a long time ago, someone told me that the memory of a fish is only 7 seconds. After 7 seconds, it won't remember the past, and everything will be a new beginning. Therefore, in that small fish tank, it will never feel bored. " There is nothing wrong with simply treating this passage as a fairy tale, but many people regard it as a scientific fact. On many Q&A websites, there are questions about whether this passage is scientific. [ 1][2]
Truth: In fact, if "the memory of fish has seven seconds" is taken as a scientific conclusion, many questions will arise. Can memory be accurate to the second? If the average memory of fish is 7 seconds, then some stupid fish only have 2 or 3 seconds. When these "stupid" fish take a bite of food, will they forget what's in their mouths instantly?
Fortunately, fish, as an early vertebrate species, has a very unique evolutionary position, so there are many scientific studies on fish memory. Although the types of fish used as experimental materials are different, the experimental methods and specific purposes are also different, almost all studies on fish memory show that fish memory is far more than 7 seconds.
Experimental evidence, yes.
As early as the 1960s, when chemistry began to intervene in neurobiology, people had studied the memory ability of goldfish. 1965, researchers at the university of Michigan made an experiment with goldfish. They put the goldfish in a long fish tank and then shoot a light at one end of the fish tank. Twenty seconds later, they released an electric shock at the end of the fish tank that emitted light. Soon, the goldfish formed a memory of electric shock. When they see the light, they quickly swim to the other end of the fish tank before the electric shock is released into the water to avoid the electric shock. The scientists who designed the experiment found that through reasonable training, these goldfish can remember the skills of avoiding electric shock for as long as 1 month. [3]
Besides goldfish, another famous ornamental fish-paradise fish-also has a strong memory. When the fish meets a strange goldfish in the pool, it will swim around curiously and look at the new strange neighbor until it loses interest. If the paradise fish and goldfish meet for the second time in the water tank, they will soon find that they are old acquaintances and lose interest in exploration. Experiments have found that this memory can last at least 3 months. [4]
Soon, scientists found that zebrafish, a model organism in biological research, is also a very smart animal, which can complete various tasks. In 2002, several researchers from the University of Toledo, Ohio, tested the memory ability of zebrafish. During the training, they will give zebra fish a red light as a signal before feeding. After 10 days of training suspension, zebrafish still remembers the red light signal indicating that it is time to eat [5]. In the laboratory, zebrafish can also quickly learn how to walk a maze [6], find food according to sound signals [5], remember the shape of predators, and avoid electric shocks according to tips.
Interestingly, zebrafish and humans have similar memory characteristics. For these small fish, too much pressure will make them unable to remember things [7], and distraction will also reduce learning efficiency [8]. The memory ability of zebrafish will also gradually decline with age.
Long-term memory is not impossible.
So, will fish have a stronger memory, such as remembering one thing for several years? Related academic research is very limited, because many kinds of fish can't live that long, and a few years is really too long for a graduate student who is eager to publish a paper. However, there are also some unofficial observations that some fish may indeed have long-term memories.
Charles W. Eriksen, a psychology professor at the University of Illinois at Urbana-Champaign, once noticed that his neighbor always shook the jar with fish food before feeding the fish. After hearing the fish food shaking in the jar, the fish in the pond gathered from all directions to get ready to eat. Inspired by this phenomenon, Eriksson decided to do a fairly simple exercise. He keeps some catfish in his fish pond. Every time he feeds the fish, Eriksson shouts "Fish! Fish! " (Fish-Fish). After several months of training, whenever Eriksson shouts, there will always be 19 catfish swimming to him. The next summer, Eriksson repeated the process. This time, 16 fish obeyed his command.
It was five years when Eriksson returned to his fish pond again. However, he still decided to test whether his catfish still retains its previous memory. So Eriksson came to the pond again and shouted, "Fish! Fish! " . To his surprise, nine fish swam over even before he could throw the fish food into the water. The next day, the number of catfish he summoned increased to 13. Eriksson described the experiment in a letter to his colleagues as a reference for fish's memory ability. [9]
Tony J. Pitcher, a ichthyologist at the University of British Columbia in Canada, once described an experiment in the book Fish Cognition and Behavior. In his laboratory, two test tubes of different colors are placed in the goldfish pond. Goldfish can only get food if they choose the right color. After training for a period of time, take out the color tube. A year later, when the researchers put the test tube into the pool again, the goldfish immediately chose the test tube that could get the color of the food [9].
Eriksson's observation and Pitcher's experiment show that fish are likely to have a memory of one to several years. Considering that most fish can only live for a few years, their memories are quite lasting. In addition, some studies show that the famous migratory fish salmon can return to their birthplace in adulthood because they have formed memories of the smell of their childhood environment. [ 10]
Why do fish have memories?
Why do fish have memories? This problem is very complicated, and many studies only reveal some possible reasons. If young zebrafish are given the aromatic smell of phenylethanol, these zebrafish will remember this smell until they reach adulthood. Studies have shown that after phenylethanol exposure, the expression of a gene named otx2 in olfactory epithelial cells of juvenile zebrafish increased significantly. Moreover, this gene remains at a high level even after zebrafish develops into adulthood. Interestingly, if young zebrafish are exposed to other odors, the expression level of otx2 gene will not increase continuously, which indicates that otx2 is probably the molecule that makes zebrafish remember the special odor of phenylethanol. [ 1 1]
Conclusion: The rumor is shattered. In other countries in the world, it is generally believed that fish only have a memory of 7 seconds (or 3 seconds). According to research by Ashley Ward of the University of Sydney, this sentence comes from an advertisement. But perhaps because of the long history, the exact source is hard to find. Ward also believes that early zoologists used overly complicated methods to test the memory ability of fish. These tasks suitable for human intelligence test are obviously too difficult for fish, so the experimental fish left a poor record, which may also be one of the reasons for this myth [12]. In a word, all the studies on the memory of fish show that the memory of fish is far more than 7 seconds. Although the phrase "fish's memory is only 7 seconds, it will never be boring" is beautiful, but it is only a legend.
References:
[1] Does Baidu know that the memory of fish is only seven seconds?
[2] Soso asked: Does the fish have a memory of only 7 seconds?
[3] Agranov BW, Davis RE, Brinkejj. Chemical study on memory fixation of goldfish. Brain resolution 1966; 1(3):303-9.
[4] CsányiV, CsizmadiaG, Miklosi A. Long-term memory and recognition of another species in paradise fish. Animal behavior. 1989 June; 37(6): 908-9 1 1.
[5] (1, 2) William Fei, White D, Messer WS. Simple spatial alternation task for evaluating zebrafish memory function. Behav process June 28th, 2002; 58(3): 125- 132.
[6] Sison M, Gerrai R. Associative learning of zebra fish (Danio rerio) in the plus maze. Behave Brain Research 20 10 February11; 207( 1):99- 104.
[7] Yu L, Twitch V, Kishi Nobusuke S and Zidanova IV. Cognitive aging in zebrafish. Public library of science no.1. 2006120 February; 1:e 14。
[8] Gaekwad S, Stuart A, Hart P, Wang K, Pieete V, Kashat J, and Carroue F. Af's acute stress interfered with zebrafish's performance in cue and spatial memory test: using fish model to study the interaction between stress and memory. Behav process 20 1 1 jun; 87(2):224-30.
[9] (1, 2) Long-term memory of Stefan Rib fish. 2008.
[10] Whitloc, K.E. Olfactory imprinting and environmentally induced gene expression: Is it possible to manage salmon populations through environmental control?
[1 1] harden MV, Newton LA, Lloyd RC, whitlock KE. Olfactory imprinting is related to the changes of gene expression in olfactory epithelial cells of zebrafish. Neurobiology. 2006 1 1 month; 66( 13): 1452-66.
[12] Memory Theory of Fish