"That’s the way it's always been done" is an Internet meme that is interesting mostly because it is presented as a purely scientific psychological experiment, which has been widely shared in Runet, both on sites dedicated exclusively to memes and on humorous ones. This experiment has been credited to both Bernard Werber and Harry Frederick Harlow, although it has never been real, and, certainly, has no scientific description.

But before we start discussing science, let's get to the bottom of this experiment that never actually happened, shall we?
A researcher puts five monkeys in a cage. There’s a bunch of bananas hanging from a string, with a ladder leading to the bananas. When the first monkey goes for the bananas, the researcher sprays all five monkeys with freezing water for five minutes. Some time later, when a second monkey inevitably tries to go for the bananas, the researcher once again sprays all five monkeys with the cold water for five minutes. The researcher then puts the hose away and never touches it again. But, when a third monkey tries to go for the bananas, the other four attack him to prevent him from climbing that ladder. They are afraid of the punishment that may come.

Then, the researcher replaces one of the monkeys with a new monkey who wasn’t part of the original experiment and was never sprayed with water. And, as soon as he touches the ladder to go for the bananas, the other four monkeys attack him to keep him from doing so.  If he tries again, they attack him again. Thus, the new monkey learns not to go after the bananas because he’ll get attacked if he does.

The researcher replaces a second monkey with another new monkey. When this monkey goes for the bananas, the other four attack him, including the new monkey who was never sprayed with water. The researcher then continues to replace all the monkeys one at a time, until all five of the original monkeys are removed from the cage. Each time the newcomer goes for the bananas, the others attack, even when they, as new monkeys, have never received punishment for going after the bananas. And thus, the new monkeys, who have never been sprayed with cold water, learn not to go after the temptation of the bananas.

The researchers hypothesize that, if they were to ask the monkeys why they don’t go for the bananas, they’d answer “because that’s the way it’s always been done”.

We were very intrigued by this idea, for through a prism of humor and ridiculousness a very interesting thought was observed in this story. It touched upon Bandura's 1969 theories of social learning. We decided to experimentally establish validity of this experiment. But we adjusted it in accordance with the modern neuroscience discoveries.

The main goal of the experiment was to prove development of a desired behavior or reflex in the test animal in response to a certain stimulus, and to determine the probability of transferring this developed reflex to other specimens of the selected group, without direct influence on them from the outside (i.e. formation of a desired behavior in an specimen not directly, by stimulating it, but through learning by other mammals; creation of a "chain reaction"). Also, based on the social structure of the behavior of the tested animals, monkeys were replaced by rats (Rattus wistar), because their hierarchical structure of interaction in the group resembles the social life of humans.

Question one: determining the degree of stressfulness of conditioned stimuli or what are rats afraid of?

To determine the degree of stressfulness of our stimulus for rats, we developed a field model that consists of five zones. The area of the field itself was divided into zones, to which the tested rat was directed depending on the degree of stressor exposure. Thus, under influence of the maximum strength stressor, the rat gets into the far corner (zone number 5), and zone number 1 is the feeding zone, i.e. the more scared the rat is, the farther the corner it runs away. The number of each zone corresponds to the stress level.

In order to identify the most effective stressor for the rats, we tried 7 cycles of stimulation, according to the results of which we gave a certain score for each cycle, depending on the zone in which the tested animal was located. The stressors experienced by the rats were the following: exposure to light, sound, vibration and water. For the sake of clarity, in order to estimate the stress, we made a table that shows stressor variants, serial number of stimulation cycle, the number of stress points for each cycle and the total sum of points for all cycles.

According to the results of the experiment it turned out that under the influence of light on the tested rats, during all cycles of exposure, there was no change in their behavior (total score - 7), while under the influence of sound on them the total score was 23. At the beginning of the experiment the reaction to stress was at its maximum, but then (in the last two cycles) the rats did not react at all - they got used to it. At the same time, the reaction to stress was the strongest during influence of water on the animals (total score - 23), but there was no addictive reaction. From the third cycle, when the rats were influenced by vibration, there was practically no effect (total score - 11). On the basis of these results (Table 1) we came to the conclusion that the rats were most afraid of water.

Question two: determining the preferred manner of the unconditional stimulus or what do rats want?

In order to determine the ultimate unconditional stimulus (an innate desire that is difficult to control, similar to a banana and monkey situation), we made another table (to rate the stimulus according to (A) the reaction time to it and (B) the competition for food with neighboring species). In the experiment we used the following products: feedmill, bread, cheese, candy, and cooked sausage. Points for time were given relatively, which means that the maximum score (5 points), which is the fastest response result among all the unconditional stimuli studied, was obtained for stimulating the rats with cheese (the reaction time to cheese was 9 seconds). Further ranking was done in descending order: 4 points for stimulation with cooked sausage (reaction time - 11 seconds), 3 points for bread (reaction time - 12 seconds), 2 points for feedmill (reaction time - 15 seconds) and 0 points for candy (reaction time was detected, but did not stimulate the rats' interest). The second analyzed indicator was the attempt to take away food (stimulus) from other rats (competition). A score of 1 point was assigned for each attempt to take away a stimulus. Thus, the animals competed the most for feedmill and cooked sausage (there were 2 attempts to take away the stimulus and 2 points, correspondingly). Bread, candy, and cheese didn't cause conflicts (0 points each).

Question three: are mammals able to successfully navigate in space and learn the skill of overcoming it or which rats are "smart"?

In order to determine the intellectual activity of rats and further artificial selection of individuals with the best performance in orienting and navigating in space (revealing their ability to learn), a vertical maze was constructed. We chose the vertical maze version in order to motivate the rats to overcome obstacles and optimize the time spent on its traversal. Tested rats entered the maze one by one. At this stage we immediately eliminated the individuals unable to find the exit (considering their intellectual abilities to be low). Individuals who successfully coped with the task reentered the maze. Only those rats that completed the maze both the first and the second time were allowed to participate in the experiment, as cognitive abilities reflect the ability to learn (thus, we cleaned our sample).

Therefore, 250 rats of the same species (50 groups) were artificially selected favoring species with good learning abilities. Some of the selected tested animals were infected with staphylococcus aureus (as a provocation of biological mechanisms that determine behavior at the brain level). Later on, they developed an inflammatory reaction, which was confirmed by general blood tests (increased ESR).

Question four: Is it possible to transfer a learned behavior pattern or can we change the rats' habits?

The field experiment consists of a platform with a hole for liquid, an optimal stressor (water), a pole and a platform on which we put a stimulus (cooked sausage) is placed, and a container for liquid. Five rats, each taken from different families (to avoid conflicts), entered the described construction. Their daily food ration was reduced. When the starving rats began to climb up the platform with a stimulus (sausage), they were exposed to a stress factor (cold water).

With this experiment repeated several times the rats infected with staphylococcus aureus formed and established the connection: stimulus (food) - attempt to get it (action) - exposure to the stress factor (as a result). They learned to ignore the stimulus (food) and made no more attempts to get it, but that part of the tested animals whose bodies did not show inflammatory reactions (healthy species) did not show such a learning ability.

After that, we removed one of the five rats from the experiment, replacing it with an animal from a different group. The new rat did not yet know the "rules" and tried to climb up the platform to get the sausage, but those rats that had already been "taught" by the stressor what happens if you try to get the food attacked the newbie, not allowing it to get the stimulus. Thus, the new rat, having met resistance from the other test subjects, learned that it is not worth a sausage to take it (it developed a reflex). The experiment with replacement of rats was repeated until only those rats remained in the experiment, which were not affected by the water stress factor at all. At the same time the species, which were attacked by other rats "learned" by the stress factor, began to attack the others, preventing them from reaching the stimulus and experiencing the impact of the water stress factor. In the end, it turned out that none of the rats participating in the experiment were willing to make the effort to reach the stimulus, while "not really knowing" the reason for their learned atypical behavior.

We can come to the conclusion that pessimistically socialized mammals (naturally or artificially) are more submissive and less willing to express their will to achieve their own stimulus.