American scientists have discovered that monkeys can count, or at least do addition, but they do not yet know if they are able to learn multiplication. A team of six researchers from Harvard Medical School and Yale University School of Medicine found this out by successfully training three “symbol-literate” rhesus monkeys to add and combine pairs of large numbers. In a future study they plan to find out if monkeys can learn to multiply.
The study published in March 2014 and titled Symbol addition by monkeys provides evidence for normalized quantity coding, was lead by Margaret S. Livingston from Harvard’s Department of Neurobiology and involved training three young male macaque rhesus monkeys to connect “26 distinct symbols” with between zero and 25 “drops of reward.” The scientists then tested the monkeys to see if and how they could add or combine “symbolically represented reward magnitudes.” They found that the primates were able to transfer this ability to “a novel symbol,” which indicated that they were able to perform calculations rather than simply memorizing values of symbol combinations.
The three monkeys had already been trained to be symbol-literate, a concept previously studied by Livingstone who headed a earlier study that showed how with symbols, monkeys showed “linear, human-like, accuracy” using these symbols to “represent scalar value.”
Monkey Study Shows They Can Add
To determine whether monkeys can count, the six scientists taught the three monkeys chosen for the research project to do addition using two very distinct sets of symbols, plus dots that were shown on a computer-driven touch screen located in the monkeys’ cage. All three had previously been extensively trained to associate the 26 symbols or as many as 25 dots, with “reward values.” These were presented in the form of drops of liquid that corresponded with the value (or sum) that was the answer. At this stage, it was not known whether the monkeys could learn to multiply, or even whether they could “perform above chance on a difficult addition task,” but rather how they could combine quantities.
The researchers observed that the monkeys usually chose the larger option, and that they were very accurate when it came to discriminating the symbols in pairs. According to Livingstone, what they did was “fairly accurately” combine two of the symbols instead of simply memorizing the addition of pairs of numbers. She interpreted this as the monkeys’ way of getting the most out of “whatever is out there.”
The researchers also noticed that the monkeys’ abilities were more accurate with the first symbol set – which they had a lot of experience with – than with the second, newer symbol set. The study results describe exactly how they did this and exactly how and when they rewarded the monkeys with the drops of liquid.
While scientists are well aware that primates are not, and will never be “mathematically capable” in the same way as humans, they have known for a while that they are able to “estimate” numbers in groups and able to identify which groups are bigger than others. In this particular study, it appears that the primates made a larger number of mistakes that involved numbers than those that were identified as being “close in value.”
Those who have analyzed this research project point out that neuroscientists – which is what Livingstone is – have already proven that the human brain can distinguish less easily between two numbers that are higher than one another than two that are lower than one another. A typical example is that you or I would easily see and describe two or four birds in a tree. But if there was a flock of birds, we would be unlikely to be able to say whether there were 24 or 22 birds. In other words we would not be easily able to identify a difference of just two birds.
While we know this to be true, we cannot explain this phenomenon. Some scientists argue that we perceive distances between small numbers as being greater than those between large numbers because our brains encode numbers logarithmically. Others say that it is because our brains encode numbers in a linear way and so the number becomes “less distinct as the value increases.”
According to reviews of the monkey study that seems to prove that monkeys can count, this possible bias to a linear scale might have made the addition challenge easier for the monkeys. In fact they suggest that their training in this area might have been the key to the assumption that monkeys can count. But Livingstone has the last word for now, stating that by teaching them to learn multiplication in future research studies will show whether their ability to be able to do addition really does provide the key to whether monkeys can do math or not.
By Penny Swift