Monkeys trained to solve math problems are providing researchers with new insights into understanding a human learning disability in which children have difficulty adding numbers.
Margaret Livingstone, a neurobiologist at the Harvard Medical School in Boston, and her colleagues have taught three rhesus macaques how to add two numbers and compare them in value to a third, standalone number.
The numbers 0 through 25 were initially represented by select letters and Arabic numerals. Monkeys that picked the higher value between the two choices received a larger number of droplets of water, apple juice, or orange soda as a reward, Science Now reports.
The monkeys were able to be trained with this task in four months. To prove that the monkeys hadn’t just memorized combinations of symbols, researchers later introduced Tetris-like blocks to represent numbers, but the monkeys were again able to add.
When Livingstone and her team looked at the results in greater detail – they determined that the monkeys weren’t correct 100 percent of the time. Test results showed that the macaques would underestimate the sum of two numbers compared to a single one when their values were close, according to Science.
While adding numbers together, the monkeys would focus on the larger of the two and then add only a fraction of the smaller number to it. Such thinking would lead the monkeys to sometimes pick numbers like 13 over the sum of eight and six.
Research like this on how monkeys estimate the value of numbers could shed light on dyscalculia, a human learning disability related to math. Children with dyscalculia have difficulty adding numbers and guessing how many objects are in groups.
The results of this study, published in the journal Proceedings of the National Academy of Sciences on Monday, suggest that estimating values is a crucial step in the mammalian brain's ability to add correctly, Science Now reports.
“Being able to estimate obviously has survival value; you want to be able to glance up and see how many lions are about to attack you,” said David Burr, a psychologist at the University of Florence in Italy, who was not involved in the research.“The remaining goal is developing a model to explain how that happens in the brain.”