Humans may have the biggest brains, but having 100 billion nerve cells between the ears is no reason for people to believe they're the only creatures capable of seeing the world as both real and abstract.
So-called "lower" animals, monkeys in particular, are pretty good at supposedly "humans only" skills such as counting and calculating as well as doing memory tasks as well as most human beings.
The latest study by researchers of cognition and behavior at Utah State University and Duke University in North Carolina has found that Rhesus macaques are showing they possess another capacity thought to be unique to humans they count and sum combinations of what they hear and what they see.
In two experiments that essentially tested the hypothesis that animals in the wild use counting and sounds to assess situations and sum up threats to their territory, researchers found that animals can use sight and sounds in orienting themselves to situations. It's a capacity similar to a driver trying to determine if the number of cars in front at an
intersection will make him miss the green light.
The animal won't see the symbol "27" representing the individuals counted, but the processes are similar and likely necessary to survival for both mankind and monkeys, according to findings published in the current issue of the journal Cognition.
The same researchers as well as other teams in Great Britain and Germany who study cognitive abilities of monkeys have revealed that the primates' brains are hard-wired for counting and that chimps outperform humans at certain memory tasks.
Results from the newest study led by USU psychologist Kerry Jordan found that macaques can not only comprehend numbers as images and sounds, they recognize the abstract qualities represented by them. The research provides more evidence that math isn't a humans-only skill.
The research provides further evidence that animals have these precursors to math "very early on in the evolutionary line and early on in development," Jordan said.
Jordan and Duke colleague Elizabeth Brannon trained two 8-year-old female macaques to tap out the number of dots of varying sizes they saw on a computer screen. With each dot that appeared, the animals heard a corresponding beep. They were trained to tap a square on the screen for each dot that flashed on the screen: If they saw seven dots, they would tap the square seven times.
In the first experiment, two monkeys were trained to choose a simultaneous array of 1 to 9 squares that numerically matched a sample sequence of shapes or sounds. In the second experiment, monkeys presented with sample sequences of randomly ordered shapes or tones were able to choose an array of 2 to 9 squares that was the numerical sum of the shapes and sounds in the sample sequence.
The scientists state that in both experiments, accuracy and reaction time depended on the ratio between the correct numerical match and incorrect choice. These findings suggest monkeys, like humans, share an abstract numerical code that interprets a situation separate from the actual experience.
To determine if the monkeys were combining the two elements, Jordan and Brannon showed the animals a screen with two numerical choices one the correct amount of dots and one incorrect.
The monkeys were correct most of the time one chose the right answer 72 percent of the time; the other 66 percent. The greater the difference between the answers, the better the monkeys scored. They almost always could differentiate between one dot compared to eight dots. If the selections were different by just a single dot five versus six dots they seemed to have a much harder time making the correct choice.
More difficulty with the closely grouped dots could mean that the monkeys might be counting up to four or five dots but then just perceiving the grouping as "many."
Jordan points out that humans regularly make the same kind of errors when facing a snap numerical assessment, such as estimating the number of people in a crowd. Also, the monkey's ability to add numbers seen and heard together is an important survival skill for monkeys living in the wild.
"If you have an animal trying to make a decision to defend its territory, it's going to want know how many other animals it has to deal with," she said.Brannon said the new study supports the notion that nonhuman primates really can understand the meaning of numerals. "Although monkeys don't have language, they can understand a symbol and what it refers to."