The research team led by Elisabetta Visalberghi of the Institute of Cognitive Sciences and Technologies in Rome, Italy, has found that the capuchins actually test their stone hammers before use.
If a monkey thinks that the stone is not suitable for the job because it is too light or too likely to crumble, it will move on to find another stone best suited for the job.
During the study, the researchers gave capuchins the choice between artificial stones of similar size but different weight, and stones that were more or less likely to break.
They found that monkeys appeared to know how fragile different types of stones were, and always chose the heavy stones.
They also found that, if two or three stones looked identical, the capuchins would pick a stone at random and test it by lifting, moving, or tapping it.
The monkeys chose the heaviest or least fragile stone.
This might be due to the fact that the monkeys spend lots of time on the ground trying out many different stones.
"When a capuchin touched a light tool it almost immediately discarded it and switched to another stone to check if it was heavy enough," New Scientist magazine quoted Visalberghi as saying.
"This shows it is not just apes and hominins that can select a tool using sophisticated methods.
"Humans learn by trial and error and it's very likely that non-human primates share this with us," she added. (ANI)