Primatology.net

When trained Macaques were given a choice of three answers in a computer game; one of which was correct, one incorrect, and an additional option to pass – macaques where shown to choose the latter option to pass rather than risk being incorrect. The macaques were rewarded for a correct answer, but an incorrect answer initiated a pause in the game until the next question.

The “pass“ option was used in an identical fashion to that of human participants, and the macaques were observed to show self-doubting behaviour – a trait which was previously thought to be unique to us. When capuchins were faced with an identical challenge, they failed to take this third option, and seemed unaware when they are likely to make an error.

More information and Video at; BBC – Earth News

The American Journal of Primatology has published a paper by primatologist Kimran Miller and colleagues, who studied urine washing behavior among a population of capuchin monkeys. Prior to this study there have been some wild claims as to why so many monkeys pee on themselves. Some of them are:

• Peeing one oneself helps the monkey improve their grip when climbing.
• Urine washing is a type of cooling mechanism done when it gets too hot.
  

But this new study from Miller suggest that urine washing among monkeys is all about social communication. From Nature‘s news coverage,

“Alpha males, for example, doubled their urine washing rates when being solicited by females. The researchers think this might be how males encourage females to continue paying attention once they’ve started.

And in 87% of fights or aggressive incidents, the loser of the battle washed in urine. The team suspects that this is also an attention-seeking behavior — in this case seeking sympathy. But more research is needed to be sure.“

I’d link you up to the original source article if only Wiley InterScience wasn’t down at the moment.