Taking the hint: Monkeys know when they know not

Human individuals hold the special capacity of thinking about their own knowledge. They can express what they know and what they don’t know. They will also seek for information only when they don’t know. A non-human individual, however, is largely thought to lack such metacognitive skills. Could it be that this seeming lack of metacognition is due to the fact that researchers have depended on highly verbal paradigms? Using two new non-verbal procedures—the “betting” paradigm and the “hint” paradigm—we asked whether monkeys could answer the following questions: First, can a monkey express what it knows and what it does not know? And second, if it knows not, will a monkey use that knowledge to gain more information? Our data will show that non-human primates share with humans knowledge that is critical for metacognition: an ability to monitor their memory traces and to control subsequent behavior in an effort to fill in missing memories.