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. Author manuscript; available in PMC: 2019 Dec 1.
Published in final edited form as: Neurobiol Aging. 2018 Aug 24;72:83–88. doi: 10.1016/j.neurobiolaging.2018.08.018

Figure 2.

Figure 2.

Mean (± SEM) number of trials required for chimpanzees in each Age group to reach learning criterion of 10 consecutive correct responses for each of the 4 levels, or concepts, in the study. More trials were required with increasing subject age (P = 0.018) and with increasing Level number (P < 0.0001)