Social learning and spread of alternative means of opening an artificial fruit in four groups of vervet monkeys

Two-action experiments, in which observer individuals watch models use one of two alternative methods to achieve the same goal, have become recognized as a powerful method for studying social learning. We applied this approach to vervet monkeys, Chlorocebus aethiops, using an artificial fruit ('vervetable') which could be opened by either lifting a door panel on its front, or alternatively by sliding the panel to the left or right. In each of two groups a model was trained to lift the door and in two others the model slid it to either the left or right. Members of each group could then watch their model before the group was given access to multiple baited vervetables. Over the course of 100 openings we found a significant tendency for the lift and slide approaches to spread preferentially in the groups in which they were seeded. The same was true for slide left versus slide right, indicating these monkeys can attend to and learn from a fine level of detail in what others do. This effect cannot be explained by mere local enhancement since monkeys grasped a knob centred in the door to perform all techniques. Instead, imitation or emulation is implicated. No significant diminution of the tendency to adopt the seeded technique occurred among individuals learning later rather earlier in the study. Our results show that vervet monkeys have the capacity to learn from others by either emulation or imitation and what they learn has the potential to spread across their group. (C) 2012 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.