Radiation damage in lithium-containing solar cells Final report, 21 Jun. 1966 - 20 Mar. 1968

Interaction of lithium with defects induced in silicon solar cells by one MeV electron bombardmen

Food cleaning in gorillas: Social learning is a possibility but not a necessity

Food cleaning is widespread in the animal kingdom, and a recent report confirmed that (amongst other behaviours) wild western lowland gorillas also show food cleaning. The authors of this report conclude that this behaviour, based on its distribution patterns, constitutes a potential candidate for culture. While different conceptualisations of culture exist, some more and some less reliant on behavioural form copying, all of them assign a special role to social learning processes in explaining potentially cultural behaviours. Here we report the results of an experiment that tested to what extent food cleaning behaviour in a group of captive Western lowland gorillas (Gorilla gorilla gorilla) relies on social learning processes. Subjects were provided with clean and dirty apples. When they were provided with dirty apples, all subjects showed evidence of food cleaning in at least 75% of trials. Preferred cleaning techniques differed between individuals, four out of five of subjects expressed a behaviour analogous to that reported in wild conspecifics. Given this occurrence of food cleaning in a culturally unconnected population of gorillas, we conclude that social learning is unlikely to play a central role in the emergence of the food cleaning behavioural form in Western lowland gorillas; instead, placing a greater emphasis on individual learning of food cleaning’s behavioural form

Individual acquisition of "stick pounding"" behavior by naive chimpanzees

Many studies investigating culture in non-human animals tend to focus on the inferred need of social learning mechanisms that transmit the form of a behavior to explain the population differences observed in wild animal behavioral repertoires. This research focus often results in studies overlooking the possibility of individuals being able to develop behavioral forms without requiring social learning. The disregard of individual learning abilities is most clearly observed in the non-human great ape literature, where there is a persistent claim that chimpanzee behaviors, in particular, require various forms of social learning mechanisms. These special social learning abilities have been argued to explain the acquisition of the relatively large behavioral repertoires observed across chimpanzee populations. However, current evidence suggests that although low-fidelity social learning plays a role in harmonizing and stabilizing the frequency of behaviors within chimpanzee populations, some (if not all) of the forms that chimpanzee behaviors take may develop independently of social learning. If so, they would be latent solutions –behavioral forms that can (re-)emerge even in the absence of observational opportunities, via individual (re)innovations. Through a combination of individual and low-fidelity social learning, the population-wide patterns of behaviors observed in great ape species are then established and maintained. This is the Zone of Latent Solutions (ZLS) hypothesis. The current study experimentally tested the ZLS hypothesis for pestle pounding, a wild chimpanzee behavior. We tested the reinnovation of this behavior in semi-wild chimpanzees at Chimfunshi Wildlife Orphanage in Zambia, Africa, (N=90, tested in four social groups). Crucially, all subjects were naïve to stick pounding before testing. Three out of the four tested groups reinnovated stick pounding – clearly demonstrating that this behavioral form does not require social learning. These findings provide support for the ZLS hypothesis alongside further evidence for the individual learning abilities of chimpanzees