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Abstract
Cognitive archaeology investigates tool-use and tool-making procedures to make inference about human cognitive evolution. These inquiries often trace the progressive complexity of artefacts through the archaeological record and deduce the cognitive abilities that accompanied technological changes such as language. However, the cognitive mechanisms underlying stone tool manufacture have not been investigated using validated methods. Thus, it is unclear whether these behaviours rely on linguistic resources or draw upon other neural circuits.
The aims of this thesis were to identify the working memory and neural resources associated with tool-use and tool-making. Dual-task experiments were performed on undergraduate students and experienced knappers to investigate whether tool-use and tool-making recruited verbal and/or spatial working memory resources. Positron Emission Tomography was also used to identify the brain regions recruited during stone tool manufacture and whether, as cognitive archaeology assumes, the manufacture of more complex tool forms recruits more sophisticated brain circuitry.
It was found that tool-use recruited spatial working memory and that verbal working memory resources were not required unless the task demands contained a specific verbal component. It was also found that the performance of the individual movement elements in non-hierarchical order did not tax spatial working memory above that required to perform the hierarchical sequence. These results were replicated with expert stone tool knappers, indicating that tool-making does not require input from verbal resources. Rather, stone tool manufacture recruits spatial working memory. Further, performance of the elemental knapping movements in a non-hierarchical order required spatial working memory resources comparable to actual stone tool manufacture.
These findings were supported by Positron Emission Tomography scanning which identified that manufacture of more complex tool forms did not necessarily recruit more sophisticated neural resources. Further, the performance of the elemental knapping movements in non-hierarchical order was more neurologically demanding than tool-making.
It was thus concluded that traditional investigative techniques of cognitive archaeology do not provide reliable insight into the cognitive processes underlying tool-use and tool-making. These results also cast doubt on theories which argue that stone tool played a direct role in language evolution.