The cognitive and neural bases of creative thought: a cross-domain meta-analysis of transcranial direct current stimulation studies

Creative thought enables humans to flexibly generate, evaluate and select novel and adaptive ideas according to different contexts. Decades of creativity research indicates that it involves at least two aspects: retrieval of previously acquired knowledge and manipulation of that knowledge. However, the cognitive processes underpinning these two aspects of creative thought remain underspecified. The broader clinical-cognitive neuroscience literature suggests that retrieval and manipulation of knowledge is underpinned by general purpose cognitive mechanisms supporting semantic cognition, controlled episodic memory retrieval, and executive mechanisms. To identify commonalities from converging evidence that points towards a unifying theory for the neurocognitive bases of creative thought, we reviewed and meta-analysed 152 studies from creativity and the relevant parallel cognitive neuroscience literature using transcranial direct current stimulation (tDCS). The results revealed three things: 1) current tDCS studies are heavily biased towards the frontal cortex (459/591 effect sizes; 77.7%); 2) only anodal tDCS over the left lateral frontal cortex promotes creativity (p <.01); and 3) anodal tDCS stimulation over the same region also promotes improvement in many other cognitive processes. The latter includes more efficient processing of semantic knowledge (p <.05), more accurate episodic memory retrieval (p <.05), better and more efficient manipulation of buffered knowledge (all p <.001), and more efficient response selection amongst competing options (i.e., task-setting; p <.01). By merging these previously separate literatures, tDCS studies support the notion that creative thought arises from general purpose cognitive mechanisms including controlled retrieval and temporary storage of semantic and episodic information, as well as executive mechanisms.