Balancing act: A neural trade-off between coherence and creativity in spontaneous speech

Effective communication involves a delicate balance between generating novel, engaging content and maintaining a coherent narrative. The neural mechanisms underlying this balance between coherence and creativity in discourse production remain unexplored. The aim of the current study was to investigate the relationship between coherence and creativity in spontaneous speech, with a specific focus on the interaction among three key neural networks: the Default Mode Network, Multiple-Demand Network, and the Semantic Control Network. To this end, we conducted a two-part analysis. At the behavioural level, we analysed speech samples produced in response to topic cues, computing measures of global coherence (indexing the degree of connectedness to the main topic) and Divergent Semantic Integration (DSI; reflecting the diversity of ideas incorporated in the narrative). Coherence and divergence in speech were negatively correlated, suggesting a trade-off between maintaining a coherent narrative structure and incorporating creative elements. At the neural level, higher global coherence was associated with greater activation in the Multiple-Demand Network, emphasising its role in organising and sustaining logical flow in discourse production. In contrast, functional connectivity analyses demonstrated that higher DSI was related to greater coupling between the Default Mode and Multiple-Demand Networks, suggesting that creative speech relies on a dynamic interplay between associative and executive processes. These results provide new insights into the cognitive and neural processes underpinning spontaneous speech production, highlighting the complex interplay between different brain networks in managing competing demands of being coherent and creative.