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How do scientists measure a thought? While the great philosophical questions about the nature of meaning have been debated for centuries, the last few decades have seen the development of a sophisticated scientific toolkit designed to turn these abstract queries into concrete, measurable data. In this episode of Codex Mentis, we go behind the curtains of cognitive science to explore the very methods used to investigate how the human brain processes language and constructs meaning.

Moving from the 'what' to the 'how', this programme offers a detailed review of the modern psycholinguist's toolkit. The journey begins with the foundational behavioural paradigms that capture cognition in milliseconds. Discover the logic behind the Lexical Decision Task, where a simple button press reveals the speed of word recognition, and the Semantic Priming paradigm, which uses subtle manipulations of time to dissociate the mind's automatic reflexes from its controlled, strategic operations.

From there, the discussion delves into the neuro-cognitive instruments that allow us to eavesdrop on the brain at work. Learn how Electroencephalography (EEG) and its famous N400 component provide a precise electrical timestamp for the brain's "sense-making" effort. Explore how Functional Magnetic Resonance Imaging (fMRI) creates detailed maps of the brain's "semantic system," showing us where meaning is processed. And see how Eye-Tracking in the Visual World Paradigm provides a direct, observable trace of the brain making predictions in real time.

Finally, the episode demystifies the complex statistical techniques required to analyse this intricate data. We delve into the shift from older statistical methods to modern Linear Mixed-Effects Models, which are designed to handle the inherent variability between people and words. The conversation concludes with a crucial look at the foundations of trustworthy research, examining how scientists determine the sensitivity of their experiments and calculate the required sample sizes to ensure their findings are robust and reproducible. This episode provides a comprehensive guide to the ingenious procedures scientists employ to understand one of the most fundamental aspects of human experience: how we make sense of the world, one word at a time.

Sources and related content can be consulted at ⁠https://pablobernabeu.github.io/publication/pablo-bernabeu-2022-phd-thesis