Podcast with Stefano Ferraina on transitive inference and prefrontal cortex

Can monkeys reason logically , and if so, what does that look like at the level of single neurons? Neurophysiologist Stefano Ferraina presents evidence that prefrontal cortex neurons encode both symbolic distance and serial position during transitive inference, suggesting a neural substrate for logical reasoning in non-human primates. Subscribe for more from the Convergent Science Network podcast series. Stefano Ferraina joins Paul Verschure and Tony Prescott at the BCBT summer school to discuss his research on transitive inference in macaque monkeys. The task requires animals to learn an ordered sequence of abstract visual symbols through pairwise comparisons, then infer the correct ranking of novel, never-before-matched pairs. Surprisingly, monkeys master this within weeks and show a robust symbolic distance effect: comparing symbols far apart in the sequence is easier and faster than comparing adjacent ones, mirroring findings in human numerical cognition. The discussion carefully examines whether this performance reflects genuine logical reasoning or simpler reward-association mechanisms. Ferraina describes a critical control experiment using two separate chains that are subsequently linked, demonstrating that monkeys maintain the transitive ordering even when reward history alone cannot explain their choices. Recording from prefrontal cortex, he finds that roughly half of task-related neurons encode the symbolic distance effect, about 40 percent encode serial position, and a subset of around 20 percent encodes both , suggesting that the same neural population supports multiple aspects of the relational structure. Key topics include how transitive inference is defined and tested in non-human primates, why the symbolic distance effect challenges pure reward-association explanations, what the serial position effect reveals about how symbols are organized along a mental continuum, how the two-chain linking experiment strengthens the case for reasoning over association, the limitations of single-neuron electrophysiology for establishing causality, and what the overlap between symbolic distance and serial position coding in prefrontal neurons implies about the neural architecture of logical inference. Part of the Convergent Science Network podcast series from the BCBT Summer School.