Non-cortical magnitude coding of space and time by pigeons

Abstract

Considerable research in cognitive science, neuroscience, and developmental science has revealed that the temporal, spatial, and numerical features of a stimulus can interact with one another [1,2, as when larger stimuli are perceived as lasting longer than smaller stimuli. These findings have inspired the prominent hypothesis that time, space, and number are processed by a ‘common magnitude system’ which represents these dimensions via the same unit of magnitude [3,4. According to current theorizing, the parietal cortex mediates this system [4]. To test the species generality and neuroanatomical foundations of this hypothesis, we asked whether space–time interactions can be observed in birds. Unlike mammals, birds lack a cortex [5,6; rather, they possess a neuron-dense pallium that is organized in clusters, in contrast to the laminar structure of the mammalian cortex [7]. Despite these striking neuroanatomical disparities, we observed reliable space–time interactions in pigeons. Our findings suggest that common magnitude systems are more widespread among animals than previously believed and need not be cortically dependent in all species. Work with mammals has shown that the temporal, spatial, and numerical features of a stimulus often interact with one another. Current theories suggest that the parietal cortex mediates these effects. De Corte et al. challenge this notion with evidence that pigeons, which lack a laminar cortex, also show systematic space–time interactions