Researchers Keep Rejecting Grandmother Cells after Running the Wrong Experiments: The Issue Is How Familiar Stimuli Are Identified

There is widespread agreement in neuroscience and psychology that the visual system identifies objects and faces based on a pattern of activation over many neurons, each neuron being involved in representing many different categories. The hypothesis that the visual system includes finely-tuned neurons for specific objects or faces for the sake of identification – so-called ‘grandmother cells’ – is widely rejected. Here we argue that the rejection of grandmother cells is premature. Grandmother cells constitute a hypothesis of how familiar visual categories are identified, but the primary evidence against this hypothesis comes from studies that have failed to observe neurons that selectively respond to unfamiliar stimuli. We review these findings and show why they are irrelevant. Neuroscientists need to better understand existing models of face and object identification that include grandmother cells, and then compare the selectivity of these units with single neurons responding to stimuli that can be identified.