Creating something out of nothing: Symbolic and non-symbolic representations of numerical zero in the human brain

Representing the quantity zero as a symbolic concept is considered a unique achievement of abstract human thought. Despite considerable progress in understanding the neural code supporting natural numbers, how numerical zero is encoded in the human brain remains unknown. We find that both non-symbolic empty sets (the absence of dots on a screen) and symbolic zero ('0') occupy ordinal positions along graded neural number lines within posterior association cortex. Neural representations of zero are partly independent of numerical format, exhibiting distance effects with countable numerosities in the opposing (symbolic or non-symbolic) format. Our results show that format-invariant neural magnitude codes extend to judgements of numerical zero and help motivate theoretical accounts in which representations of symbolic zero are grounded in more basic representations of sensory absences. ### Competing Interest Statement The authors have declared no competing interest.