Encodes counting, whole numbers, and absolute quantities.
What It Does
Number.Cardinal neurons activate on counting integers and absolute quantity references. They fire on explicit numerals ('seven', '42', '1,000'), implied counts ('a dozen', 'a hundred'), and cardinality contexts ('how many', 'the number of'). They represent the most primitive form of quantitative processing — the idea that things can be counted and compared by count.
How It Behaves
Cardinal neurons are well-distributed across all layers, reflecting that quantity is a cross-cutting concern in language. They show particularly strong activation in middle layers where numerical entities are being integrated with their surrounding context — '7 billion people' requires both the Cardinal signal and Identity.Place or Identity.General to properly link the number to what it counts.
Research Example
In Llama 3.1 8B, Number.Cardinal neurons are active on 'there are 206 bones in the human body' regardless of whether the specific count is correct. The model has Cardinal neuron firing from the numerical context, independent of factual accuracy — which is why factual number hallucinations (wrong count, correct context) have a distinct neuron signature from confabulation hallucinations (wrong context entirely).