Encodes additive linking — and, also, furthermore, in addition.
What It Does
Relation.Conjunction neurons activate on additive logical relationships: explicit conjunction markers ('and', 'also', 'furthermore', 'in addition', 'moreover'), list constructions ('X, Y, and Z'), set membership relationships ('both X and Y'), and accumulative reasoning ('not only X but also Y'). They encode the relationship of addition and co-membership between concepts.
How It Behaves
Conjunction neurons are broadly distributed across all layers, reflecting the fundamental role of additive relationships in language. They are among the most pervasive Relation sub-types and show consistent proportions across all models. They interact with Relation.PartWhole neurons (parts are conjoined to make wholes) and Boolean.Affirmation neurons (conjunction involves affirming multiple things together).
Research Example
In Llama 3.1 8B, Relation.Conjunction neurons activate on list-like structures regardless of explicit conjunctions — 'apples, oranges, bananas' produces Conjunction neuron firing despite the absence of 'and', because the comma-separated list structure is itself a conjunction signal. This is how models recognize implicit enumeration without always requiring explicit connectives.