The Hydra Effect: Emergent Self-repair in Language Model Computations
We investigate the internal structure of language model computations using
causal analysis and demonstrate two motifs: (1) a form of adaptive computation
where ablations of one attention layer of a language model cause another layer
to compensate (which we term the Hydra effect) and (2) a counterbalancing
function of late MLP layers that act to downregulate the maximum-likelihood
token. Our ablation studies demonstrate that language model layers are
typically relatively loosely coupled (ablations to one layer only affect a
small number of downstream layers). Surprisingly, these effects occur even in
language models trained without any form of dropout. We analyse these effects
in the context of factual recall and consider their implications for
circuit-level attribution in language models.
64c8648dcbcae9f106cd10d6
Thomas McGrath
64c8648dcbcae9f106cd10d7
Matthew Rahtz
64c8648dcbcae9f106cd10d8
Janos Kramar
64c8648dcbcae9f106cd10d9
Vladimir Mikulik
64c8648dcbcae9f106cd10da
Shane Legg
The Hydra Effect: Emergent Self-repair in Language Model Computations
We investigate the internal structure of language model computations using
causal analysis and demonstrate two motifs: (1) a form of adaptive computation
where ablations of one attention layer of a language model cause another layer
to compensate (which we term the Hydra effect) and (2) a counterbalancing
function of late MLP layers that act to downregulate the maximum-likelihood
token. Our ablation studies demonstrate that language model layers are
typically relatively loosely coupled (ablations to one layer only affect a
small number of downstream layers). Surprisingly, these effects occur even in
language models trained without any form of dropout. We analyse these effects
in the context of factual recall and consider their implications for
circuit-level attribution in language models.
Analysis reveals adaptive computation and downregulation mechanisms in language models, showing loose coupling among layers even without dropout.
causal analysis adaptive computation attention layer Hydra effect MLP layers maximum-likelihood token downregulation circuit-level attribution