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Equation 2 · Part 1 · Probing, Sparse Autoencoders, Patching, and Steering: The Main Interpretability Methods, Compared

Symbol h_ell

hℓ(x)h_\ell(x)
hℓh_\ell

What this part means

the frozen activation the network produces at layer ℓ\ell for input x , and w.

Its job in the formula

heh_ell is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.

Where the article explains it

where hℓ(x)h_\ell(x) is the frozen activation the network produces at layer ℓ\ell for input x , and w, b are the probe’s own parameters, trained on labelled examples the network never saw during its own training.

The passage around this formula

where hℓ(x)h_\ell(x) is the frozen activation the network produces at layer ℓ\ell for input x , and w, b are the probe’s own parameters, trained on labelled examples the network never saw during its own training. Nothing in that objective touches the network’s weights or its downstream computation. A probe reports only whether some linear function of this one activation predicts the label well.

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A subscript is a label attached below a symbol. It often selects a time step, component, category, or member of a sequence.

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Sources cited in the article section

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