Points in favour of cortical neuron counts as a proxy for moral weight:
Neuron counts correlate with our intuitions of moral weights. Cortical counts would say that ~300 chicken life years are morally equivalent to one human life year, which sounds about right.
That neuron counts seem to correlate with intuitions of moral weight is true, but potentially misleading. We discuss these results, drawing on our own data here.
I would quite strongly recommend that more survey research be done (including more analysis, as well as additional surveys: we have some more unpublished data of our own on this), if before taking the correlations as a reason to prefer using neuron count as a proxy (in contrast to a holistic assessment of different capacities).
That neuron counts seem to correlate with intuitions of moral weight is true, but potentially misleading. We discuss these results, drawing on our own data here.
I would quite strongly recommend that more survey research be done (including more analysis, as well as additional surveys: we have some more unpublished data of our own on this), if before taking the correlations as a reason to prefer using neuron count as a proxy (in contrast to a holistic assessment of different capacities).