You don't know, but what I do, I compare the same equity P/C (whether they were bought or sold, since each transaction always has both sides) ratio over time and look for extremes. Greater than 1 have often indicated extreme pessimism (and thus has been associated with local bottoms) and under about .44 often indicated extreme optimism (and thus associated with local tops). When I can I take out large occasional chunks of QQQ leaps that appears as single large blocs, since these are, IMTO, associated with big platers hedges.
Zeev