
















• 
Products of
Experts multiply probabilities together. This



is equivalent to
adding log probabilities.



– 
Mixture models add contributions in the
probability



domain.



– 
Product
models add contributions in the log



probability
domain. The contributions are energies.


• 
In a mixture
model, the only way a new component can



reduce the
density at a point is by stealing mixing



proportion.


• 
In a product
model, any expert can veto any point by



giving that
point a density of zero (i.e. an infinite energy)



– 
So
its important not to have overconfident experts in a


product
model.



– 
Luckily,
vague experts work well because their



product
can be sharp.

