I personally don't see anything I'd recognise as the "Clever Hans" effect in sick animals. What I see is a lot of observer bias and a lot of coincidental recovery. These things apply just as much to conventional medicine as woo. It's just that you try to notice when they're happening and discount them.
Since the observer bias effect is all on the owners, I don't see why different colours and shapes of pill shouldn't have some influence.
Rolfe.
I think all this is absolutely true. In fact I would say "Homeopathy *does not* work on animals."
But there is one way that I think you can see the "Clever Hans" effect. Some vets use this stuff that is supposed to make animals calm if they smell it. (I only wish there were such a thing!) I've mostly seen this used on horses. Not mine, as I don't allow vets who do such things to touch any of my animals, but many of my friends believe in this stuff and take their horses to such vets. They even bring back tiny bottles of this magical fluid to use at home. Horses are such herd animals that if the owner is acting nervous or scared they will often become nervous, so the actual effect is on the owner! The owner believes it will calm the horse down and it does - but only because the owner is calmer.
Otherwise, yeah, what Rolfe said!