After being a professional trainer for 30+ years, I've seen many examples to show how intelligent horses can be.  One of my current horses, Duchess, that I've owned for 8 years, has been exceptionally smart.  She and I have bonded so tightly that it seems like we can read each other's mind, and she is constantly trying to communicate her thoughts to me.  One example was a day she wanted out in the field adjoining her paddock.  I was standing in her stall door and she was up at the gate to the field about 80 feet away.  I just stood watching as she left the gate, walked all the way down to me, reached out her nose to touch my arm, then turned and loped back up to the gate, stopped, and looked back at me.  I pretended not to react to see what she would do next.  Amazingly, she again walked the 80 feet back to me, again touched my arm with her nose, loped back up to the gate, and looked at me.  Now, that is truly trying to say something.  Of course, I let her out into the field.  Horses are also great at getting our attention in other ways.  Back to Duchess, if I'm standing around talking to people and ignoring her, she will roll her tongue into a U shape, stick it out, and then flap her bottom lip loudly.  Naturally, all talking stops so we can make a big fuss over her funny antics.  She loves being the center of attention.  I've seen lots of other horses make faces, too, to draw attention, but usually they also do it when they're alone, bored, or sour in their stalls (as a vice), Duchess only does it when people are present and ignoring her.  She wasn't always such a people horse though, when I got her at 5 years old I was her 7th owner!  She had learned that riders would get off if she bowed up, crow hopped, and bolted a short distance.  The man I bought her from said he had owned her for a year and only been on her one time.  Of course, when I got her home, she pulled the same thing with me, but, I wouldn't get off.  I had some rides where I thought "I'm gonna die!", but eventually she decided it would be better to join me than fight me.  After a couple years she had become a pretty good show horse with over 436 PtHA national points, several National Top 5 titles, and a Reserve National Championship in HUS.  But even though she is great in the show ring I have to constantly be on guard for her trying to outsmart me.  If we're doing dressage manuveres like flying changes, shoulder in, haunches in, half pass, etc., she will volunteer them and as much as say "Just leave me alone, I can do this without your help, cuz I"m smart!".