Blink Once For Yes

I made a new friend last weekend, a city girl whose only pet is a small dog, and I had the opportunity to show her the barn and let her meet the mustangs.  She admired each of them, and relished being able to spend time in the presence of horses.  While she was petting Capri, and we were talking about mustangs and horses in general, she asked a question that I wasn't sure I could answer.  You know how when you're talking to your cat, and you're looking deep into his eyes, and he gives a slow, sure blink in response?

 My friend was wondering if horses do that, and I said I wasn't sure, but maybe, but if they do it seems less deliberate than when a cat does it.  I think dogs do it sometimes, but a horse?  It seems like they blink if I'm petting them, but when I'm talking to them they tend to stare.  What do you think?  Blink once for yes...