The "Slow Blink" has been a well-documented behavior for a long time. D4 calls it "lovey-eyes."
From John Scalzi's "Starter Villain."
“How do I look?” I asked Hera (the cat). I was not dressed in my usual substitute teacher uniform of dress shirt, sweater vest and Dockers; I was instead in my best suit, which was also my only suit, the one I’d worn to both my wedding and to my father’s funeral, and at no time in between those two events. It was actually only most of a suit, because apparently in the move back to my dad’s house I’d lost the shoes. I was wearing the black Skechers I had worn to dad’s funeral. No one noticed them then, and I was hoping no one would notice them today. “Would you give me a truckload of money if you saw me dressed like this?”
Hera gave a small chirrup and a slow blink, indicating her approval.”
“I hung up and looked at my cats. “Well, that was a delightful conversation,” I said to them. Hera gave me a slow blink in sympathy. Persephone padded over and meowed to be picked up. I complied with the request.”
