Don't know about intelligence in fish but I do know about Oscars as I use to raise them for the Aquarium trade a number of years ago.

They can become tame, enough enough so as to eat from your hand and I even had one that liked his sides rubbed. I would feed him by hand and then he would come back and lay at the surface on his side for me to gently rub his side.

He was about 13" in length at the time this finally developed. Maybe he had indigestion and needed his belly rubbed, don't know. Never figured out why he would do that.

I had him in a 200 gal tank next to my recliner and he spent all his time at my end of the tank when I was sitting there. Then I got up one morning when he was about 7 years old and he was dead. Old age was the only thing I could figure. That was a bad moment for me even though he was just a fish