Thinking a year and a half old deer is as smart or wise as a 3 or 4 year old deer would be the same as saying you are no smarter or wiser now at your age than the average 15 year old is today. Just common sense.
If 2.5+ buck are so much smarter than 1.5 buck, why do only 20% survive hunting season?
BTW, before ARs 18% of the 2.5+ buck wouldn't have been AR legal.