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And how did he grow so much more in seven years than he did in his first few decades? In Encounter At Farpoint, Data seems like he was just activated and never tried to blend in socially before.
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I think the writers had no choice there. They had to make Data obviously robotic in Nature so he could then show some character growth. If they had shown him as someone with thirty years of experience then he would have been pretty much like the Data of the future from "All Good Things..." that was so close to being human that you could hardly tell the difference so they had to cheat and make him like he had been activated a couple of years before.
What's ironic is that his brother Lore had functioned for a much shorter amount of time and yet he sounded much more human than Data ever did, likely because he was evil and full of malice and we see much more of these around than people like Data.