Your question is based upon an assumption that 'inventing new things' is inherently better than 'studying and explaining existing phenomena'. It might feel so t

Your question is based upon an assumption that 'inventing new things' is inherently better than 'studying and explaining existing phenomena'. It might feel so to you, but it is not an absolute truth. Some people (like me) like to explore the vast wonders of nature rather than create an imperfect object that tries to mimic the perfection of nature (most inventions fall under this category). It's not a question of right or wrong or superiority or inferiority. To each, his/her own. And it's not about 'creativity' as another commenter explains either. Science, the art(!) of coming up with generalisations and laws expalining a vast array of phenomena calls for a lot of creativity. The top notch people in every field are there because they are creative. Creative in coming up with new mind-boggling explanations (can you get any more creative than coming up with Quantum mechanics? :) ), thinking of new ways to measure things, thinking of ways to put a new theory under 'stress test'. I don't understand what you mean by "Many computer scientists devote their time to studying other people's inventions (e.g., social networking, blogging, tagging, etc.)" but true scientists, the 'smart and ambitious people', are curious to understand everything. So, if they happen to be computer scientists interesting in social networking, etc., they might find it interesting to analyze and understand the dynamics of it; they like to tear things apart and look at the basics. If you ask for the 'social' utility of it, I could say such analyses form the basis of "inventing new things", but that's actually not the point; the scientists do it for their own curiosity. Just like you would feel rewarding to create an AI, they feel it rewarding to analyze it and understanding completely. >Why is that rewarding? This question, IMHO, is inappropriate - things are rewarding because they are. Each one is born differently, grows up differently and has different mindsets. There's no absolute measure on what 'must be' rewarding and what 'must not be'.