John really wants to understand his Ph.D project in experimental solid state physics at a deep level. He thinks the quantum measurement problem is really interesting and so he is reading a lot of papers about that. The software he needs for his experiment is functional but he does not like some of the way it interfaces with other software and so he is rewriting it all. In one month he is giving a talk at a conference and so he is not going in the lab for the next month because he wants to give a really nice talk. Whenever his advisor gives him a paper to look at he not only reads it but some of the background references. He spends a lot of time talking to people in a theoretical biophysics group because he thinks what they are doing is pretty interesting....
He is going to struggle to finish his Ph.D in the normal time frame.
Joan is very focussed on her Ph.D project in computational chemistry. She spends most of her time writing and debugging code. She only goes to seminars that she thinks are directly related to her project. The only papers that she has read are those written by her advisor. She rarely talks to students outside her research group. She will finish her Ph.D in a timely manner but may struggle to get a postdoc because she does not have the big picture or an ability to communicate with others outside her narrow area.
So there is balance between the extremes of John and Joan. Too many distractions is bad. But occasionally a "distraction" can be very helpful. I am not sure how to find the balance.
Harden McConnell was a very successful physical chemist. In the last few years of his life he wrote a fascinating scientific autobiography on a web site. In The Young Scientist - My experiences he writes
My main blunder throughout my career was a kind of scientific introversion – not paying attention to the scientific work of others. As a stellar example, Clyde Hutchison was starting up research on paramagnetic resonance not many steps away from where I sat in the Eckhardt Physics building of the University of Chicago. It’s never too late to look over your shoulder and see what others are doing, and talk to them.I thank Steve Boxer for bringing Harden McConnell's site to my attention.