In the past few weeks, in various conversations with friends and colleagues, I've heard some people mentioned that they don't seem to have a great deal of interest in anything, and that they are mostly going through their routine on auto-pilot. 

At the same time, I've also seen from others that they are really excited about some topics that they just can't stop talking about. 

I've myself felt both ways on different topics at different times. 

The measure of how interested we are in anything is the number of follow-up questions that come up to our mind about what we are encountering. If what we're seeing / hearing / reading raises a lot of questions in us, then it is a strong indicator that we are interested in the topic. And when we don't have any follow-up questions popping up, then we aren't interested in the topic. 

The reason we don't have any questions may be because we aren't understanding the topic in the first place. While that may be true, it is also true that we can't sustain interest in a topic that we cannot understand. 

So how do we get interested in anything even when we aren't?

Just deliberately focus on coming up with follow-up questions on what you're encountering. If it isn't happening naturally, then force it. As you hear more answers, at some point, you will start doing this automatically.

This point can be reached very quickly for some topics (celebrity gossip) and might take a long time when we don't have basic fundamentals established to understand answers to our follow-up questions (molecular biology). 

Interest and learning are intertwined. 

We learn faster when we are interested. We learn slower (if at all) when we aren't interested as the learning process happens through the questions we have.