Our brains are designed to recognize patterns and respond. So, when there is missing information, we tend to fill in the blanks. But, our ability to fill in the blanks is based only on the history of what has happened, neither randomness nor radical change is taken into account. That is, except when we will in the blanks with what we want to be true, even if that is counter to the patterns of the past, and especially if we have revised our memory of history to fit into the pattern of what we believe to be a truth.
Filling in the blanks in this way sounds analytical, mathematical, and even scientific. But, it’s can also be thought of as telling yourself a story. A story about what someone thinks about you, why something happened to you, or when/if you are ever going to get somewhere.
I do this all the time: at least every day, on some days every hour, and in some hours every minute. Often it makes me seem smart, quick, intuitive…when I’m right. Often it makes me feel safe, assured, protected…until I’m wrong.
I challenged myself recently to try not to believe a story I told myself in a situation without data. It was hard. I had been able to ignore the first version of the story, and the second (which incidentally was radically different from the first). But when story after story came to replace the last, I couldn’t hold out anymore. I started to believe it was the truth and (because it wasn’t a particularly positive story) it hurt, just like it had really happened. And then, it did really happen and it hurt again.
I wish I’d learned some sort of lesson from this latest experience. But, I’m still processing it. On one hand, perhaps filling in the missing data created a self-fulfilling prophecy. On the other, perhaps by feeling the pain before it really happened, I prepared myself to hurt less. I don’t know and by analyzing it too much, I’m just starting to tell another story.
From my Soapbox 
You’re being somewhat vague here, but jumping to conclusions is a human condition that’s practically unavoidable because our brains are wired to be superior pattern matchers.
Recently, a coworker and I were having a conversation about this exact topic, and I believe the #1 example of this problem in action is the antivax movement. Vaccinations have done so many amazing things, and yet the people who shun it tend to be both educated and wealthy. What’s up with that? Well, maybe their superior pattern matching capabilities are extrapolating causation more often than less intelligent people.
The scariest thing I see is when people’s actions fly in the face of the data. Recently I saw an experiment that went negative, and still people wanted to push forward with it! They felt so strongly that it was the right thing even in the face of poor results. Crazy.
Anyway, it’s a trap we all fall into. And it seems like the smarter a person is, the more likely they are to fall into it. But then again I might just be extrapolating out a conclusion there with no data to back it up :p