Physical blind spots
Do you know how many physical blind spots you have? Stop for a moment to consider that.
Most folks know about the one in each eye where the retina merges into the optic nerve bundle.
Let's look at a few others.
There's the blind spot that's defined by the field of view, or rather, everything outside of it.
You are not seeing when you blink.
Your brain takes snapshots as your eyes move, often falsely interpreting the inbetween spots in the phenomenon known as the confabulation of saccades.
And there's the general blind spot formed by staring at the same unmoving image for a time. Your retinal cells stop responding to the same stimulus and cease showing the image. It's a visual form of "If you can smell yourself, others have been smelling you for days."
Mental blind spots
The Heisenberg Uncertainty Principle applies to critical thinking as well. There are biases that influence the way one examines data, often automatically filtering out useful information.
We can look back and laugh at the ancients who let their preconceived worldview drive their analyses of the reality around them, forcing the not-round peg into the round hole (e.g., Ptolemy's epicycles). But be wary: we have our own preconceived notions.
A character in one of Robert Heinlein's novels notes that "specialization is for insects." An article on failure in the Jan. 2010 (18.01) issue of Wired Magazine notes a problem with specialists because they have trouble looking outside their own field for answers to non-field problems affecting their work.
Yet I'm going to challenge that notion about specialization just a bit. Specializing itself is not the problem -- it's the creation of blind spots in the process. It's not that we don't see. We see -- and reject or ignore.
Sometimes we just don't think. Example: A downtown meeting is held on Tuesday night to determine what weekday evening would best suit the members of a new social organization as a meeting night. What night do you think the attendees are most likely to pick? Why?
Avoid Intellectual Bluebloodedness
If you don't think you are a specialist: Do you have friends with opposing political and religious views? One of the "specializing" things we tend to do is to develop relationships with folks that already think as we do. This results in unchallenged biases and reinforced beliefs, ending in an us-versus-them way of thinking that is intellectually dishonest.
Don't just think positive; understand the negative. Don't just visualize success; study failure.