- Good examples of behaviors - 'I may be wrong but...' is a typical closed mind unless followed by a question. - Ray Dalio, 
- Only on esperm gets in - Closed-minded people have trouble holding two thoughts simultaneously in their minds.
This reminds me of the memorable quote by Charlie Munger: “The human mind is a lot like the human egg, and the human egg has a shut-off device. When one sperm gets in, it shuts down so the next one can’t get in.”
Open-minded people can take in the thoughts of others without losing their ability to think well—they can hold two or more conflicting concepts in their mind and go back and forth between them to assess their relative merits