Since you want me to answer both parts, and you seem to prefer complete and thorough answers to short snippets, I will endeavor to provide you with both.
To understand the basis of cognitive bias, you have to go into what happens when you learn something. Learning is, at one level, the process of correctly applying a previously seen pattern to a new object, when you were not able to apply that pattern before. Learning a new word doesn't mean you only use that word at one specific object or one specific happening in time, you have learned the word when you can successfully apply it to very similar objects/occurrences. For example, “dog” is not just the four-legged creature sitting on the small mattress in the living room, but applicable to a huge number of four-legged creatures. “Coin” is not the particular piece of copper and zinc in my hand, but applicable to any number of small metal pieces.
Learning to recognize a pattern is a great tool for any mental equipment shed, but like any other tool, it can be misapplied. In particular, humans will identify patterns where none truly exist. If you flip a coin five times, and then show the sequence to a person, more likely than not that person will see a pattern and identify a “correct” sixth member of the sequence, even though there is no correct prediction to the sixth flip. This is combined with the natural human tendency to remember our successes and discount our failures. There is a great feedback loop in effect here, in that being right engenders positive emotions and being wrong engenders negative emotions. These two effects combine into a tendency to identify patterns, and then remember instances that confirm these patterns and discount instances that disconfirm these patters. This tendency is called cognitive bias.
So, when the original poster talked about how every bad driver fit a certain profile, that was seen through the lens of cognitive bias. You happen to notice that two or three bad drivers in a row fit a certain pattern. The pattern gets fixed in your brain. You start to notice more other drivers who fit your pattern, and ignore the drivers who go against it.
That’s why the original post can best be explained as cognitive bias.
