tl;dr we're all nuts
Two recent articles tickled my interest in bias.
In The Observer (How cognitive illusions blind us to reason, an extract from Thinking, Fast and Slow) Daniel Kahneman reminds us that cognitive illusions are stubborn, particularly when one is exercising hard-won, high-level skills. He illustrates this using stock traders, saying that their skill in evaluating the business prospects of a firm is serious work that requires extensive training. "Unfortunately, [this skill] is not sufficient for successful stock trading, where the key question is whether the information about the firm is already incorporated in the price of its stock."
In The Economist, All power tends to corrupt is subheaded "But power without status corrupts absolutely". It describes an experiment in which subjects were asked to select tasks for a colleague to perform. Some of the tasks were demeaning. Before they made their selection, they were given a job they might respect or look down on (the descriptions read a little like fun vs dull testing roles) and a sense of whether they or their colleague had more influence. Those put into the position of having influence but no respect chose significantly more demeaning tasks for their colleague.
Some testers tell me that they do a skilled and difficult job, but don't get much respect. I believe them – and I've found that the articles above have helped me understand my own behaviour a little more clearly.