Scenario:
A person on their way to an appointment witnesses someone drop a bunch of papers but doesn't stop to help.
When explaining someone else's actions people tend to immediately attribute them to their personality rather than look at the possible situational factors
i.e. "They're self absorbed"
When explaining one's own actions people tend to blame or cite the situational factors rather than attribute it to their personality.
i.e. "I was running late otherwise I would have stopped."
Person = Someone else
Person = You
In a similar vein, studies have found that people are less willing to donate to help victims of man-made disasters (i.e. wars, poor infrastructure or lack of preparation) versus natural disasters.
As Designers, we need to keep these biases in mind and make sure they don't influence the research and thought process behind our work.