In essence, they vaguely measure communication skills (the title summarizes this as "intelligence"): "Our first measure of intelligence is a 10-word vocabulary

In essence, they vaguely measure communication skills (the title summarizes this as "intelligence"): "Our first measure of intelligence is a 10-word vocabulary test in which the respondent is asked to identify which of five phrases supplies the correct definition of a given word (...) Our second measure of intelligence is an assessment by the interviewer of how well the respondent understood the survey questions (...)" And they measure trust based on the anwer to: “Generally speaking, would you say that most people can be trusted or that you can’t be too careful in dealing with people?” I can't say I'm amazed with the results they get. People who can't communicate well probably misinterpret or misunderstand situations more often, and this affects their trust standards.