before some Uni guru dreamed up the Psycho crap many a pilot applied, got thru due skill & lead a long & successful career as a commercial pilot.
That is absolutely true Wally. And I have had RPT pilots in my care who have been great FOs and totally psycho Captains; I have seen Check & Training captains whose students qualified
despite their instructor; I have seen pilots with a pathological inability to play by the rules rise and rise in their career because they were the one who got the job done.
Right up until he flew into a hill.
I think you would agree that there are some personalities that are better suited to single-pilot work and some better suited to multi-crew. In a small operation you can ill-afford that wrong person who can take down the morale of the whole base, or the whole pilot body.
The psych testing I have used was very very accurate and very descriptive of a person's character. We got all the Captains to participate in a validation study and it was very useful then as a recruitment tool, allowing us to identify the more desirable character traits in an applicant and to red-flag a very few.
The psych tests were only one tool in the selection process and an applicant with zero technical aptitude or bad referees would still get zapped. It
did help avoid hiring a total charmer who turned out to be a psycho.