A couple of years ago a group of management scholars from Yale and the University of Pittsburgh tried to discover if there was a link between a company’s success and the personality of its boss. (46)To work out what that personality was, they asked senior managers to score their bosses for such traits as an ability to communicate an exciting vision of the future or to stand as a good model for others to follow. When the data were analyzed, the researchers found no evidence of a connection between how well a firm was doing and what its boss was like. As far as they could tell, a company could not be judged by its chief executive any better than a book could be judged by its cover.
(47)A few years before this, however, a team of psychologists from Tufts University, led by Nalini Ambady, discovered that when people watched two-second-long film-clips of professors lecturing, they were pretty good at determining how able a teacher each professor actually was.
Now, Dr Ambady and her colleague, Nicholas Rule, have taken things a step further. (48)They have shown that even a still photograph can convey a lot of information about competence—and that it can do so in a way which suggests the assessments of all those senior managers were nonsense.
Dr Ambady and Mr. Rule showed 100 undergraduates the faces of the chief executives of the top 25 and the bottom 25 companies in the Fortune 1,000 list. Half the students were asked how good they thought the person they were looking at would be at leading a company and half were asked to rate five personality traits on the basis of the photograph. (49) These traits were competence, dominance, likability, facial maturity (in other words, did the individual have an adult-looking face or a baby-face) and trustworthiness.
And Dr Ambady and Mr. Rule were surprised by just how accurate the students’ observations were. The results of their study, which are about to be published in Psychological Science, show that both the students’ assessments of the leadership potential of the bosses and their ratings for the traits of competence, dominance and facial maturity were significantly related to a company’s profits.
(50)Sadly, the characteristics of likability and trustworthiness appear to have no link to company profits, suggesting that when it comes to business success, being warm and fuzzy does not matter much (though these traits are not harmful).

锯割时压力的大小，应随材料的性质而变化，锯软材料时压力可大些，锯硬材料时压力要小些，工件快锯断时压力要减小。（）