What is the "Halo Effect"?
The "halo effect" is a tendency in performance appraisals to assess an employee as outstanding because of one very impressive trait or accomplishment on the assumption that her other accomplishments were equally impressive. For instance, you were so impressed with the speed at which Patricia works that you ignore her rudeness to customers or failure to call back customers with the information they request.
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Sometimes, managers commit the "halo effect" because they are thinking of a recent incident, forgetting all those past incidents in which the same employee wasn’t so superlative. Rather than consider the entire year’s performance, these managers let one positive incident influence the twelve-month evaluation of the worker.
Managers may also be guilty of the "halo effect" when they have a rapport with an employee. The manager likes the individual, who is very pleasant to the manager, so he or she gets a good evaluation despite a mediocre performance.
The absolute opposite of the "halo effect" is the "horn bias," also called the "pitchfork effect." In this instance, there’s nothing that the employee can do to convince a manager that the employee is a good worker. Maybe the employee began the year poorly and then turned the performance around. But the manager fails to recognize the change, letting the earlier past mistakes blind him to the significant improvement in the employee’s work.
A good employee who associates with mediocre or average employees may also never be rated above average due to those friendships. Despite differences in the level of their performances, the manager rates the employee the same as his or her buddies.