KEY FINDINGS · HR and line managers intrinsically believe that high-performing companies have more progressive HR practices and effective HR functions. Likewise, they assume less successful companies have less effective HR functions. · Experienced people (such as senior executives with long tenure) are more likely to hold personal beliefs about the impact of HR practices on performance (i.e., implicit performance theories) than are less experienced people (such as graduate students). · These beliefs are likely to result in research that overestimates the impact of HR on firm performance.