One study, for example, gave managers negative background information about a fictional employee before they were shown that same person performing well at a negotiation task. Managers with a fixed view of personal attributes (they tended to agree with statements like "As much as I hate to admit it, you can't teach an old dog new tricks. People can't change their deepest attributes") subsequently rated the employee less positively than managers with a belief that people can change.
Another study found that managers who think people's attributes are fixed gave their staff less coaching, presumably because they think such interventions will be ineffective.
However, on a more positive note, there's research showing that managers who think people can't change, can be persuaded to the contrary by a range of exercises, including showing them scientific evidence for people's ability to change and getting them to think about why it is important for staff to develop their abilities.
Heslin and VandeWalle concluded that this body of research has real-world implications. "To enhance workforce productivity, cues for managers to adopt a growth mindset [a belief that people can change] could be built into performance evaluation systems," they said. "These cues might include written, verbal and video-based reminders to managers...that all employee skills tend to be developed over time with practice and helpful feedback."
Heslin, P.A., VandeWalle, D. (2008). Managers' Implicit Assumptions About Personnel. Current Directions in Psychological Science, 17(3), 219-223. DOI: 10.1111/j.1467-8721.2008.00578.x