A recent piece in the Harvard Business Review considers the evidence regarding the effectiveness of positive and negative feedback in work environments.
The review suggests that when it comes to motivating action, rewards may be more effective than punishments. It was also concluded that the inverse appears to be true, I.. that people are more efficiently deterred from actions when punishments are applied.
The work of the research team further suggested that the human brain encodes positive information better than negative information. In fact, people often assume that negative information is unrelated to them, but view positive information as very much relevant, which generates an optimistic outlook.