Watching others makes people overconfident 

To find out whether this perception is borne out by actual performance, Kardas and O’Brien tested a group of 193 participants on their dart-throwing abilities. Those who watched a demo video 20 times estimated that they would score more points than those who saw the video only once–this high-exposure group also predicted that they would be more likely to hit the bull’s-eye and reported that they had learned more technique and improved more after watching the video.

But these perceptions did not line up with reality: People who watched the video many times scored no better than those who saw it once.

Kardas and O’Brien found evidence for this phenomenon in other domains, including doing the moonwalk, playing a digital computer game, and juggling. The more that participants watched others perform these skills, the more they overestimated their own abilities.

Why does repeatedly watching a video breed such overconfidence? Participants who watched a variation of the tablecloth trick video that did not show the performer’s hands evidenced no exposure-related overconfidence, suggesting that people may feel confident only when they can track the specific steps and actions in performing a skill.

Source: Watching others makes people overconfident in their own abilities