When the presence of others leads to enhanced performance, it is an example of?

It is an example of "social facilitation".

Social facilitation otherwise called audience effect is the propensity for individuals to perform distinctively when within the sight of others than when alone. Contrasted with their performance when alone, when within the sight of others, they have a tendency to perform better on well-practiced undertakings and more regrettable on perplexing or new ones.