One travels more usefully when alone, because he reflects more.

Company fills the gaps where thinking would otherwise happen. Travelling with others, you trade observations, make joint decisions and see a place partly through their reactions, which is pleasant but crowds out your own impressions. Alone, the long quiet stretches push the mind to process what it is seeing, and you come back with more that is actually yours.

You do not need a long trip to test it. Take a walk, a train ride or an afternoon somewhere unfamiliar without anyone and without headphones, and notice what surfaces when nobody is there to talk to.