The applause should not be the only moment a performer feels the audience is present.

An audience communicates all the way through, or fails to. Performers can feel a room leaning in or checking its phone, and a crowd that gives nothing until the end has left the person on stage working in the dark for an hour before offering a verdict. Attention during is worth more than approval afterwards.

When you are in the audience for anything, from a school concert to a talk at work, give your attention visibly. Look up, laugh where it is funny, stay still in the quiet parts. It costs you nothing and it changes what the person at the front is standing in.