Canned laughter is used to manipulate our emotions making us 'feel' relieved as though we are laughing at something funny. Sitcoms and the like use this to make their 'comedy' seem funny although without the laughter track would you be so amused? Slavoj Zizek makes a comparison between canned laugher and charity. He says that charity in a capitalist system is like canned laughter in that it falsely gives us a sense of relief.
