Selective attention: usually focus attention on one or a few tasks rather than many. To focus our resources means we at least process less information from other competing tasks. Process information differently depending on how we actively focus on a stimulus. Dichotic listening task: task where person hears two or more different recorded messages over earphones and is asked to attend to one of them. People were able to give general descriptions of unattended message i. e. gender of speaker, speech or noise; but not specifics i. e. the whole message, language. Filter theory: limits on how much information a person can attend to at any given time. Filter to select which stimuli to process further; process its meaning. Predicts all unattended messages will be filtered out. Cocktail party effect counters this; people switch attention when their name is said in unattended message.