This is an imaginary screen (filter) that blocks the input if it is "up" and allows the input to get in if it is "down." The lower the anxiety level, the lower the filter. Keep the anxiety level low--remember, comfort is key in second language learning! Lower the filter by lowering the anxiety, raising the self-esteem, and motivating the student to learn. Too much anxiety can impede language acquisition. Stephen Krashen says keep it low by focusing on communication (meaning and content) rather than language form and grammatical accuracy.