Organisms in their life-worlds recognize not only sensory inputs, but also functional tones, the use they need to make of certain stimuli if they are to do what they need to survive. ↑ Donald Norman, The Design of Everyday Things, ISBN 0-465-06710-7. Originally published under the title The Psychology of Everyday Things, often abbreviated to POET. ↑ Donald A. Norman (1999). Affordance, Conventions and Design.