Sensation: the process by which our sense organs respond to and translate stimuli into nerve impulses sent to the brain. Perception: organizing the stimulus input and giving it meaning. Stages of sensation and perception: stimuli activate sensory receptors, sensory receptors translate information into nerve impulses, specialized neurons analyze stimuli features, stimulus pieces are reconstructed and compared to stimuli in memory, perception is then consciously experienced. Psychophysics: sensitivity to stimuli: absolute limits of sensitivity. Dimmest light in which we can see objects. Softest sound we can hear: recognizing differences between stimuli. The lowest intensity at which at stimulus can be detected. However, the environment contains a background level of stimulation for each sense and this level (the adaption level) must be overcome if a stimuli is to be detected. Stimulus detection: the amount of energy required to overcome the adaption level is known as the differential threshold and it is subject to variation with changes in circumstances, locke"s experiment.