The Absolute Threshold
When we define the lowest intensity of a stimulus our brains can register on a sensory channel, we speak of its threshold. It sounds like a great name for a rock band, but the absolute threshold refers to the minimum amount of stimulation a person can detect on a given sensory channel. The sound a dog whistle emits is at too high a frequency for human ears to pick up, so this stimulus is beyond our auditory absolute threshold. The absolute threshold is an important consideration when we design marketing stimuli. A highway billboard might have the most entertaining copy ever written but this genius is wasted if the print is too small for passing motorists to see it.