4. Sensory metrology tasks

4.1 Locating a signal in background noise

Man's sensory system is continually flooded with information from both the external world and his own body. This information creates background noise. The first question to ask, therefore, is what is the smallest amount of stimulus a subject needs to be given in order for a sensory signal to emerge from the background noise.

This quantity is called the differentiation threshold, or perception threshold.

The signal is then declared to be explored at the liminal level. The adjective "liminal" refers to the Latin limen and to the concept of a threshold value...