1. A stressor detection system comprising: a sensor adapted to be attached to a person for obtaining a time-varying signal representing a first physical quantity relating to an environment of the person, and a processor which receives the time-varying signal from the sensor, compresses the time-varying signal to obtain a compressed signal, derives an amount of complexity included in the received signal by comparing the received signal and the compressed signal, and derives a first stressor value from the amount of complexity representing a degree to which the environment is inducing stress in the person, wherein signals with larger amounts of complexity derive a higher stressor value; an output which provides feedback related to the stressor value.