1. A method of detecting and classifying mental states, comprising the steps of: detecting bio-signals from a bio-signal detector, the bio-signals including at least electroencephalograph (EEG) signals from a subject; using a processing device, transforming the electroencephalograph signals into a plurality of different representations, including separating the electroencephalograph signals into different epochs and generating representations of the electroencephalograph signal epochs in a plurality of different frequency domain representations, a plurality of different temporal domain representations and a plurality of different spatial domain representations; detecting values of a plurality of different properties of each of the plurality of different frequency domain representations, plurality of different temporal domain representations and plurality of different spatial domain representations; and applying a mental state detection algorithm to the detected values of the properties in order to classify whether the electroencephalograph signals indicate the presence of a predetermined mental state of the subject.