1. A method for correlating pupillary response to the significant cognitive response of a subject subjected to a relevant stimulus, comprising: measuring the pupillary response of a subject subjected to stimuli in an environment; deriving data samples d(n) of the pupil diameter from the pupillary response; segmenting the data samples d(n) into a sequence of time-shifted windows, each window including a response period and a baseline period; extracting a plurality of spatio-temporal pupil features from the data samples d(n) in said response and baseline periods in each said window; for each said window, presenting the extracted pupil features to a classifier trained to detect patterns of said extracted spatio-temporal pupil features for relevant stimuli and generate an output indicative of the occurrence or absence of a significant cognitive response in the subject to a relevant stimulus.