1. A computer system for estimating quality of an interaction between a first participant and a second participant, the system comprising: a plurality of machine learning classifiers of extended facial expressions, each classifier of the plurality of classifiers being configured to generate a stream of estimates of the degree to which a predetermined emotion or affective state corresponding to said each classifier of the plurality of classifiers is present in a data stream of a first participant; a plurality of temporal filters, each filter of the plurality of temporal filters comprising an input connected to receive output of an associated classifier of the plurality of classifiers, and an output; and a machine learning function approximator configured to receive output signals from the plurality of temporal filters, the function approximator being trained to generate one or more estimates of quality of the interaction between the first and second participants based on the output signals of the plurality of temporal filters.