External Attention LSTM Models for Cognitive Load Classification from Speech

Cognitive Load (CL) refers to the amount of mental demand that a given task imposes on an individual’s cognitive system and it can affect his/her productivity in very high load situations. In this paper, we propose an automatic system capable of classifying the CL level of a speaker by analyzing his/her voice. We focus on the use of Long Short-Term Memory (LSTM) networks with different weighted pooling strategies, such as mean-pooling, max-pooling, last-pooling and a logistic regression attention model. In addition, as an alternative to the previous methods, we propose a novel attention mechanism, called external attention model, that uses external cues, such as log-energy and fundamental frequency, for weighting the contribution of each LSTM temporal frame, overcoming the need of a large amount of data for training the attentional model. Experiments show that the LSTM-based system with external attention model outperforms significantly the baseline system based on Support Vector Machines (SVM) and the LSTM-based systems with the conventional weighed pooling schemes and with the logistic regression attention model.