The effects of text-to-speech system quality on emotional states and frontal alpha band power

The tolerance limit for acceptable multimedia quality is changing as more and more high quality services approach the market. Thus, negative emotional reactions towards low quality services may cause user disappointment and are likely to increase churn rate. The current study analyzes how different levels of synthetic speech quality, obtained from different text-to-speech (TTS) systems, affect the emotional response of a user. This is achieved using two methods: subjective, by means of user reports; and neurophysiological by means of electroencephalography (EEG) analysis. More specifically, we analyzed the frontal alpha band power and correlated this with the subjective ratings based on the Self-Assessment Manikin scale. We found an increase in neuronal activity in the left frontal area with decreasing quality and argue that this is due to user disappointment with low quality TTS systems as they become harder to understand.