# Influence of TTS Systems Performance on Reaction Times in People with Aphasia
###### Abstract  
Text-to-speech (TTS) systems provide fundamental reading support for people with aphasia and reading difficulties. However, artificial voices are more difficult to process than natural voices. The current study is an extended analysis of the results of a clinical experiment investigating which, among three artificial voices and a digitised human voice, is more suitable for people with aphasia and reading impairments. Such results show that the voice synthesised with Oginos TTS, a concatenative speech synthesis system, caused significantly slower reaction times than the other three voices used in the experiment. The present study explores whether and what voice quality metrics are linked to delayed reaction times. For this purpose, the voices were analysed using an automatic assessment of intelligibility, naturalness, and jitter and shimmer voice quality parameters. This analysis revealed that Oginos TTS, in general, performed worse than the other voices in all parameters. These observations could explain the significantly delayed reaction times in people with aphasia and reading impairments when listening to Oginos TTS and could open up consideration about which TTS to choose for compensative devices for these patients based on the voice analysis of these parameters. aphasia; intelligibility; jitter; naturalness; reading impairments; shimmer; text-to-speech systems +
Footnote †: journal: Medical  
artificial voice is best suited for PWA and acquired reading impairments. Since the quality of the artificial voices exponentially improved over the years, we also collected the reaction times during the clinical experiment. Reaction time is a parameter of cognitive load and may reflect difficulties and, thus, effort in processing information [7,8]. [PERSON] et al. [6] performed a similar experiment investigating the impact on the auditory comprehension of two different computer-generated voices ([PERSON] from the Windows platform and [PERSON] from the Macintosh platform) and one digitised human voice. The study compared the comprehension accuracy between the three conditions, showing that the digitised human voice's comprehension accuracy was significantly better than synthetic speech; however, the nature of the artificial voices was not clearly stated. Unlike [PERSON] et al. [6], the clinical experiment used in the current study collected the reaction times for each item and compared three different voices built with different technologies to investigate whether one voice is more suitable for PWA than the other voices. Another study investigating TTS systems in relation to PWA with acquired reading impairments is the one carried out by [PERSON] et al. [9], analysing participants' views of desired features, advantages, and downsides of TTS technology following one-on-one teaching and guided practice sessions. The results of the study highlighted that participants found (i) the possibility to select the preferred output voice, (ii) being able to tune the output speech rate, and (iii) text highlight matching the voice output to be crucial features of a TTS system. Other characteristics reported by some participants were the possibility to pause the TTS and to repeat. While these features could also be interesting for the healthy population, in the case of PWA and acquired reading impairments, being able to personalise the characteristics could be crucial for the use of the tool [9]. This experiment is part of a wider project aiming to identify which features improve or facilitate auditory comprehension in people who acquire aphasia and present acquired reading impairments. The current study has the following research questions: (i) Are the significant results in reaction times caused by one or more acoustic voice characteristics? (ii) If so, which one?