## 4 Discussion and Conclusions  
In order to investigate temporal aspects of speech processing, we performed an intelligibility test of mosaicized English words, in which the OMBD was compressed, preserved, or stretched in time. These manipulations did not change the acoustic information, but changed the speed of the speech. Listeners with three different language backgrounds (native-English, Indonesian, and Chinese) were employed to determine the intelligibility of mosaicized English words; they typed what theyhad heard. The results showed that, overall, for each language group, the highest intelligibility was obtained when the OMBD of the stimuli was preserved/stretched into 20 or 40-ms MBDs (intelligibility score for the English group: 76-78%; for the Indonesian group: 50-53%; and for the Chinese group: 44-53%). Compressing the OMBD caused a decrease in word identification by about 20% both for the 20-ms and the 40-ms OMBD. When stretched by a factor of 4 or 8, mosaic speech was basically unintelligible. The most important finding was that if the MBD for presentation was not longer than 40 ms, the intelligibility of mosaic speech was at the highest level when preserved or stretched. A second goal of this study was to investigate whether the effects of compressing, preserving or stretching mosaic speech would be similar among listeners with different language backgrounds. As expected, mosaic speech intelligibility was significantly higher for the native-English group than for the two non-native English-speaking (Indonesian and Chinese) groups in each OMBD. Nevertheless, compressing or stretching the speech resulted in similar trends in intelligibility among the three language groups. The intelligibility was relatively high for the preserved OMBDs of 20 ms and 40 ms for all language groups, and also for the stimuli with the 20-ms OMBD stretched into the MBD of 40 ms, but for the native-English group only. In conclusion, even when the same acoustic information was given to the listeners, intelligibility decreased when the speed of the speech was changed compared to when it was preserved. However, the intelligibility did not change significantly even when the amount of information must have changed (the OMBD of 20 ms and 40 ms contained different amounts of information) for the English and the Indonesian group at the MBD of 40, 80, or 160 ms. This is the same tendency as found in our preliminary experiment [34]. Regardless of language background, linguistic information in English is thus conveyed relatively well when presented within temporal blocks of 20 and 40 ms, either at a preserved speed or a stretched speed. This agrees with [PERSON] et al. 's (2018) [14] argument about the resemblance between the block duration of mosaic speech and the frame duration of motion pictures. The segment duration of 40 ms is similar as that employed in movies, in which visual motion is induced by presenting successive static pictures at the same intervals of 24 frames per second (i.e., frames of 42 ms [42]). They suggested that the temporal resolution of about 40 ms is necessary to perceive motion in general. Furthermore, as mentioned in the Introduction, this temporal segment size seems to be compatible with neural oscillations of 20-33 ms, which are considered to be involved in preserving phonemic intelligibility [19; 21]. Given the potential correspondence between the present intelligibility data and neuroscientific findings, it is feasible that mosaic speech can be used as an alternative to sounds in current hearing tests. Most testing nowadays is performed with pure tones or natural speech audiometry. With mosaic speech as test stimulus, it will be possible to more systematically assess how temporal and spectral aspects of speech processing develop or change over age, along with possible changes in human cortical functioning and vitality. Before considering practical implications of mosaic speech, the following needs to be addressed first.