Temporal order judgment reveals local-global auditory processes

Speech signals can be considered as acoustic sequences composed of local units (e.g. phonemes) which form global acoustic patterns (e.g. syllables). Extraction of speech information at both local and global scales is essential for comprehension. To decipher this process, we employed the temporal order judgement (TOJ) paradigm and investigated how the auditory system processes acoustic sequences. We selected four vowel segments of 30 ms and generated short acoustic sequences. We then examined listeners’ performance on TOJ of the vowel sequences using a same-different paradigm. The data showed that acoustic changes on a local scale caused by reversing vowel segments modify TOJ performance. Furthermore, the effect of local changes was attenuated when inter-onset interval between vowel segments increases, where segments can be recognised individually. A follow-up experiment showed that recognition of each segment was modulated by segment position and indicated that positions of acoustic segments contribute differently to TOJ. The results suggest that listeners perform TOJ by perceiving global patterns of acoustic sequences, which are further modulated by acoustic details on a local scale. Acoustic information on the local and global scales determines concurrently identification of short acoustic sequences.