Depression, speech intelligibility, and articulatory coordination

This study investigates the impact of Major Depressive Disorder and its characteristic psychomotor slowing on speech intelligibility. The speech-in-noise intelligibility task involved 176 native English-speaking listeners and 9 speakers with speech from 2 speaker states: very severe depression and in remission. Speaker intelligibility was rated across three signal-to-noise-ratio levels (-2, 0, and +2 dB). The findings suggest that depressed speech is at least as intelligible as in-remission speech. Linear mixed-effects modeling showed no significant difference in overall intelligibility between the two speaker states. Additional acoustic analysis used vocal tract variables to quantify underlying articulatory coordination. Acoustic and articulatory analyses revealed that depressed speech exhibits "simpler" articulatory coordination, characterized by reduced coarticulation and less target undershoot, challenging the conventional view that depression necessarily leads to poorly articulated speech.