[Context influence on the perception of dysphonia: when the knowledge of the patient's clinical state can modify the results of perceptual voice quality assessment].

Two experiments were conducted to examine how knowledge of the patient's clinical state affects the results of perceptual voice quality assessment performed by specialists in voice therapy. This study involved 53 patients with a dysphonia. For each speaker, we selected a pair of recordings made in different circumstances. These pairs of voices were presented to seven listeners (ENT surgeons or speech therapists). The task was to perceptually compare the severity of the dysphonia between the 2 recordings of the pair. Stimuli were presented first in a blind test, then several weeks later with accompanying information about the patient; in particular, whether the voice was pre- or post- treatment was explicitly specified. We balanced this artificial contextual information in order to (alpha) reinforce the blind judgment (for example, voices perceived as better in the blind test were indicated as post treatment); (beta) be inconsistent (in a clinical point of view) compared to the blind test (for example, voices perceived as more disordered during the blind test were indicated as post treatment). Results revealed that in the clinical-consistent context alpha, the preference was amplified in a significant way. In clinical-inconsistent condition beta, we observed an inhibition effect or a change of decision. In this condition, the judgment was more dependant on the contextual information (pre/post treatment) than on the auditory sensation obtained in blind condition. These findings are discussed with reference to results in the literature on visual, olfactory or auditory perception in context. In the frame of perceptual voice assessment, results revealed that only blind tests can provide reliable results.