INDSCAL analysis of perceptual judgments for 24 consonants via visual, tactile, and visual-tactile inputs

Twenty-four normal-hearing subjects received CV stimuli of uni- and bisensory inputs through the visual (speechreading), tactile (touch), and visual-tactile (speechreading and touch) modalities. Stimuli were presented via either a videotape monitor or a tactile vibrator or both. The purposes were to investigate the contribution of the tactile modality in uni- and bisensory conditions, and to analyze consonantal substitution errors to find perceptual features utilized by the subjects in their decision-making processes. The subjects' consonantal perceptions were phonetically transcribed and submitted to INDSCAL analysis which yielded mainly a four-dimensional solution. The interpretations of these dimensions were primarily closed bilabial, easy to see/hard to see, voiced/voiceless, and front/back place. Additional features were retrieved, but occurred less consistently.