One of a regular series on the status and progress of studies on the nature of speech, instrumentation for its investigation, and practical applications, this report covers the period of January 1-June 30, 1984. The 14 studies summarized in the report deal with the following topics: (1) sources of variability in early speech development, (2) invariance in phonetic perception, (3) phonetic category boundaries, (4) the categorization of aphasic speech errors, (5) universal and language particular aspects of vowel-to-vowel coarticulation, (6) functionally specific articulatory cooperation following jaw perturbation during speech, (7) formant integration and the perception of nasal vowel height, (8) the relative power of cues, (9) laryngeal management at utterance-internal word boundary in American English, (10) closure duration and release burst amplitude cues to stop consonant manner and place of articulation, (11) the effects of temporal stimulus properties on perception of the distinction between "sl" and "spl," (12) the physics of controlled collisions, (13) the perception of intonation from sinusoidal sentences, and (14) the nature of invariance. (FL)