Summarizing research activities from January 1977 to September 1978, this is the fourth annual report of research on speech processing conducted in the Department of Psychology at Indiana University. The report includes extended manuscripts, short reports, progress reports, and information on instrumentation developments and software support. The report contains the following eight articles: "Adaptation of the Relative Onset Time of Two-Component Tones" (D. B. Pisoni); "Identification and Discrimination of a New Linguistic Contrast: Some Effects of Laboratory Training on Speech Perception" (D. B. Pisoni and others); "Some Developmental Processes in Speech Perception" (R. N. Aslin and D. B. Pisoni); "Susceptibility of a Stop Consonant to Adaptation on a Speech-Nonspeech Continuum: Further Evidence against Feature Detectors in Speech Perception" (R. E. Remez); "Dual Processing vs. Response-Limitation Accounts of Categorical Perception: A Reply to Macmillan, Kaplan and Creelman" (A. J. Perey and D. B. Pisoni); "Perceptual Analysis of Speech Sounds by Prelinguistic Infants: A First Report" (R. N. Aslin and others); "KLTEXC: Executive Program to Implement the KLATT Software Speech Synthesizer" (D. Kewley-Port); and "Graphic Support for KLTEXC" (T. Carrell and D. Kewley-Port). Lists of publications and of laboratory staff and personnel conclude the report. (SR)