# Infant Intersubjectivity Research, Theory, and Clinical Applications **Keywords:** Infant intersubjectivity, parent-infant communication, developmental disorders, pathologies of empathy, therapies. Abbreviations : ADS : adult-directed speech , DTV : double video link , F0 : fundamental frequency , IDS : infant-directed speech , IMF : intrinsic motive formation , IMP : intrinsic motive pulse , PDD : Pervasive Disintegrative Disorder , PRC : period of rapid change. **Opening (not a real abstract):** J. Child Psychol. Psychiat. Vol. 42, No. 1, pp. 3–48, 2001 ' 2001 Association for Child Psychology and Psychiatry Printed in Great Britain. All rights reserved 0021–9630\01 $15n00j0n00