The study investigated the ability of 10-month-old infants, from monolingual English speaking environments, to categorize comforting and approving infant-directed speech (IDS) utterances across languages. Infants participated in an infant-controlled habituation procedure, in which they heard up to 12 different exemplars, in 12 different languages, from one class of ID utterance, either comforting or approving. Following habituation, the test phase consisted of two novel exemplars from either the same (control condition) or a novel (experimental) category in two different languages. The results did not support the hypothesis that infants categorize approving and comforting utterances across languages. In the experimental group infants did not increase looking time to novel category test trials, indicating they did not categorize approving and comforting utterances across languages. The researcher discusses factors such as the large amount of variability across languages, which may have contributed to infants' failure to categorize comforting and approving IDS across languages. (Contains 5 tables and 1 figure. The following are appended: (1) Native Speaker Survey Questions for the online rating study; and (2) Infant-Directed Speech Rating Questions for the online rating study.) [Master's Thesis, The University of Texas at Dallas.]