The focus of this research is to determine how soon and to what extent infant abilities are influenced by listening experience. Fourteen English-learning infants and fourteen Spanish-learning 6-8 month old infants participated in a first experiment; eight additional English and Spanish-learning infants participated in a second experiment. Infants in Experiment I received a training stimulus pair followed by three randomly assigned natural language contrasts from English, Spanish, and Czech. Infants in Experiment II received three vowel contrast and two nasal contrasts. In this second experiment, infants had to attend selectively to differences in the acoustic signal which pertained to phonemic distinctions and ignored irrelevant features of the signal. Results of Experiment I indicated that Spanish-learning infants significantly discriminated the Spanish, English, and Czech stimuli; the English-learning infants showed discrimination of the English and Czech stimuli, but not the Spanish. Results of Experiment II indicated that all vowel contrasts were highly discriminable by both infant groups, and significant differences were observed in difficulty among the vowel contrasts. The discussion of the research to date centers on tentative suggestions about the role of experience and additional factors in speech-sound discriminability. (AMH)