Using a methodological approach adapted from field-studies with non-human primates, we observed the vocal behaviour of prelinguistic infants in one of their natural habitat, a nursery environment. We identified a number of vocalizations reliably triggered by specific contexts in the infants and conducted an acoustic analysis of the different call types. Our results show that prelinguistic infants produce different categories of vocalizations. Categorical production has also been observed in other primate species, for example Vervet or Diana monkeys. Computer modelling could aid the analysis of such data by simulating the perceptual processes at work in the receiver when perceiving and categorizing a call. This would move the way we analyze calls beyond an objective description of their acoustic parameters and more towards a representation of the perceptual processes involved in categorical auditory perception.