Several studies have investigated the effect of a particular linguistic environment on infants' discrimination of voicing for stop consonants. Exposure to contrasts phonemic for a community has been said to heighten preverbal infants' sensitivity to these contrasts.

This paper argues that phonetic input cannot be specified and ‘experience’ cannot be defined in this context without knowing how infants perceptually structure speech input. Consequently, the discrimination paradigm provides no test for the effect of experience on infants' speech discrimination. The conditions to be met in order to conclude an effect of experience are outlined.

This paper explores differences in conversational style among mothers. Although previous research suggests that many aspects of mother speech to the child covary in a way which serves the underlying intention of the mother, it was unclear whether such clusters of conversational behaviour would prove useful in characterizing stylistic differences among mothers across time. An analysis of the functionally-coded speech of 11 mothers showed statistically significant variability among mothers, especially in those behaviours most closely associated with intention. Further, mothers showed stability in these behaviour patterns across two sessions. A typology of mother style, based on the intentions of mothers to direct or converse with their children, is suggested and illustrated by individual cases.

Infants from a variety of linguistic backgrounds have been reported to babble similarly. The present study considers this possibility in detail, offering a concrete characterization of how babbling of Spanish- and English-learning babies is similar. Babbling of a group of Spanish- and another of English-learning infants (12 months of age) was recorded and transcribed by two experimenters, one a primarily Spanish speaker and one a primarily English speaker. Results show that in spite of gross phonetic differences between the adult phonologies of Spanish and English, babies from both groups produce predominantly CV syllables with voiceless, unaspirated plosive consonants. Vowel production is also perceived as notably alike. In the light of such similarities, possible differences in babbling of the two groups may be hard for even sophisticated listeners to notice.

Adjustments in speech made by 2- and 3-year-old children when talking to their 14-month-old siblings are described and compared with those made by mothers addressing their babies. ‘Clarification’ adjustments were made by all the children, but there were marked individual differences in the frequency of questions and ‘affective-expressive’ features – differences related to the quality of the relationship between the siblings. The pattern of speech adjustments reflected the social contexts in which the children addressed their siblings; within these contexts (prohibitory and playful) children as young as 2 make appropriate use of communicative devices. The individual differences between the children indicate two sources of influence on the adjustments made – pragmatic and emotional.

Children two to three years of age can spontaneously correct false statements and affirm true ones in a modified sentence verification paradigm. Such performances imply that very young children display knowledge of the rules of correspondence between language and reality (truth conditions) which are central to propositional logic, at an age when logical development in cognition has not been previously acknowledged.

Evidence provided by contrastive word order for agent and patient semantic categories in young children's spontaneous speech is confounded. Agents (effectors of the action) tend to be animate; patients (entities acted upon) tend to be inanimate. In an experiment designed to circumvent this confounding and to test young children's linguistic sensitivity to the role an entity plays in the action, nine children (2; 4·0–2; 11·5) described actions involving animate and inanimate entities playing both agent and patient roles. Four linguistic measures were observed. On every measure agents were treated differently from patients. For the most part, these agent–patient differences persisted when animate and inanimate entities were examined separately. These results provide evidence for the child's intention to talk about the role an entity plays, independent of its animateness, and also suggest that the child uses role-defined linguistic categories like AGENT and PATIENT to communicate these relational intentions.

Thirty-six 2- to 3-year-old children were given linguistic and non-linguistic tasks in order to determine whether the words front and back introduce the concept of ‘front–back’ orientation or whether the concept precedes the words. Contrary to prediction, a complex disjunctive concept of ‘front–back’ orientation was found to precede any knowledge of the words front and back. Results of the linguistic task show that the word back is comprehended before front, and further that children at an intermediate state of lexical knowledge interpret front as if it means back.

Modal auxiliaries have an epistemic and deontic sense and range in strength, e.g. must propositions are stronger than may propositions. Children (ages 3; 0–6; 6) heard two contradictory modal propositions of varying strength. In the epistemic condition, the propositions concerned the location of a peanut. In the deontic condition, they were commands by two teachers about what room a puppet should go to. The child was to indicate which command should be followed. The general acquisitional rule was: the greater the difference in the strength of the two modal propositions the earlier the difference was appreciated. Since the acquisitional history was similar across conditions, the two senses probably arose from a single lexical entry.