Ergativity is one of the main challenges both for linguistic and acquisition theories. This book is unique, taking a cross-linguistic approach to the acquisition of ergativity in a large variety of typologically distinct languages. The chapters cover languages from different families and from different geographic areas with different expressions of ergativity. Each chapter includes a description of ergativity in the language(s), the nature of the input, the social context of acquisition and developmental patterns. Comparisons of the acquisition process across closely related languages are made, change in progress of the ergative systems is discussed and, for one language, acquisition by bilingual and monolingual children is compared. The volume will be of particular interest to language... acquisition researchers, linguists, psycholinguists and cognitive scientists.;;The article examines four areas within ergativity that merit further consideration, including with respect to child language acquisition data: (1) syntactic alignment, including in particular the delimitation of semantic alignment from other kinds of alignment with lexical exceptions, and symmetric voice systems; (2) alignment splits, in particular the interpretation of exceptions to generalizations relating to animacy and definiteness; (3) syntactic alignment biases, especially the interpretation of exceptions; and (4) diachronic issues, in particular the decay of ergativity giving rise to idiosyncrasies like horizontal alignment or to conventionalized use of erstwhile ergative morphology.;;This chapter analyzes the development of ergativity in 20 bilingual and 11 monolingual children learning Basque by comparing their production of ergative case and agreement to their use of absolutive and dative case and verbal inflection. The children produced ergative verbal inflection earlier than ergative case; however, the opposite was true of dative indirect object agreement, which emerged later than dative case. Several potential factors which may influence the course of morphological development in Basque are evaluated, including morphological complexity, phonological difficulty and input frequency.;;One potential challenge for children learning Inuktitut comes from the ergative case marking system, because of the contrast between the ergative system in morphology and the accusative system governing syntax. However, no studies have yet been published focusing on how Inuktitut-speaking children acquire ergativity. In this chapter, we investigate this process using naturalistic spontaneous speech data from four Inuktitut-speaking children aged 2;0–3;6. We find that these children largely avoid producing structures that require ergative morphology. Analysis of caregiver speech and spoken narratives from older children and adults shows that this avoidance occurs regardless of age. We conclude that Inuktitut may be in the process of historical change from an ergative-absolutive system to a nominative-accusative system, and that the children’s language reflects that change.;;Ellipsis of core arguments in Warlpiri reduces the contexts in which children hear ergative case forms. The chapter discusses this and other possible factors that might impact on children’s acquisition of ergative morphology. Two sets of data are discussed. Naturalistic data show that by the age of three years children use ergative case in the appropriate contexts but have not mastered when to use the different allomorphs. At age four there are examples of ergative forms being used appropriately for agreement and instrumental case. The use of ergative morphology was not extended to non-ergative verbs and not restricted to past tense. The second set of data is based on adult and child narratives elicited with two picture books. It illustrates the contexts for using ergative morphology and the variability in whether subjects are included or omitted within and across age groups.;;In this chapter we present material on the acquisition of ergative marking on noun phrases in three languages of Papua New Guinea: Kaluli, Ku Waru, and Duna. The expression of ergativity in all the languages is broadly similar, but sensitive to language-specific features, and this pattern of similarity and difference is reflected in the available acquisition data. Children acquire adult-like ergative marking at about the same pace, reaching similar levels of mastery by 3;00 despite considerable differences in morphological complexity of ergative marking among the languages. What may be more important – as a factor in accounting for the relative uniformity of acquisition in this respect – are the similarities in patterns of interactional scaffolding that emerge from a comparison of the three cases.;;The acquisition of ergative marking in Chintang (Sino-Tibetan, Nepal) seems challenging: the marker covers several functions but is rare in discourse because of NP ellipsis and syntactic constraints. Based on a longitudinal corpus of four children, we ﬁnd that children master the ergative only after age 4. Earlier usage tends to be limited to restricted lexical environments, and for one child also slightly biased to the agent function (which is the most frequent function). In addition we ﬁnd a linear increase in spontaneous usage, accompanied by a decrease of usages where the child models her usage on an immediately preceding usage by an adult. This suggests that ergative acquisition chieﬂy relies on imitating and extracting input patterns and less on exploring generalizations.;;In the split-ergative pattern of case-marking in Hindi, the A-role argument typically receives ergative marking with verbs that have perfective inflection. Longitudinal data from three children acquiring Hindi (ranging in age between 1;5–3;2) and their caregivers reveal that ergative case-marking is produced infrequently. Since ellipsis of A-role arguments is rampant and children and adults rarely talk about completed events in the past, the conditions requiring the production of ergative case do not often occur. Nevertheless, children acquire the split-ergative case-marking system with little difficulty. In doing so, they may rely on multiple probabilistic cues to verb transitivity and grammatical aspect in the input: the perfective morpheme, the presence of overt O-role arguments, and the use of specific light verbs.;;This study examines the acquisition of split-ergative case marking in Kurmanji Kurdish, a language undergoing a shift in its case marking system, resulting in variable and inconsistent input to children. Data include naturalistic speech samples from a 12-month period from children (n = 12) from three age groups, 1;6, 2;6, and 3;6, and their caregivers (n = 41) and results from an Agent-Patient test. Descriptive and statistical analyses focus on adult patterns and children’s production at different ages. Results suggest that there are variable patterns in how adults use case. The children first use ergative case as early as 2;0 and show evidence of use of case and verbal agreement features productively repeated by 2;6. At these early ages, children use similar patterns to caregivers.;;This paper presents results of a comparative project documenting the development of verbal agreement inflections in children learning four different Mayan languages: K’iche’, Tzeltal, Tzotzil, and Yukatek. These languages have similar inflectional paradigms: they have a generally agglutinative morphology, with transitive verbs obligatorily marked with separate cross-referencing inflections for the two core arguments (‘ergative’ and ‘absolutive’). Verbs are also inflected for aspect and mood, and they carry a ‘status suffix’ which generally marks verb transitivity and mood. At a more detailed level, the four languages differ strikingly in the realization of cross-reference marking. For each language, we examined longitudinal language production data from two children at around 2;0, 2;6, 3;0, and 3;6 years of age. We relate differences in the acquisition patterns of verbal morphology in the languages to (1) the placement of affixes, (2) phonological and prosodic prominence, (3) language-specific constraints on the various forms of the affixes, and (4) consistent vs. split ergativity, and conclude that prosodic salience accounts provide the best explanation for the acquisition patterns in these four languages.;;Ergativity in Mayan languages is realized in the cross-referencing features on verbs rather than as case marking features on noun phrases. Overt absolutive markers appear with intransitive verbs. Some Mayan languages extend the ergative markers to intransitive verbs in aspectless complement clauses. The languages also make changes to transitive verbs in the same aspectless contexts. We evaluate how Mam, Q’anjob’al and Yucatec children acquire the extension of the ergative markers to intransitive verbs and the changes to transitive verbs in aspectless clauses. In each language we analyzed data of three children in the age range of 2;0 to 3;0. Our findings show that: (i) although the three languages have similar patterns of extended ergativity, children are sensitive to language-specific constraints on extended ergativity; (ii) the input frequency does not predict the acquisition of extended ergativity. We conclude that the structure of each language is responsible for the acquisition of extended ergativity.