Introduction; Multiple Trajectories to Human Language Acquisition: Domain-Specific or Domain-General? Karmiloff-Smith, A.; Paper; Bilingual Language Acquisition: Where Does the Difference Lie? Sebastian-Galles, N.; Commentary; Bilingual Language Acquisition. Commentary on Sebastian-Galles: Lieven, E.; Paper; Grammatical Difficulties in Children with Specific Language Impairment: Is Learning Deficient? Hsu, J.; Bishop, D.V.M.; Commentary; Productivity, Proceduralization and Specific Language Impairment. Commentary on Hsu and Bishop: Dabrowska, E.; Paper; The Emergence of Two Functions for Spatial Devices in Nicaraguan Sign Language: Senghas, A.; Commentary; Widening the Lens on Language Learning: Language Creation in Deaf Children and Adults in Nicaragua. Commentary on Senghas: Goldin-Meadow, S.; Author and Subject Index.