Aksu-Koç's empirical research on Turkish children's acquisition of the past tense forms the basis for this original and important contribution to the current debate among psycholinguists on the interrelationship between language and cognitive development. Turkish, in its grammar, makes a clear distinction between direct and indirect experience, separating personal observation of processes from both inference and narrative. This distinction thus provides an ideal method of observing linguistic and neurolinguistic conceptual development. Aksu-Koç exploits this technique to its full advantage in a study conducted across a wide range of ages. The data are meticulously analyzed and the theoretical implications for a neo-Piagetian paradigm are carefully considered.