ABSTRACT. – This paper briefly describes findings concerning the ontogenesis of behavioural and neural plasticity in cuttlefish. Predatory and defensive behaviours were investigated and learning and memory abilities were assessed during post-embryonic development. In parallel studies, the maturation of brain structures was determined at different ages. Learning abilities were poor and defensive strategies appeared relatively stereotyped in early juveniles. Memory developed and the plasticity of both defensive and predatory behaviour gradually increased during the first 3 months of life. These behavioural changes occurred simultaneously with the maturation of the most associative structures of the brain. Based on these laboratory observations, several hypotheses are proposed for the behaviour of juvenile cuttlefish in the field.