Fig. 1

Schematic representation of the relationship between developmental mode [altricial offspring left, precocial offspring right], social brain size, social cognition and social complexity. Whereas the influence of developmental mode on variation in the ‘social brain size’ and ensuing cognitive abilities and the deduced effects on social complexity are well established (conventional view, light grey pathway; (e.g. [4, 6, 9–12, 14, 15, 17]), we emphasize a different idea in this review, namely that social complexity may not be associated with developmental mode despite differences in brain size (dark grey pathway; see Table 1). Whether socio-cognitive skills are similar or reduced in precocial and altricial species, however, cannot be determined due to the lack of systematic studies addressing these questions (Displayed by ‘??’ as well as a dashed circle of social cognition in the right pathway)