Fourteen-month-olds selectively imitated a sub-efficient means (illuminating a lightbox by a head-touch) when this was modeled by linguistic ingroup members in video-demonstrations. A follow-up study with slightly older infants, however, could replicate this effect only in a video-demonstration context. Hence it still remains unclear whether infants' apparent tendency to be selective in learning opaque manners of novel skills from linguistic ingroup members is, indeed, a characteristic constraining property of cultural knowledge transmission that can be reliably manifested in live demonstration contexts that are more representative of naturalistic learning environments. To answer this question, we aimed to replicate the original study using live demonstration with a group of older infants (N = 48; 28 females). We found that eighteen-month-olds imitated the opaque manner of sub-efficient means action as a function of whether the demonstrator was a speaker of their own language. In a no-demonstration control group, infants relied on the self-discovered efficient means (handaction), just like infants observing the foreign speaker. These findings suggest that selectivity in learning sub-efficient opaque actions from linguistic ingroups has evolved to support transmission of culturespecific manner of action practices shared within social groups.Humans are unique in their capacity to acquire and faithfully transmit culturally shared action routines. Given their cognitively opaque and arbitrary characteristics, while acquiring such customary, normative and sub-efficient action routines, naïve learners mostly rely on demonstrations by knowledgeable others . As shown by previous research, ostensive communicative signals (e.g., establishing eye contact and being addressed by infant directed speech) have a special role in aiding infants' acquisition of cognitively opaque information , 2009Gergely, Egyed, & Király, 2007). Ostensive signals facilitate infants' learning about the functions of novel tools despite the opacity of their demonstrated manner of operation and the manifested function served by the novel artifacts (Futó, Téglás, Csibra, & Gergely, 2010). They also help infants to form novel means-actions representations (Hernik & Csibra, 2015), highlight the hidden dispositional properties of objects (