ARGUMENTA OECONOMICA No 2 (43) 2019 PL ISSN 1233-5835 ∗ Magdalena Brzozowska-Woś*, Bruno Schivinski** THE INFLUENCE OF INTERPERSONAL MOTIVATION ON POLISH CONSUMERS’ ONLINE BRAND-RELATED ACTIVITY The development of social media has a substantial impact on the surge of social engagement of Internet users. It is particularly prominent in the domain of content creation and content sharing. Such communication may contain various references to different products brands and companies. Internet users may refer to them explicitly or brands may be present in the background only. Therefore, it is pivotal for managers and researchers to isolate the factors that may trigger consumers’ brand-related engagement in the Internet. The objective of the research was to determine whether the susceptibility to interpersonal influence (both informational and normative) stimulates the three types of group behavior associated with consumer brand-related activity in the social media. The dedicated online survey was completed by 1,025 Polish consumers and analyzed using structural equation modeling (SEM). The results demonstrate that the factors of informational social influence – irrespective of its type – directly influence the consumers’ online engagement with brands controlled for age, gender, social media and brand usage. Regardless of whether the brand communication is initiated by some organization or by the consumers themselves, an eagerness to share the content perceived as valuable on social media plays a prominent role. Keywords: consumer’s online brand-related activities, COBRAs, susceptibility to interpersonal influence, Polish Internet users DOI: 10.15611/aoe.2019.2.09 1. INTRODUCTION In January 2016, active users of social media accounted for as many as 2.31 billion people around the world. In Poland alone, social networking sites were being used by 14 million people (Digital, 2016). Over the past decade, the Internet has evolved from a medium used exclusively for transferring information from an organization to consumers into a fully interactive medium in which – by means of social media – the consumers ∗∗ Gdańsk University of Technology. ** Birkbeck, University of London.