Studies on the emergence of effects of socioeconomic inequality typically report that socioeconomic background is positively associated with early cognitive abilities. However, studies on looking behaviour in habituation tasks rarely investigate this association, although such tasks are standard in measuring cognitive abilities in infants. The current study aimed to explore the emergence and magnitude of the effects of socioeconomic background, as one aspect of socioeconomic inequality, on cognitive abilities in the first two years of life, using a dataset from a large-scale German cohort study. We modelled looking behaviour using growth curve modelling and found no significant effects at 7 months. However, we found positive effects of socioeconomic background on the initial looking time (intercept) and overall looking time at 17 months, but not on the looking decrement (slope). The results are discussed regarding the specificities of the data, as the habituation task was administered in a household setting.