Two language learning strategies have been described as common in both children and adults: fast mapping (FM), which promotes learning from context, and explicit encoding (EE), which is provided through direct instruction. Previous functional neuroimaging studies in adult learners have suggested differential neural mechanisms underlying these two major cognitive strategies, with some limited evidence in support of such differences also found in behavioural experiments. Nevertheless, the exact nature of these differences remains underinvestigated. Our goal was to explore putative differential effects of EE and FM strategies on the acquisition of novel words, with a focus on scrutinising the quality of recognition of newly learnt items. In two experiments, participants (total sample size = 82) learned 18 novel words presented ten times each in a word-picture association paradigm using EE and FM conditions. Learning outcomes were assessed immediately after the training using a recognition task. In both experiments, we found no differences in either the accuracy or the reaction time of word recognition between FM and EE conditions, which suggests similar behavioural efficiency of both strategies. However, we found a negative correlation between reaction time and response accuracy in recognising the words learned through EE, with no similar effects for FM, which indicates qualitative differences in underlying memory traces formed via these two acquisition modes. These results can be seen to imply that people tend to use information acquired through EE more confidently than that acquired through FM.