A thesis submitted in partial fulfilment of the requirements of the University of Wolverhampton for the degree of Doctor of Philosophy.Any form of post-encoding distraction, known as Nonspecific Retroactive Interference (NRI), may cause forgetting (Keppel, 1968; Wixted, 2004). However, recent experiments have not always found evidence for NRI and its effect may be very mild. NRI was tested across five experiments which aimed to take the epistemological approach of cognitive memory and forgetting research, and to incorporate the educational psychology domain of motivated learning through interest development. This enabled the exploration of factors which may affect NRI based forgetting, including wakeful rest, mind wandering (MW), and various forms of interest. Verbal memory was tested within a short-term (five-minute retention intervals) learning and recall setting by comparing conditions where NRI (usually elicited by spot-the-difference tasks) was present or absent. This project carefully manipulated the role of prior-tasks, measurements of interest and MW (depending on conceptualisation), and the NRI task. As a result, the thesis was able to explore the role of fatigue vs. cumulative similarity interference, the reliability of NRI effects, and provide a cognitive explanation of interest-based learning. The results demonstrated that (1) overall effects of NRI were more reliable than first hypothesised. (2) Interest is separate from NRI within this paradigm as it increases recall during the encoding phase, with interesting facts being retained more, but experiencing a similar susceptibility to interference as less interesting facts. (3) Subjective interest increases recall, with dispositional individual interest modulating the amount of situational interest evoked by the stimuli. (4) MW decreases recall but any interaction with interest requires further exploration. (5) Recall was consistently worse if the NRI condition was late-occurring, and there was limited evidence for a fatigue explanation. It is put forward that NRI is a low-level form of diversion interference which can accumulate with similarity-based PI, and potentially cognitive load
