Cryptomnesia, also known as unintentional plagiarism, is a memory illusion in which an individual mistakenly believes that he or she created a new idea, while in actuality they simply remembered a previously experienced idea which they misattributed to themselves. Since some of the previous studies of this phenomena discovered in what ways does source similarity by sex affect cryptomnesia, the goal of this study is to discover whether cryptomnesia occurs if source similarity is more subtle and not readily apparent percieved similarity in creative thinking. The study included 61 participants, all female psychology students of Faculty of Humanities and Social Sciences in Rijeka, aged from 19 to 23 years. Analysis revealed no significant differences in cryptomnesia between participants in the high similarity group and no similarity group. However, subjects in groups which contained mostly participants from the same year of study were significantly worse at recognizing their own ideas when compared to subjects in groups which contained students from mixed years of study. Participants plagiarized significantly more during the generate-new phase, than during recall-own phase. Those participants which had more plagiarisms, also had more self-plagiarisms. Participants had very high confidence for plagiarized answers during a recognition test, a finding which is inconsistent with other studies who tested confidence during a recall test. Possible reasons for this include the inability to activate cues necessary for recall, partial forgetting of own ideas, and/or incorrect relearning of an idea during the generate-new phase.