Psychological essentialism is ubiquitous. It is one of primary bases of thoughts and behaviours throughout our entire lifetime. Human's such characteristics that find an unseen hidden entity behind observable phenomena or exemplars, however, lead us to somehow biased thinking and reasoning even in the realm of science, including psychology. For example, a latent variable extracted from various measurements is just a statistical property calculated in structural equation modeling, therefore, is not necessary to be a fundamental reality. Yet, we occasionally feel that there is the essential nature of such a psychological construct a priori. This talk will demonstrate examples of psychological essentialism in psychology and examine its resultant influences on working memory related issues, e. g., working memory training. Such demonstration, examination, and subsequent discussions on these topics will provide us an opportunity to reconsider the concept of working memory.