Working memory and its components are among the most determinant factors in human cognition. However, in spite of their critical importance, many aspects of their evolution remain underinvestigated. The present study is devoted to reviewing the literature of memory studies from an evolutionary, comparative perspective, focusing particularly on short term memory capacity. The findings suggest the limited capacity to be the common attribute of different species of birds and mammals. Moreover, the results imply an increasing trend of capacity from our non-human ancestors to modern humans. The present evidence shows that non-human mammals and birds, regardless of their limitations, are capable of performing memory strategies, although there seem to be some differences between their ability and that of humans in terms of flexibility and efficiency. These findings have several implications relevant to the psychology of memory and cognition, and are likely to explain differences between higher cognitive abilities of humans and non-humans. The adaptive benefits of the limited capacity and the reasons for the growing trend found in the present study are broadly discussed.

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The overarching role of working memory, its characteristics, and functions in our cognitive system is conspicuous. Nevertheless, sex differences in digit span as an index of the phonological loop - one of the main components of the working memory system - remain puzzling. In spite of numerous attempts, the previous studies yielded inconsistent results. The focus of this article was to study potential sex differences in verbal forward digit span. To this end, a sample of 120 young adults ranging from 16 to 25 years old from Persian population was measured and the memory span scores were analyzed using the classical method of comparing the mean score as well as the relatively new method of comparing the frequency of extreme performances. Similar to some previous studies, no significant difference was observed between males and females’ mean score. However, analyzing the frequency of extreme scores revealed that females were slightly overrepresented in the lower tail of the score distribution. Considering the evidence observed in the present study and other similar works, it is very likely that sex differences in performing memory strategies, but not in the true size of short term memory, are the underlying reasons of the observed differences. The theoretical implications and practical importance of these findings are broadly discussed.

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A Book Review on Evolution of the Learning Brain: Or How You Got to Be So Smart.. .