The field of psychology has emphasized quantitative laboratory research as a defining character of its role as a science, and has generally de-emphasized qualitative research and theorizing throughout its history. This article reviews some of the effects of this emphasis in two areas, intelligence testing, and learning and memory. On one side, quantitative measurement produced the widely used IQ test but shed little light on the construct of intelligence and its role in human cognition. On the other side, reductive quantification (...) and experimental constraints limited the investigation and understanding of human memory systems and complex learning throughout the first century of the field’s history. Recent research under fewer constraints has made greater progress in these areas. (shrink)