No one has had more effect on how human experimental psychology is done than Saul Sternberg, a retired professor of psychology at the University of Pennsylvania. In the 1960s he introduced a memory-scanning task in which the subject responds as quickly as possible whether a probe item (usually a digit) is on a short memorized list. The main measure was reaction time (RT) — the time between when the subject saw the item and his response (”yes” or “no”). The linearity of the RT-vs-set-size function and the equality of the “yes” and “no” slopes suggested that search of the memorized list was serial and exhaustive (exhaustive meaning that the whole list was searched even when the target was found before the end). Before this heavily-cited work (published in Science and American Scientist), RT experiments were rare; after it, they were common.
SR: Where did your first ideas about research design come from?
SS: While I was a graduate student [(at Harvard in the 1950s)] I read Williams James’ Principles of Psychology, which increased the curiosity I had developed about mental processes from my introspections. Although I wasn’t working on those questions when I was a grad student, I became interested in them. I wrote down ideas for experiments — experiments on short-term memory, for example. Experiments to answer questions about things I observed about my mental processes while engaged in writing and reading and other everyday activities. At the time I was doing theoretical work on learning models that apply to both animals and people. [Stochastic Models for Learning by Bush, Sternberg’s advisor, and Mosteller was published in 1955.] I didn’t collect much data as a graduate student, after my interests turned to learning models. Earlier I had collected data in social psychology. I recall putting a lot of effort into an experiment on small group interactions. What was novel was that we were recording interaction events in real time by punching IBM cards.
I learned how to be an experimental psychologist during my first teaching appointment that started in 1960 at Penn, when I co-taught a laboratory course on experimental psychology. I taught it with Bob Teghtsoonian and Jack Nachmias, who became my teachers. In those days, many students took a lab course after Psych. 1. The course required us to develop experiments for undergraduates to do. Questions that arose in those experiments went beyond available knowledge. And these questions led to some actual research. In 1962 Bob Teghtsoonian and I gave a paper at EPA on all-or-none versus gradual learning of response components, in which we reported tests of two models. And in 1963 Jack Nachmias and I gave a paper at the Psychonomic Society in which we reported our application of signal detection theory to data on recognition memory that we had collected.
SR: You started your memory-scanning experiments after that course?
SS: That’s true. I started them during my second year at Penn. I was still working on learning models. I was also supervising a graduate student whose research had to do with short-term memory. Not RT experiments, however. What got me interested in RT experiments was work by Ulric Neisser measuring search times. He measured visual search times as a function of number of targets for which you search. [Neisser’s subjects searched a visual display — e.g., of digits or letters — for the presence of one or more digits or letters. The main measure was how long it took to search the whole display.] It’s like a crude RT experiment. You’re not measuring how long it takes to make one decision, you’re measuring the time to make many decisions. I was skeptical about his conclusions so I thought it would be worth measuring how long it took to make a decision about one visual item. That led to the memory-scanning experiments. I did several of them, to help choose among alternative interpretations, before I reported the results. I gave a paper on those experiments at the meeting of the Psychonomic Society during the summer of 1963.
Previous post in this series: Brian Wansink on research design.