George Sperling

Career

In summer 1958, Sperling went to work at Bell Laboratories where numerous experiments were conducted. Sperling was originally attracted to psychology because he wanted to apply quantitative methods and theories used by physicists to describe the brain's mental microprocesses.

In the early 1960s, George Sperling proposed a method of measuring visual persistence duration, an auditory synchronization method of measuring visual persistence duration. This approach had the synchrony of a click and the onset/termination of a light, this synchrony being judged by the subject. Later the method was innovated by with Erich Weichselgartner so that the entire rise and fall of the temporal brightness function was also measured, contrasting the initial method that only measured the moment and which visual persistence stopped.

Throughout Sperling's career, he has contributed very much to the fields of visual information processing and theory and empirical research. In 1960, Sperling performed an experiment using a matrix with three rows of three letters. Participants of the study were asked to look at the letters, for a brief period of time, and then recall them immediately afterwards. This technique, called free recall, showed that participants were able to, on average, recall 4–5 letters of the 9 they were given. This however, was already generally accepted in the psychological community, because it was understandable that people simply could not retain all the letters in their mind in such a brief period of time. Sperling, on the other hand, felt that they had encoded all of the letters in their mind, but had simply forgotten them while trying to recall this information on what they had seen. He believed that all nine letters were stored in the viewer's memory for a short period of time, but the memory failed leading to only 4 or 5 being recalled. Sperling called this iconic memory. This was exemplified through Sperling's Iconic Memory Test, which involves having a grid of letters being flashed for 1/20 of a second. If individuals were prompted to recall a particular row immediately after the grid was shown, opposed to being asked to recall the entire grid, participants experienced higher accuracy. This procedure demonstrated that although iconic memory can store the whole grid, information tends to fade away too rapidly for a person to recall all of the information. Sperling also showed this with his experiment of cued recall. This trial was similar to free recall; however, instead of allowing participants to recall any of the letters, it would allow them to view the same matrix for the same amount of time, and then hear a pitch corresponding to a different row in the matrix. The viewer was to recall the letters in that corresponding row. On average, viewers were able to recall more during cued recall trials than free recall.

Sperling built upon this experiment to then determine the amount of time before information was discarded from a person's memory. Using the same matrix, allowing viewers to see the matrix for the same amount of time, and still giving the pitches to cue the viewer which row to recall, Sperling added a twist: there would be a 5-millisecond delay after the letters disappeared before the cue would appear. The participants were unable to recall as many letters, thus showing that visual stimuli that are not added to short-term memory are discarded less than 5 milliseconds of initial introduction. (It was later agreed upon that most visual icons are eliminated from memory before 250 milliseconds.)

Sperling has lectured at Stanford University, University of Washington, University of Western Australia, University of London, University of California: Los Angeles, Columbia University, Duke University and New York University. He was elected a Fellow of the American Academy of Arts and Sciences in 1992.