Hockenbury Discovering Psychology 5th txtbk

234 CHAPTER 6 MemoryGeorge Sperling Sperling carried out hisresearch on the duration of sensorymemory while still a graduate studentat Harvard. Now at the University ofCalifornia–Irvine, he continues to studyperception, attention, and cognition.Figure 6.2 Sperling’sExperiment Demonstratingthe Duration of SensoryMemory In George Sperling’s(1960) classic experiment, (1)subjects stared at a screen onwhich rows of letters were projectedfor just one-twentieth ofa second, then the screen wentblank. (2) After inter vals varyingup to one second, a tonewas sounded that indicatedthe row of letters the subjectshould report. (3) If the tonewas sounded within aboutone-third of a second, subjectswere able to report the lettersin the indicated row becausethe image of all the letters wasstill in sensory memory.1.Letters are displayed ona screen for 1/20 of asecond, then the screengoes blank.You were able to answer the question because your sensory memory registered andpreserved the other person’s words for a few fleeting seconds—just long enough foryou to recall what had been said to you while your attention was focused on themovie. Sensory memory stores a detailed record of a sensory experience, but onlyfor a few seconds at the most.The Duration of Sensory MemoryIt Was There Just a Split Second Ago!The characteristics of visual sensory memory were first identified largely through theresearch of psychologist George Sperling in 1960. In his experiment, Sperlingflashed the images of 12 letters on a screen for one-twentieth of a second. The letterswere arranged in four rows of 3 letters each. Subjects focused their attention onthe screen and, immediately after the screen went blank, reported as many letters asthey could remember.On average, subjects could report only 4 or 5 of the 12 letters. However, severalsubjects claimed that they had actually seen all the letters but that the completeimage had faded from their memory as they spoke, disappearing before they couldverbally report more than 4 or 5 letters.On the basis of this information, Sperling tried a simple variation on the originalexperiment (see Figure 6.2). He arranged the 12 letters in three rows of 4 letterseach. Then, immediately after the screen went blank, he sounded a high-pitched,medium-pitched, or low-pitched tone. If the subjects heard the high-pitched tone,they were to report the letters in the top row; the medium-pitched tone signaledthe middle row; and the low-pitched tone signaled the bottom row. If the subjectsactually did see all the letters, Sperling reasoned, then they should be able to reportthe letters in a given row by focusing their attention on the indicated row beforetheir visual sensory memory faded.This is exactly what happened. If the tone followed the letter display in underone-third of a second, subjects could accurately report about 3 of the 4 letters inwhichever row was indicated by the tone. However, if the interval between thescreen going blank and the sound of the tone was more than one-third of a second,the accuracy of the reports decreased dramatically. By the time one second hadelapsed, the image in the subject’s visual sensory memory had already faded beyondrecall.Sperling’s classic experiment demonstrated that our visual sensory memory holdsa great deal of information very briefly, for about half a second. This information isavailable just long enough for us to pay attention to specific elements that are significantto us at that moment. This meaningful information is then transferred fromthe very brief storage of sensory memory to the somewhat longer storage of shorttermmemory.Length oftime variesup to onesecond.2. Tone is sounded,indicating row.3.Subject reportsletters in rowindicated by tone.