400
In Sperling's memory experiment subjects were shown three rows of three letters followed immediately by a low, medium, or high pitched tone. The subjects were able to report
A. all three rows with perfect accuracy each time a tone was presented
B. only the top row of letters whatever tone was presented
C. only the middle row of letters whatever tone was presented
D. any one of the three rows of letters, depending on which tone was presented
What is
D. any one of the three rows of letters, depending on which tone was presented