Differential attack frequency during hypothalamic stimulation.

Slaybaugh et al. explain that they have reanalyzed the data and have discovered that John Q. got a total of 80 hits while Willie Mays got only 50 and that they therefore question my conclusions. This may seem absurd, but the argument has no more validity in their comment than it does in this example. 2) There is exceptionally poor recall in this experiment. This is not the case. Recall is only slightly poorer than that seen in normal free recall experiments with similar presentation rates. Per word recall probabilities for 20-word lists in previous experiments has usually been close to .20 (for words retrieved from long-term memory-that is, prior to the recency region). The difference between this value and .12 may seem sizable but a normal free recall procedure, which I performed with the identical subject population as the delayed free recall experiment, gave a probability of only .137 for words in nonrecency regions of 20-word lists. Thus, recall in the DFR experiment is not out of line with that in normal free recall experiments. Perhaps Slaybaugh et al. object to the fact that most subjects simply recall fewer words from long-term memory than they would like, in all free recall experiments. 3) Short-term recall is somehow implicated in the retrieval shown, since the total words recalled is within the short-term memory span. Exactly the opposite is the case. It is generally established that short-term recall is reflected in the recency effect: the enhanced recall for the last words presented in a list. But, as seen in the graphs in my report, the recency effect was eliminated by the delayed recall procedure, thus demonstrating that no recall was occurring from short-term memory, and all retrieval was long term. Surely it is not surprising that the intervening list and recall period, which were always interpolated between presentation and recall of a given list, would cause short-term retrieval to be eliminated. 4) Effects of list length are unclear because subjects might be paying attention to fewer words in the longer lists, thus seeming to reduce per word recall. Unfortunately for this explanation, subjects did not know at the start of a list what length that list would be. Thus subjects could not have treated the first five words in the 20-word lists differcntly from the first five words in the five-word lists. Yet the curves in my report (and in all papers showing the list length effect) clearly demonstrate huge differences in recall for the first five positions between the short and long lists. Of course, the explanation of Slaybaugh et al. would still be appropriate if subjects somehow divined what length each list was going to be. Perhaps their comment would be better titled "Retrieval Failure or ESP." I do not wish to give the impression that the conclusions suggested in the original paper are absolutely verified by that experiment. This is far from the case, since much additional work needs to be done. But the above objections are surely not the ones on which those conclusions must stand or fall. RICHARD M. SHIFFRINRockefeller Uniiversity, New York 10021