Subject: Is time-shrinking a new illusion ? From: Yoshitaka Nakajima <nakajima(at)KYUSHU-ID.AC.JP> Date: Tue, 15 Mar 1994 13:44:27 JSTDear Colleagues, I learned that some of my colleagues are interested in whether my coworkers and I are prepared to take a reaction against the criticism (in P&P) on our articles, where we reported a 'new' phenomenon which we call 'time-shrinking'. Suppose that two neighboring empty durations marked by three sound bursts have physical durations of 50 ms and 120 ms (in this order). The second duration is extremely underestimated (The PSE is about 70 ms, showing an underestimation of 40 %). The point of the criticism is that this phenomenon is not novel because this is 'just' a sort of positive time-order error. We reacted, actually, and our reply was not accepted, partly due to my poor language maybe. We decided that the best thing we can do now is to publish the data we have gathered as quickly as possible in order to show the curious nature of this phenomenon. Before doing this tough job, I would like to summarize some points of our (almost rejected) reply: 1) No previous data or theories could predict such a systematic, stable and big effect of so simple a temporal context on duration perception. Tendencies found in studies of time-order errors or related materials are rather inconsistent. If an unpredictably clear tendency is established in this almost chaotic situation, it should at least be recognized as a step to a new finding. 2) Even when a mathematical equation has proved useful to describe experimental results obtained in a particular paradigm, we often have to choose several parameter values for each experimental condition which fit the empirical data, and people often forget that this procedure also makes an 'ad hoc' explanation. We do not think time-shrinking could be derived from previous theories. (This is the point where we are having trouble. It seems logically impossible to prove that these 'methematical' models 'cannot' predict the phenomenon.) 3) Time-shrinking disappears suddenly when the difference between the first and the second duration exeeds about 100 ms, and this tendency is constant even when the first duration is varied between 40 ms and 280 ms. This clear, but peculiar, tendency is difficult to derive from conventional studies of time-order errors. 4) In most studies of time-order errors, inter-duration intervals above 500 ms are used, and it seems difficult to relate the experimental data obtained in such conditions directly with the data of our previous experiments, where the inter-duration intervals were 0 ms. We have a set of unpublished data (which we presented in Bourges, France, in 1992) showing that the underestimation of the second duration suddenly increases when the inter-duration interval becomes shorter than a certain value below 400 ms. The data suggest that the positive time-order error obtained in a conventional paradigm and our time-shrinking have different mechanisms. I would appreciate any opinions either to me directly or to this network. Best regards, Yoshitaka Nakajima nakajima(at)kyushu-id.ac.jp