Approved For Release 2000/08/08 : CIA-RDP96-00789R002200600001-1 Table 1 Results of Monte Carlo Calculation for RMS Phase 06/24/88 08/25/88 08/26/88 10/19/88 0.513 1.491 0.423 0.305 0.358 1.405 1.852 1.011 0.619 1.259 03/29/89 03/29/89 05/23/89 05/24/89 05/25/89 05/24/89 05/25/89 ba Ba ANP NDA NY AN DH The p-values shown in Table 1 are all single tailed (i.e., the area in the upper tail). Because the distribution of means is approximately normal, we have converted the empirical p-values to their respective two-tailed z-scores. If the p-value was less than 0.5, the z-score shown in Table 1 was computed from the inverse normal distribution assuming a p-value twice the one shown. If the p-value was more than 0.5, we subtracted it from 1.0, doubled the result, and computed the z-score as above. To test the null hypothesis that the combined RS phase shifts are characteristic of the data, we computed a standard Stouffer’s Z (Zs) for the 11 sessions shown in Table 1. There is statistical evidence that the data within + 0.5 seconds of the RS are not characteristic of the data at large (Zs = 1.99, p < 0.024, effect size = 0.599). Similarly, the combined statistic for the PS indicates that these data are also not characteristic (Zs = 2.92, p < 0.002, effect size = 0.924). Therefore, there appears to be some statistical anomaly associated with the RMS phase shifts for both stimuli types. Cc. Results: Button Presses In the early SRI study®, significant changes in alpha production were observed in response to an RS. The statistical evidence, however, did not indicate that the viewer was able to recognize an RS cognitively (i.e., the viewer’s button presses relative to the RS did not exceed mean chance expectation). 20 Approved For Release 2000/08/08 : CIA-RDP96-00789R002200600001-1
Approved For Release 2000/08/08 : CIA-RDP96-00789R002200600001-1 In the current experiment, viewers 002, 009, and 372 were asked to press a button whenever they “perceived” an RS. The total number of stimuli during a session of 10 runs was not known in advance because of the randomization procedure. The null hypothesis is that the probability of a time interval having a stimulus is the same for those intervals with a button press as for those without a button press. In other words, the presence or absence of a stimulus is independent of the presence or absence of a button press. We tested this null hypothesis to determine if a viewer is cognitively aware of the RS. In Table 2, the fractional hitting rate is p, = A/(A+B), and the fractional missing rate is P2= C/(C+D). The total number of 1-second intervals is N = (A+B+C+D), and the total stimulus rate is po = (AtC)/N. Table 2 Data Schema for Interval Conditions Stimulus _ ie ar wise Pe Te | Then the following statistic is approximately normally distributed with a mean of 0 and a variance of 1 under the null hypothesis: (p1 - P2) z= . Po(1 ~po)( was + aa) Table 3 shows N, Po, P1, Pz, Z, p-value, and the effect size, 7, for the three sessions for which button-press data were collected. As in the earlier SRI study, there is no indication that the viewers were cognitively aware of the RS. Table 3 Button Pressing Results _ Viewer 002 . 0.198 0.164 009 . 0.068 0.094 372 . 0.119 0.160 21 Approved For Release 2000/08/08 : CIA-RDP96-00789R002200600001-1
Approved For Release 2000/08/08 : CIA-RDP96-00789R002200600001-1 IV DISCUSSION AND CONCLUSIONS We have found statistical evidence that the relative phase shift from -0.5 to 0.5 seconds of an RS are not characteristic of the data at large (Zs = 1.99, p < 0.024, effect size = 0.599). The combined statistic for the PS indicates that the relative phase shift from -0.5 to 0.5 seconds of a PS are also not characteristic of the data at large (2: = 2.92, p < 0.002, effect size =0.924). Averaged across all viewers, the magnitude of the results, as indicated by their effect sizes of 0.599 and 0.924, respectively, is considered robust by accepted behavioral criteria defined by Cohen.9* A. Root-Mean-Square Phase Searching for a change of phase asa result of an RS is a natural extension of results quoted in the literature. For example, Rebert and Turner§ report an example of photic driving (i.e., an extreme example of phase locking) at 16 Hz. In their work, a subject was exposed to a 16-Hz visual DS randomly balanced with no stimulus during 4-second epochs. The average power spectra showed approximately 10-Hz alpha activity during the no-light epochs, and a strong 16-Hz and no 10-Hz peak during the 16-Hz epochs. One interpretation of their result is that the alpha rhythm was blocked, and the CNS “locked” on to the flashing stimulus. Eason, Oden, White and White,'° report a phase-shift phenomenon when a rare stimulus, which is random relative to the internal alpha activity, is presented as a DS: « ..when a stimulus flash is presented, the resulting primary evoked response acts as a trigger stimulus which temporarily synchronized a certain percentage of the neural elements normally under the influence of an internal pacemaker. Desynchronization of the elements participating in the evoked response would occur ‘as the elements are brought back under the influence of an internal pacemaker or are affected by neurons not involved in the response.” In other words, the internal alpha is momentarily interrupted by an external stimulus, and, in the absence of continuing external stimuli, returns back to its original frequency, but at a random phase relative to its pre-stimulus state. To understand what would be expected in our experiment for the distribution of RMS phases during the Monte Carlo simulations, we examine a hypothetical case. Suppose that the * Values of 0.1, 0.3, and 0.5 correspond to small, medium, and large effects, respectively. 22 Approved For Release 2000/08/08 : CIA-RDP96-00789R002200600001-1