Originally Posted by
Limbo
Robin, regarding the paper by Dean Radin in your OP. I was wondering if you could highlight the specific flaws in this section:
Anticipatory strategies.
"This is the most common and prima facie the most plausible conventional explanation for the observed effects. The idea assumes the use of an experimental design with dichotomous stimuli: emotional vs. calm, or stimulus vs. no stimulus. With such a design, it is conceivable that on sequential trials the participant’s EDA would increase with each successive calm trial, since anticipation would keep increasing until the emotional trial appeared. Thus, EDA would peak on the emotional trial and then reset back to zero on the next trial, as illustrated in Figure 7.
If this strategy were followed either consciously or unconsciously, then EDA averaged across all emotional trials would be higher than EDA averaged across Fig. 7. Simulation of an idealized anticipatory strategy. The y-axis is the degree of autonomic arousal, the x-axis is successive trials. The top of each ‘‘arousal’’ ramp represents an emotional trial; all other trials are calm. Electrodermal Presentiments 269 calm trials. Simulation and analytical studies have confirmed the existence of this bias (e.g., Dalkvist et al., 2002; Wackermann, 2002). The same simulations also show that with longer sessions, or after pooling trials across many participants, that these biases can become vanishingly small. Anticipatory simulation studies are valuable in highlighting worst-case scenarios, but they also oversimplify what actually occurs in these experiments.
For example, as previously mentioned, people’s idiosyncratic responses to photos inevitably blur the dichotomous distinction between calm and emotional targets. A more realistic anticipatory simulation might use targets with a continuous range of emotionality, and it would adjust the arousal value for trial N ž 1 up or down according to the emotionality rating of trial N. But idealized simulations and strategies aside, we can investigate whether anticipatory strategies can explain the observed results by examining the actual data. To do this, data from Experiments 2 and 3 were pooled; this provided a set of 3,469 trials, contributed by a total of 103 participants. The pre-stimulus sums of SCL (i.e., PSCL) prior to stimulus onset in each of the two experiments were normalized separately and then combined.3 Then the targets were separated into two classes: emotional, defined as those trials with the top 26% emotionality ratings, and calm, defined as those 74% with lower emotionality ratings. These percentages were selected to create about a 1:3 ratio of emotional to calm targets to ensure that there would be an adequate number of calm targets in a row to test the expectations of an anticipatory strategy. Based on this definition of emotional and calm targets, 13 of the 103 participants were identified who independently obtained significant (p , 0.05) emotional vs. calm differences in their pre-stimulus responses. Together these people contributed a total of 450 trials, and as a group they represented (by selection) extremely strong evidence for presentiment.
An anticipatory strategy supposes a positive trend between the number of calm trials before an emotional trial vs. PSCL for each of those trials, as illustrated in Figure 7. Note that this trend, which can be evaluated with a simple linear correlation, cannot include the emotional trial itself, since that would confound testing an anticipatory strategy with a genuine presentiment effect. Figure 8 shows the observed means of PSCL for calm trials 1 to 13 steps before an emotional trial, and for the emotional trial itself (the ‘‘0’’ point on the x-axis), with one standard error bars. The error bars become progressively smaller because the number of sequential calm trials before an emotional trial decreases with the number of total trials. For example, there are many more cases of say, the sequence C–E (one step away) than there are of the sequence, C–C–C–C–C–E (five steps away).
The weighted linear correlation between mean PSCL and trial number for steps 13 ! 1 was positive, but not significantly so (r ¼ 0.29, p ¼ 0.17). Notice that with one exception, all of the mean PSCL values prior to the emotional trial were negative, and three were significantly negative, including the trial immediately preceding the emotional trial. Thus, contrary to the expectations of 270 D. I. Radin an anticipatory strategy, a subset of participants specifically selected for exhibiting strong differential results suggestive of a genuine presentiment effect showed relaxation responses before the emotional target rather than progressive arousal. In sum, while idealized anticipatory strategies might provide an explanation of the observed results in principle, the actual data did not indicate that such strategies were employed."
I will deal in more detail later. But why did Radin test a small percentage (only 450 trials) to test this? He could easily have tested the entire dataset. I can easily do this on my simulated dataset.
More generally, since we are all agreed that the results shown are possible without presentiment, on what basis does he regard them as evidence for presentiment?