Experiment 5 was identical to Experiment 3 in that there was both an LOP manipu- lation and a perceptual match-mismatch manipulation. It differed from Experiment 3 in that participants were required to make confidence-rating responses within a short window following presentation of each test word.
4.5.1
Methods
Participants
Fifty-three University of Missouri students participated in Experiment 5 in return for credit toward a course requirement.
Stimuli
Stimuli were the same 480 words used in Experiment 3, presented visually throughout the experiment.
Procedure
The study session in Experiment 5 was identical to that used in Experiment 3. Par- ticipants either counted the number of vowels in each study word (shallow LOP condition), or generated a word that was related to each study word (deep LOP condition). Each study word was also presented in lowercase-red, or uppercase-blue. At test, half of the studied words were presented in the same case/color as at study (perceptual match) or the opposite case/color (perceptual mismatch). Each test trial began with a fixation cross. Following 500 ms of fixation, a test word appeared. After 500 ms, “****” was presented below the test word. Participants were instructed to
respond as soon as possible, after the “****” appeared. If the response was made before the “****” appeared, a low-pitched error tone (buzz) sounded, followed by the message “Too Fast, Respond after ****”, presented for 3 seconds. If the response was made more than 500 ms after the “****” appeared, the same low-pitched error tone sounded, followed by the message “Too Slow, Response Faster!!!”, also presented for 3 seconds. Thus, participants had to respond within a window from 500-1000 ms after the test word was presented. For comparison, in Experiment 3 the average re- sponse time was 1.97 seconds, and the 25th percentile was 1.05 seconds. Thus, the 500-1000ms window should allow ample time to make a confidence rating response, but not allow for much deliberate reflection upon whether a word had been studied or not.
Prior to the study phase, participants completed two training phases to get them acquainted with the response window and test instructions. First, participants were given test trials with “WORD” serving as the stimulus. They were instructed to make any of the 6 confidence ratings as quickly as possible after the “****” appeared. They had to make their response within the correct response window 15 times in a row before moving on (most participants had no problem doing so after making a few “too slow” errors). Next they completed a practice study-test phase with a 10-item test list, before moving on to the study phase.
4.5.2
Results
Responses that were made outside of the response window (13%) were discarded. A crude measure of accuracy was constructed as for previous experiments. Doing so reveals that overall accuracy for five participants was near or below chance (d0 < .01) indicating a failure to follow instructions, and so their data were not considered in analysis. ROC curves for each condition (averaged over participants and items) are shown in Figure 4.10A. The crude d0 values for each participant were subject to a 2x2
0.0 0.4 0.8
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False Alarm Rate
Hit Rate ● ●● ● ● ● ●● ● ● ● ● mismatch−shallow match−shallow mismatch−deep match−deep
A
● ● 0.0 0.5 1.0 1.5 2.0 0.0 0.4 0.8 Familiarity (d') RecollectionB
Figure 4.10: Results from Experiment 5. A. ROC curves for each condition. B. Estimates of recollection for each condition plotted as a function of estimates of familiarity (d(s)k − d(n)k ) for each condition.
mixed-effects ANOVA with LOP condition and match-mismatch condition serving as factors. As in Experiment 3, although the effect of match-mismatch was small, the ANOVA revealed main effects of both match-mismatch (F (1, 47) = 5.69, p < .05) and LOP (F (1, 47) = 109.96, p < .05), but no interaction between the two (F (1, 47) = 0). To determine the effect of response speeding on the match-mismatch effect, the match-mismatch effects (as measured with the binomial d’ value) may be compared across the un-speeded (Experiment 3) and speeded (Experiment 5) conditions. Com- paring the mean match-mismatch effect for participants in Experiment 3 (.10) with those from Experiment 5 (.06) reveals that there is no significant difference between them (t(96) = 1.02,p = .31).
The hierarchical dual-process model was fit to the data with the R package HBMEM. Figure 4.10B shows estimates of recollection for each of the four conditions as a func- tion of estimates of familiarity d0. Because according to the dual-process model speed- ing should affect mostly recollection, and the LOP effect should be in recollection, there should be no effect of LOP in the speeded conditions. Figure 4.10 shows that
there is some effect of LOP, however, the magnitude of this effect is greatly attenuated when compared with the un-speeded conditions of Experiment 3. The remaining ef- fect of LOP appears to be in both recollection and familiarity, however, it is not clear that either of these differences are significant. The small match-mismatch effect again appears to manifest only in familiarity, as predicted by the dual-process model. As in Experiment 3, however, this effect is too small to make reliable claims about selective influence. It is, however, interesting that in four of the four conditions tested, the small match-mismatch effect is seen only in familiarity.
Figure 4.11 shows estimates of recollection as a function of familiarity for Exper- iments 1, 3 (un-speeded), and 5 (speeded) collapsed over match-mismatch condition. Whereas the dual-process model predicts that the effect of speeding should be pri- marily in recollection, speeding seems to affect both recollection and familiarity. It is, however, possible that the response window was so short as to not only degrade the recollection process, but perhaps also did not allow participants enough time to make responses based on familiarity. The critical question is whether all of the explored effects (LOP, match-mismatch, and response speeding) manifest in both recollection and familiarity, such that a line may be drawn through the 2-dimensional space re- ducing it to one dimension. If so, then this reduction is evidence that the dual-process model is over-specified. Across these three experiments, a monotonically-increasing line may be drawn that encompasses each of the nine conditions. One such line is shown in Figure 4.11. Although this simple line is not completely encompassed by all credible intervals, it is close, and a more complex line exists that could do so and yet retain monotonicity.
4.5.3
Discussion
The results of Experiments 1, 3, and 5 do not provide evidence in favor of the dual- process model. The effects of the LOP manipulation, and speeded vs. un-speeded
● ● 0.0 0.5 1.0 1.5 2.0 0.0 0.2 0.4 0.6 0.8 1.0 Familiarity (d') Recollection ● ● Fast−Shallow Fast−Deep Slow−Shallow Slow−Deep Exp. 1
Figure 4.11: DPSD estimates from Experiments 1, 3, and 5. Estimates of recollection for each condition are plotted as a function of estimates of familiarity, averaged across match-mismatch conditions. The line is the function R(d) = .2 ∗ d4+ .05, which was simply fit by hand.
response deadline conditions were both large. Both effects, however, were present in both recollection and familiarity. The result is that recollection and familiarity pa- rameter estimates trace out a 1-dimensional curve in Figure 4.11 that is characteristic of a single-process model.
The line in Figure 4.11 implies a single-process model. It is possible, however, that conditions exist with parameters that lie off the common 1-dimensional line, but I have simply not found them yet. Experiment 6 is an effort to find such a condition. Looking at Figure 4.11 it is clear that the existence of any condition that has low familiarity but high recollection would violate the current 1-dimensional nature of the space. In ROC space, such a condition would be a nearly straight line that lies
substantially off of the diagonal. Although to my knowledge such data have only been observed in a working memory task (Rouder, Morey, et al., 2008), one plausible way to achieve such a condition is to increase the amount of recollection in Experiment 5 without affecting familiarity. Although not shown in the Yonelinas (2002) review, one purported way to selectively affect recollection is to vary the length of the study (and test) list (Yonelinas, 1994). Increasing the number of studied items increases inter- item interference. According to the dual-process model, such interference should only affect recollective processes, as familiarity is automatic and operates independently of other storage processes (Yonelinas & Jacoby, 1994). In Experiment 6, Experiment 5 is replicated but with a shorter study list. The dual-process model predicts that this effect should be solely in recollection. If such selective influence in achieved, then these conditions will lie in the upper-left part of Figure 4.11, thus violating the uni-dimensionality of the space.