Experiment 8: Immediate Serial Recall Task with Proactive Interference

& Tehan, 2002)

In Experiment 4, the relationship between the letter-crossing and target recall in a pro-active interference task was examined. Overall, immediate serial recall performance and re-call of a specific target item (i.e., Block-1 or Block-2 targets) in each list were highly corre-lated. In this experiment, the analyses have been restricted to target specific recall, as the Block-2 target measure details interference of the proactive to-be-forgotten foil, compared to Block-1 targets with no proactive interference conditions. The outcomes of Experiment 4 in-dicated that letter-crossing accuracy was related to PI-ISR target recall and thus it is expected that accuracy group differences should be present in the current experiment. As in the prior

experiments, a significant group by session interaction serves as a functional marker of the strength model.

On the post-test measure, a manipulation was added to enhance the likelihood that the foil would be recalled instead of the target item on the Block-2 trials, as detailed in the meth-ods section. If this manipulation is successful, then any benefits of repetition that have been observed in earlier experiments may be reduced under block-2 target recall and there should be a marked increase in foil intrusions. Experiment 8 reported strong power, N = 114, α = .05, β = .01, Power = .99, with a critical F value of 3.07.

6.7.1. Method.

The participants, materials, and procedure were described in Experiment 4. There was one change to the post-test PI-ISR task that was made to increase the number of block-1 foils that were produced. Tehan and Humphreys (1998) demonstrated that if rhymes of the foil were included as filler items in the second block, target recall decreased and recall of the block-1 foil increased. Consequently, in all the post-test two-block trials, the first and fourth filler items in the second block were replaced by rhymes of the foil. Thus an example of a trial would be, bed tea white heart ! kite cat black site 56 ?????, where kite and site were priming the foil white.

6.7.2. Results.

The analyses conducted were a 3 x (Group: Higher, Moderate, and Lower perfor-mance) x 3 (Items: Block-1 Targets, Block-2 Targets, and Foil items) x 2 (Session: Pre-test, Post-test) mixed design ANOVAs for letter-crossing accuracy, speed, and slope group splits.

A 2 (Group: Distractors, No-Distractors) x 3 (Items: Block-1 Targets, Block-2 Targets, and Foil items) x 2 (Session: Pre-test, Post-test) mixed design ANOVA was conducted for the distractor group split. Generally, performance on all measures were higher on the post-test than pre-test. This means that target recall improved, but there was also an increase in foil in-trusions. Where any variable violated Mauchley’s test of sphericity, the Huynh-Feldt correc-tion was used, as ɛ > 0.75. The results of the experiment are summarised in Table 6.4 and Figure 6.4.

Table 6.4

Mean and Standard Errors for Letter-Crossing Accuracy, Speed of Completion in Minutes, Slope of Accuracy Over Time, and Distractor Recalls Split By Letter-Crossing Performance Groups (Higher, Moderate, and Lower) Across Pre- and Post-Test Sessions in Block-1 Tar-gets, Block-2 TarTar-gets, and Foil items under the PI-ISR Task (Tehan & Tolan, 2002)

PI-ISR Task

Block-1 Targets Block-2 Targets Foils

Figure 6.4. Mean accuracy (y axis) scores across pre- and post-test sessions (x axis) for PI-ISR task (Tolan & Tehan, 2002) items: Block-1 Tar-gets, Block-2 TarTar-gets, and Foils. Error bars were created from standard error values. Whereby Higher performance refers to Higher Accuracy,

Block-1 Targets Block-2 Targets Foils

Faster Speed, Minor Slope, and No-Distractors; Moderate performance refers to Moderate Accuracy, Moderate Speed, Moderate Slope; and Lower performance re-fers to Lower Accuracy, Slower Speed, Major Slope, and Distractors.

6.7.2.1. Accuracy split. There were significant differences between ac-curacy groups, F (2, 111) = 4.62, p = .012, MSE = .12, partial η² = .08, where the higher accuracy group reported higher ratings of targets and lower foil intrusions, compared to moderate and lower accuracy groups respectively. A main effect for ses-sion was found, F (2, 111) = 5.35, p = .023, MSE = .02, partial η² = .05. Perfor-mance improved from pre- to post-test. There was no interaction between session and accuracy groups, F (2, 111) = 1.23, p = .30, MSE = .02, partial η² = .02. The items effect was significant, F (2, 222) = 399.90, p <.001, MSE = .06, partial η² = .78, with greater recall under block-1 targets, followed by block-2 targets and foil intrusions respectively. There was an interaction between items and accuracy group, F (4, 222)

= 5.38, p <.001, MSE = .06, partial η² = .09. Planned contrasts revealed a significant quadratic interaction, F (2, 111) = 7.37, p = .001, where greater recall was evident under the higher accuracy group, compared to moderate and lower accuracy groups.

Group differences were least obvious in the recall of block-1 targets and more pro-nounced in the block-2 measures. No other interactions were found.

6.7.2.2. Speed Split. There was no significant difference between groups, F (2, 111) = .52, p = .60, MSE = .13, partial η² = .01, with the moderate speed group reporting only slightly greater target rates than faster and slower speed groups respectively. The faster group reported slightly greater foil intrusions than moderate and slower speed groups respectively. There was a main effect for session, F (1, 111) = 4.55, p = .035, MSE = .02, partial η² = .04. An improvement in perfor-mance was observed from pre- to post-test. There was no interaction found between session and speed groups, F (2, 111) = 1.81, p = .169, MSE = .02, partial η² = .03.

The items effect was significant, F (1.92, 212.71) = 382.17, p <.001, MSE = .06, par-tial η² = .78, with greater recall under block-1 targets, followed by block-2 targets and foil intrusions respectively. No other interactions were observed.

6.7.2.3. Slope split. There was no significant difference found be-tween slope groups, F (2, 111) = .21, p = .814, MSE = .13, partial η² < .01, where the moderate slope group reported slightly greater target and foil rates than minor and major slope groups respectively. There was a main effect for session, F (1, 111) = 6.12, p = .015, MSE = .02, partial η² = .05, where performance increased from pre-

to post-test. There was no interaction between session and slope groups, F (2, 111) = .32, p = .726, MSE = .02, partial η² = .01. The items effect was significant, F (1.92, 213.14) = 369.55, p < .001, MSE = 23.78, partial η² = .77, with greater recall under block-1 targets, followed by block-2 targets and foil intrusions respectively. No other interactions were found.

6.7.2.4. Distractor split. There was a significant difference between the distractor groups, F (1, 112) = 4.80, p = .031, MSE = .121, partial η² = .04, where the No-Distractor group reported greater target accuracy than the Distractor group, however, greater foil intrusions were also reported by the No-Distractor group. There was a main effect for session, F (1, 112) = 4.17, p = .044, MSE = .02, partial η² =.04. A significant increase in performance was observed from pre- to post test. There was no interaction between session and distractor groups, F (1, 112) = .26, p = .608, MSE < .02, partial η² = <.01. The items effect was significant, F (1.92, 214.93) = 361.22, p <.001, MSE = .06, partial η² =.76, with greater recall under block-1 targets, followed by block-2 targets and foil intrusions respectively. No other interactions were observed.

6.7.3. Preliminary discussion.

The manipulation of adding rhyming distractors to the second block had the desired effect in that there was only a modest increase in target recall at post-test and there was a significant increase in foil intrusions. Similar to the previous experi-ments, target recall improved from pre-test to post-test, with group differences found in the accuracy and distractor measures. Most importantly there were no group by session interactions on any of the four measures (i.e., accuracy, slope of accuracy, completion time, and distractor responses) of splitting the data. In sum, there was no evidence of depletion transfer effects on this task.