DEVELOPMENTAL CHANGE IN PROACTIVE INTERFERENCE
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Supplemental Materials
Developmental Change in Proactive Interference Across the Life Span:
Evidence From Two Working Memory Tasks
by Sandra V. Loosli, et al., 2013, Developmental Psychology
http://dx.doi.org/10.1037/a0035231.supp
In the supplementary material, we provide further results regarding the developmental effects of
working memory (WM) and resistance to proactive interference (PI) in the recent-probes task and the
n-back task. First, we report analyses with the nonrecent trials only, which may give additional
information about the global development of WM. Second, we report ANOVAs of the “full” models
with all trial conditions (i.e., with the factors recency and probe type for the recent-probes task and
with the three conditions targets, lures, and nones for the n-back task. As in the main article, we first
report analyses within the overall sample (three age groups), which are followed by the same analyses
in the two children samples to look for more specific developmental effects during childhood.
Comparisons of all trial conditions for each age group are also provided in Figure S1 (recent-probes)
and Figure S2 (n-back).
Working Memory Performance (Nonrecent Trials)
Accuracy
Recent-probes. A repeated-measurements ANOVA with age group (children, younger adults, older
adults) as the between-subjects factor and probe type (positive and negative trials) as the withinsubject factor yielded a main effect of age group, F(2, 89) = 12.99, p < .001, ηp2 = .23, and a main
effect of probe type, F(1, 89) = 70.49, p < .001, ηp2 = .44, but no significant interaction between both,
F(2, 89) = .83, p = .44, ηp2 = .02. Negative trials were answered more correctly than positive trials,
and planned contrasts showed that younger adults performed better than older adults (p < .05) or
children (p <. 001). The difference in accuracy between positive and negative trials did not differ
between children and younger adults (p = .236) or between younger and older adults (p = .958).
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A subsequent ANOVA with the two children samples (age group as the between-subjects and probe
type as the within-subject factor) revealed a main effect of age, F(1, 40) = 40.82, p < .001, ηp2 = .51; a
main effect of probe type, F(1, 40) = 40.84, p < .001, ηp2 = .51; and a significant interaction between
probe type and age group, F(1, 40) = 5.04, p < .05, ηp2 = .11. Negative trials were answered more
accurately than positive trials, and the difference between both probe types was larger in the younger
group.
N-back. A repeated-measurements ANOVA with age group (children, younger adults, older adults) as
the between-subjects factor and trial condition (targets vs. nones) as the within-subject factor revealed
significant main effects of age group, F(2, 89) = 31.80, p < .001, ηp2 = .417, and of trial condition,
F(1, 89) = 166.20, p < .001, ηp2 = .65, and a significant interaction between both, F(2, 89) = 12.80, p <
.001, ηp2 = .22. As in the recent-probes task, negative trials (nones) were easier than positive trials
(targets). Planned contrasts revealed that younger adults performed better than older adults (p < .01)
or children (p < .001). The interaction was driven by the difference between children and younger
adults, since children showed a lower target score relative to the nones, compared with adults (p <
.001). However, this difference was equal in older and younger adults (p = .895).
A subsequent ANOVA with both children groups showed main effects of age group, F(1, 40) = 14.67,
p < .001, ηp2 = .27, and of trial condition, F(1, 40) = 144.37, p < .001, ηp2 = .78, and a marginal
significant interaction between both, F(1, 40) = 3.71, p = .061, ηp2 = .09. Nones were answered more
accurately than targets, and older children were more accurate than younger children.
Reaction Times
Recent-probes. A repeated-measurements ANOVA with age group (children, younger adults, older
adults) as the between-subjects factor and probe type (positives vs. negatives) as the within-subject
factor revealed main effects of age group, F(2, 89) = 28.84, p < .001, ηp2 = .39, and of probe type, F(1,
89) = 4.48, p < .05, ηp2 = .05, and a significant interaction between both, F(2, 89) = 3.16, p < .05, ηp2 =
.07. Reaction times in negative trials were higher than in positive trials; however, this effect was most
prominent in the older adults. Planned contrasts revealed that younger adults were faster than older
adults or children (both p < .001). The difference between positive and negative trials was marginally
higher in older than in younger adults (p = .052), but was similar for young adults and for children (p
= .855).
An ANOVA within the children showed a significant main effect of age group, F(1, 40) = 17.72, p <
.001, ηp2 = .31, whereas there was no significant effect of probe type, F(1, 40) = .064, p = .801, ηp2 =
.00, and no interaction (F(1, 40) = .90, p = .384, ηp2 = .02).
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N-back. A repeated-measurements ANOVA with age group (children, younger adults, older adults) as
the between-subjects factor and trial condition (targets vs. nones) as the within-subject factor resulted
in main effects of age group, F(2, 89) = 6.01, p < .01, ηp2 = .12, and of trial condition, F(1, 89) = 6.21,
p < .05, ηp2 = .07, but in no interaction between both, F(2, 89) = 2.02, p = .14, ηp2 = .04. Nones were
answered faster than targets. Planned contrasts revealed that in general, young adults answered faster
than children (p < .05) or older adults (p < .001). However, the difference between targets and nones
was not significant between children and younger adults (p = .115), nor between older and younger
adults (p = .507).
A subsequent ANOVA within the children samples revealed no significant main effect of age group,
F(1, 40) = 1.73, p = .196, ηp2 = .04; however, there was a significant main effect of probe type, F(1,
40) = 8.834, p < .01, ηp2 = .18. Positive trials were answered more slowly than negative trials,
particularly in the younger group, as indicated by a significant interaction, F(1, 40) = 7.50, p < .01, ηp2
= .16.
Working Memory Performance and Proactive Interference (All Trial Conditions)
Accuracy
Recent-probes task. A repeated-measurements ANOVA with recency (recent vs. nonrecent) and
probe type (positive vs. negative) as the within-subject factors and age group (children, younger
adults, older adults) as the between-subjects factors showed significant main effects of recency, F(1,
89) = 10.57, p < .01, ηp2 = .11, and probe type, F(1, 89) = 20.91, p < .001, ηp2 = .19. Nonrecents were
answered more accurately than recent trials, and negatives were answered more accurately than
positives. The main effect of age group was also significant, F(2, 89) = 26.23, p < .001, ηp2 = .37.
Planned contrasts showed that young adults were more accurate than older adults or children (both p <
.001). The interaction between recency and probe type was significant too, F(1, 89) = 40.75, p < .001,
ηp2 = .31: In the negatives, nonrecents were answered more accurately than recent trials; however, in
the positives, the opposite effect appeared, although less pronounced. The two-way interactions
between age group and each of these factors failed to reach significance: Recency  Age Group, F(2,
89) = 2.19, p = .117, ηp2 = .05; and Probe Type  Age Group, F(2, 89) = 0.36, p = .702, ηp2 = .01, as
well as the three-way interaction among recency, probe type, and age group, F(2, 89) = 1.10, p = .339,
ηp2 = .02.
A subsequent repeated-measurements ANOVA with both groups of children revealed significant main
effects of recency, F(1, 40) = 8.86, p < .01, ηp2 = .18; probe type, F(1, 40) = 11.22, p < .01, ηp2 = .22;
and age group, F(1, 40) = 30.86, p < .001, ηp2 = .44, as well as a significant interaction between
recency and probe type, F(1, 40) = 26.46, p < .001, ηp2 = .40. Negative and nonrecent trials were
answered more correctly than positive or recent trials. However, the recency effect appeared only in
the negative trials, therefore, the significant interaction. The remaining two-way interactions between
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recency and age group, probe type, and age group, as well as the three-way interaction failed to reach
significance (highest F = 2.77, lowest p = .104).
N-back. A repeated-measurements ANOVA with age group (children, younger adults, older adults) as
the between-subjects factor and trial condition (targets, lures, nones) as the within-subject factor
revealed significant main effects of trial condition, F(1.31, 116.64) = 80.41, p < .001, ηp2 = .48, and of
age group, F(2, 89) = 41.45, p < .001, ηp2 = .48, and a significant interaction between both, F(2.62,
116.64) = 19.51, p < .001, ηp2 = .31. Overall, younger adults responded more correctly than older
adults and children (planned pairwise contrasts, p < .001). Accuracy scores were highest in the nones,
then in the lures, and worst in the targets (two-tailed pairwise comparisons, significant differences
between all trial conditions, p < .05). While children had most difficulties with the target trials, for the
older adults, the interference condition was the most difficult (see Figure S2).
A subsequent ANOVA within both children groups revealed a main effect of trial condition, F(1.31,
52.39) = 71.04, p < .001, ηp2 = .64; a main effect of age group, F(1, 40) = 17.32, p < .001, ηp2 = .30;
and a significant interaction between both, F(1.31, 52.39) = 4.03, p < .05, ηp2 = .09. There were
significant differences between all trial conditions (p < .001). As in the overall sample, accuracy
scores were highest in the nones, then in the lures, and lowest in the targets. The interaction showed
that although the performance in the negative trials was almost similar for both groups, younger
children performed worse in the target condition than older children.
Reaction Times
Recent-probes task. A repeated-measurements ANOVA with age group (children, younger adults,
older adults) as the between-subjects factor and recency (recent vs. non-recent) and probe type
(positive vs. negative) as the within-subject factors showed that all main effects were significant at p <
.001—recency: F(1, 89) = 28.82, ηp2 = .25; probe type: F(1, 89) = 34.80, ηp2 = .28; age group: F(2, 89)
= 37.57, ηp2 = .46. Nonrecent trials were answered faster than recent trials, and positive trials were
answered faster than negative trials. A U-shaped pattern concerning age appeared, with the young
adults performing faster than older adults and children (both p < .001). The interaction between
recency and probe type was significant, F(1, 89) = 16.49, p < .001, ηp2 = .16. In the negative trials,
recent trials were answered slower than nonrecent trials while in the positives, RTs for both
conditions were nearly equal. The interaction between age group and recency reached marginal
significance, F(2, 89) = 3.02, p = .054, ηp2 = .06 (greater recency effect in older adults than in the
other groups) and reached significance in the interaction between probe type and age group, F(2, 89)
= 5.51, p < .01, ηp2 = .11 (larger effect in the older adults than in the other groups). As in the accuracy
data, the three-way interaction failed to reach significance, F(2, 89) = 0.35, p = .708, ηp2 = .01.
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The subsequent ANOVA within the children sample revealed a marginally significant main effect of
recency, F(1, 40) = 4.02, p = .052, ηp2 = .09); a significant main effect of probe type, F(1, 40) = 4.99,
p < .05, ηp2 = .11; and a significant main effect of age group, F(1, 40) = 19.26, p < .001, ηp2 = .33.
Nonrecent or positive trials were answered faster than recent or negative trials, and older children
were faster than younger children. There was also a marginally significant interaction between
recency and probe type, F(1, 40) = 3.82, p = .058, ηp2 = .09. The other interactions failed to reach
significance (highest F = 1.43, lowest p = .239).
N-back. A repeated-measurements ANOVA with age group (children, younger adults, older adults) as
the between-subjects factor and trial condition (targets, lures, nones) as the within-subject factor
revealed main effects of trial condition, F(1.53, 136.10) = 8.76, p < .001, ηp2 = .09, and of age group,
F(2, 89) = 4.58, p < .05, ηp2 = .09. The interaction between trial condition and age group was also
significant, F(3.06, 136.10) = 3.60, p < .05, ηp2 = .08. Planned pairwise contrasts revealed that older
adults answered more slowly than younger adults (p < .01). There was a trend that adults were faster
than children (p = .080). Comparing the different conditions with two-tailed pairwise comparisons, it
was found that nones were answered faster than targets (p < .05) and lures (p < .001); however, the
RT of targets and lures did not differ (p = .203).
Subsequent analyses with the two children groups revealed a significant main effect of trial condition,
F(1.30, 52.17) = 5.57, p < .05, ηp2 = .12; a significant interaction between age group and trial
condition, F(1.30, 52.17) = 9.18, p < .01, ηp2 = .19; but no main effect of age group, F(1, 40) = 0.39, p
= .535, ηp2 = .01. Whereas there was only a small difference in the performance of the negative trials
between both groups, younger children took about 200 ms longer than older children to answer the
target trials in this task, which, like the low accuracy scores, may express difficulties with the working
memory condition (see Figure S2). In general, targets and lures were answered more slowly than
nones (both p <. 01); however, RTs in the targets and the lures did not differ significantly (p = .153).
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--- Figures S1 and S2 ---
Figure S1. Working memory performance (mean accuracies and latencies) in the recent-probes task in
all conditions for each age group. Error bars reflect standard errors of the mean. Pos = positive trials;
Neg = negative Trials; R = recent trials; NR = nonrecent trials.
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Figure S2. Working memory performance (mean accuracies and latencies) in the n-back task in all
conditions for each age group. Error bars reflect standard errors of the mean.