Are working memory training effects paradigm-specific?
TL;DR: Transfer is constrained by working memory paradigm and the nature of individual processes executed within complex span tasks, however, within-paradigm transfer can occur when the change is limited to stimulus category, at least for n-back.
Abstract: A randomized controlled trial compared complex span and n-back training regimes to investigate the generality of training benefits across materials and paradigms. The memory items and training intensities were equated across programs, providing the first like-with-like comparison of transfer in these two widely-used training paradigms. The stimuli in transfer tests of verbal and visuo-spatial n-back and complex span differed from the trained tasks, but were matched across the untrained paradigms. Pre-to-post changes were observed for untrained n-back tasks following n-back training. Following complex span training there was equivocal evidence for improvements on a verbal complex span task, but no evidence for changes on an untrained visuo-spatial complex span activity. Relative to a no intervention group, the evidence supported no change on an untrained verbal complex span task following either n-back or complex span training. Equivocal evidence was found for improvements on visuo-spatial complex span and verbal and visuo-spatial n-back tasks following both training regimes. Evidence for selective transfer (comparing the two active training groups) was only found for an untrained visuo-spatial n-back task following n-back training. There was no evidence for cross-paradigm transfer. Thus transfer is constrained by working memory paradigm and the nature of individual processes executed within complex span tasks. However, within-paradigm transfer can occur when the change is limited to stimulus category, at least for n-back.
Summary (3 min read)
- They concluded that “transfer can occur if the criterion and transfer tasks engage specific overlapping processing components and brain regions” (p. 1510).
- If only the higher-level task structure of alternating stimulus presentation and distractor processing episodes needs to be preserved, there should be transfer to other complex span tasks with different stimuli and distractor processing activities.
- Data were excluded for eight participants who failed to complete all training sessions and four participants who did not attend for the Time 2 assessment.
- The training program failed for one participant.
- Further participants were recruited to replace those with incomplete data.
- The final sample included 48 native-English speaking adults aged between 18 and 35 years (12 males, mean age 28 years and 9 months).
- Participants were recruited through the MRC Cognition and Brain Sciences Unit research participation system and provided written informed consent prior to participation.
- Participants in the complex span training group completed 32 trials per training session, 16 trials each on the verbal and visuospatial tasks.
- The presentation rate of the storage items and overall length of each processing episode (6000 ms) was identical to the transfer tasks.
- Average RTs for correct items were calculated and 50% was added to calculate the rate of presentation during training.
- Participants were required to judge whether each stimulus was a real word by clicking on “word” or “non-word” buttons.
- Participants could respond as soon as each pattern was presented by clicking onscreen buttons labeled “symmetrical” and “asymmetrical.”.
- Participants completed 10 blocks of verbal n-back and 10 blocks of visuo-spatial n-back in each training session, totalling 20 blocks per session.
- The n-back training tasks differed from the transfer tasks only in the stimuli – all other features including the presentation rate of the stimuli were the same as in the transfer tasks.
- Training started with a block of trials at 1-back and adapted up and down to match participants’ current performance throughout each training session.
- If there were fewer than three errors (sum of misses and false alarms) in block, the level of n-back increased by one in the next block.
- In all other cases the level of n remained the same.
- Bayesian ANOVAs were conducted to analyze on-task training gains across the four training tasks with session (2–20) and training task (four training tasks) entered as factors.
- In the first, dummy variables one (D1) and two (D2) were entered to compare the effects of n-back training to complex span training (D1 result) and to compare complex span training to no intervention (D2 result).
- Three questions were addressed in the analyses.
- This is the most stringent comparison that allows us to examine the paradigmspecificity of transfer.
- Bayesian methods were conducted in JASP (Love et al., 2015) with default prior scales.
- All participants completed four tasks during a Time 1 assessment at the MRC Cognition and Brain Sciences Unit lasting approximately 1 h.
- Trainees completed the subsequent 18 online training sessions remotely (e.g., at home) before returning to the MRC Cognition and Brain Sciences Unit to complete their final training session and a Time 2 assessment that was identical to the Time 1 assessment.
- Participants were paid £6 per hour for their time plus a contribution toward travel costs.
- Data failed to upload for the final two sessions for three participants on the n-back training tasks.
- Analyses testing for the effect of training task order were run including sessions where there was complete data for all participants (Sessions 2–18 for both tasks).
Training Task Progress
- To provide a comparable measure of changes across time across each training task, a standard gain score was calculated by dividing the difference between the average difficulty level attained on each session and the first session by the SD for the first session (Harrison et al., 2013).
- These scores relative to the first session of training are shown in Figure 2.
- Improvements of at least 1SD from baseline were observed on all training tasks.
- Note that Session 1 was not included as participants were reaching baseline during this session.
- Bayesian t-tests compared pre- to post- scores for each of the four outcome measures for each training group (see Table 3).
- There was equivocal evidence for transfer to verbal complex span, verbal n-back and visuo-spatial n-back following complex span training, with evidence favoring a null effect for transfer to visuo-spatial complex span following complex span training (BF = 0.325).
- To investigate whether group differences in post-test scores on this task were associated with differences in baseline scores both centered baseline scores and centered baseline score × group product terms were also entered into the regression models.
- The outcomes of the regression analyses for each transfer task comparing each active training group to the no intervention group (testing for re-test effects) are reported in Table 4.
- Evidence for differences in transfer on the verbal n-back transfer task between the n-back and complex span training groups was equivocal (BF = 0.542), as for equivocal differences between the n-back and no intervention groups on this transfer measure.
- This training study compared transfer patterns from two working memory training paradigms (n-back and complex span) matched for memory items (letters and spatial locations) and training intensity to outcome measures that were also matched for memory items (digits and objects).
- Note, though, that the present findings do not distinguish between these two alternative accounts, which claim that transfer is limited either by process (Dahlin et al., 2008) and paradigm Gathercole et al. (2019).
- Relative to a no intervention group, there was no strong evidence for the benefits of n-back training for untrained n-back tasks.
- The strength of transfer from complex span training to other complex span tasks with different materials and distractor Frontiers in Psychology | www.frontiersin.org 7 May 2019 | Volume 10 | Article 1103 processing was more equivocal.
- Together these findings suggest that the application of cognitive routines developed during the course of training (Gathercole et al., 2019) may operate at a relatively general level that is not tied to processes specific to particular categories of memory items when these are the only features altered between training and transfer, as in the case of n-back.
- Participants were recruited through the MRC Cognition and Brain Sciences Unit research participation system and provided informed consent prior to participation.
- Ethical approval was obtained from the University of Cambridge’s Psychology Research Ethics Committee (PRE.2012.86).
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"Are working memory training effects..." refers methods in this paper
...The word stimuli were drawn at random from a pool of 187 items generated by searching the MRC Psycholinguistic database (Colheart, 1981) for single syllable words of 4-6 letters with Kucera-Francis written word frequency > 50 per million (Kučera & Francis, 1967)....
"Are working memory training effects..." refers methods in this paper
...…consistent with many previous studies in which less systematic designs have been used to map transfer (Bürki et al., 2014; Chooi & Thompson, 2012; Jaeggi et al., 2008; Jaeggi et al., 2010; Li et al., 2008; Lilienthal et al., 2013; Minear et al., 2016; Oelhafem, Nikolaidis, Padovani, Blaser,…...
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Relative to a no intervention group, the evidence supported no change on an untrained verbal complex span task following either n-back or complex span training. Evidence for selective transfer ( comparing the two active training groups ) was only found for an untrained visuo-spatial n-back task following n-back training.