Benefitting from trial spacing without the cost of prolonged training: Frequency, not duration, of trials with absent stimuli enhances learning

The statistical relation between two events influences the perception of how well one event relates to the presence or absence of another. The simultaneous absence of both events, just like their mutual occurrence, is theoretically relevant for describing their contingency. However, humans tend to weight co-occurring information more heavily than co-absent information. We explored the relevance of co-absent events by varying the duration and frequency of trials without stimuli. In three experiments, we used a rapid trial streaming procedure, and found that the perceived association between events is enhanced with increased frequency of co-absent events. Duration of co-absent events did not play as strong role on judgments of association as did frequency. These findings suggest ways in which the benefits of trial spacing, which are effectively co-absence events, could be preserved without increasing total training time. Specifically, the present results suggest that the benefits of distributed practice can be obtained without increasing the length of the training session by shortening the intervals between events. We also discuss five potential accounts of how the co-absent experience is processed: contingency sensitivity, a memory testing effect, associative interference, reduced cognitive load, and consolidation.

More Efficient Shielding for Internal than External Attention? Evidence from Asymmetrical Switch Costs

At present, the process of switching attention between external stimuli and internal representations is not well understood. To address this, Verschooren and colleagues (2019) recently designed a novel paradigm where participants were cued to switch attention between external and internal information on a trial-by-trial basis. The authors observed an asymmetrical switch cost, which was larger when switching towards internal than external material, even though participants performed internal trials faster. In the current study, we sought to establish the cause of this asymmetry by adjudicating between predictions from three theoretical accounts: associative interference, priming, and memory retrieval. After replicating the original asymmetry (Experiment 1), we demonstrate that trial-by-trial carryover of attentional settings is not a necessary precondition (Experiment 2). The results from Experiment 3 indicate that the cost asymmetry can be best explained by an associative interference account, against a memory retrieval one. Together, these results therefor provide evidence in favor of an associative interference account and document that shielding attention for internal representations from external intrusions is more efficient than the other way around. This finding advances our understanding of a core aspect of cognitive flexibility and the relationship between external and internal attention. More research on this question and novel ones raised by it is necessary, however.