Memory reloaded: Memory load effects in the attentional blink

When two targets are presented in rapid succession, identification of the first is nearly perfect, while identification of the second is impaired when it follows the first by less than about 700 ms. According to bottleneck models, this attentional blink (AB) occurs because the second target is unable to gain access to capacity-limited working memory processes already occupied by the first target. Evidence for this hypothesis, however, has been mixed, with recent reports suggesting that increasing working memory load does not affect the AB. The present paper explores possible reasons for failures to find a link between memory load and the AB and shows that a reliable effect of load can be obtained when the item directly after T1 (Target 1) is omitted. This finding provides initial evidence that working memory load can influence the AB and additional evidence for a link between T1 processing time and the AB predicted by bottleneck models.     

The contribution of phonological short-term memory to artificial grammar learning

Three experiments investigated the contribution of phonological short-term memory (STM) to grammar learning by manipulating rehearsal during study of an auditory artificial grammar made up from a vocabulary of spoken Mandarin syllables. Experiment 1 showed that concurrent, irrelevant articulation impaired grammar learning compared with a nonverbal control task. Experiment 2 replicated and extended this finding, showing that repeating the grammatical strings at study improved grammar learning compared with suppressing rehearsal or remaining silent during learning. Experiment 3 found no effects of rehearsal on grammar learning once participants had learned the component syllables. The findings suggest that phonological STM aids artificial grammar learning via effects on vocabulary learning.     

The effects of acute exercise on temporal generalization

Sixteen healthy college students performed a multiple-trial referenced temporal generalization task and an episodic temporal generalization task before and during moderate-intensity aerobic exercise. The same tasks were performed in a resting control condition. Working memory tasks were also administered before, during, and after exercise to determine whether exercise affected working memory processes. Temporal generalization gradients demonstrated leftward shifts during exercise when compared to rest, indicating that the subject perceived intervals to elapse more slowly. This finding is consistent with an increased pacemaker speed. Subjective lengthening of stimuli as the task progressed did not occur during exercise or rest. No significant differences were observed on the episodic timing task, nor were any differences found on the working memory tasks. These findings provide support for the notion that exercise influences the internal clock in a manner similar to other arousal-inducing manipulations.     

Whichever way you choose to categorize,working memory helps you learn

There has been growing interest in the relationship between the capacity of a person's working memory and their ability to learn to categorize stimuli. While there is evidence that working memory capacity (WMC) is related to the speed of category learning, it is unknown whether WMC predicts which strategies people use when there are multiple possible solutions to a categorization problem. To explore the relationship between WMC, category learning, and categorization strategy use, 173 participants completed two categorization tasks and a battery of WMC tasks. WMC predicted the speed of category learning, but it did not predict which strategies participants chose to perform categorization. Thus, WMC does not predict which categorization strategies people use but it predicts how well they will use the strategy they select.     

Working memory capacity predicts conflict-task performance

The relationship between the ability to maintain task goals and working memory capacity (WMC) is firmly established, but evidence for WMC-related differences in conflict processing is mixed. We investigated whether WMC (measured using two complex-span tasks) mediates differences in adjustments of cognitive control in response to conflict. Participants performed a Simon task in which congruent and incongruent trials were equiprobable, but in which the proportion of congruency repetitions (congruent trials followed by congruent trials or incongruent trials followed by incongruent trials) and thus the need for trial-by-trial adjustments in cognitive control varied by block. The overall Simon effect did not depend on WMC capacity. However, for the low-WMC participants the Simon effect decreased as the proportion of congruency repetitions decreased, whereas for the high- and average-WMC participants it was relatively constant across conditions. Distribution analysis of the Simon effect showed more evidence for the inhibition of stimulus location in the low- than in the high-WMC participants, especially when the proportion of congruency repetitions was low. We hypothesize that low-WMC individuals exhibit more interference from task-irrelevant information due to weaker preparatory control prior to stimulus presentation and, thus, stronger reliance on reactive recruitment of cognitive control.     

Precision of working memory for speech sounds

Memory for speech sounds is a key component of models of verbal working memory (WM). But how good is verbal WM? Most investigations assess this using binary report measures to derive a fixed number of items that can be stored. However, recent findings in visual WM have challenged such “quantized” views by employing measures of recall precision with an analogue response scale. WM for speech sounds might rely on both continuous and categorical storage mechanisms. Using a novel speech matching paradigm, we measured WM recall precision for phonemes. Vowel qualities were sampled from a formant space continuum. A probe vowel had to be adjusted to match the vowel quality of a target on a continuous, analogue response scale. Crucially, this provided an index of the variability of a memory representation around its true value and thus allowed us to estimate how memories were distorted from the original sounds. Memory load affected the quality of speech sound recall in two ways. First, there was a gradual decline in recall precision with increasing number of items, consistent with the view that WM representations of speech sounds become noisier with an increase in the number of items held in memory, just as for vision. Based on multidimensional scaling (MDS), the level of noise appeared to be reflected in distortions of the formant space. Second, as memory load increased, there was evidence of greater clustering of participants' responses around particular vowels. A mixture model captured both continuous and categorical responses, demonstrating a shift from continuous to categorical memory with increasing WM load. This suggests that direct acoustic storage can be used for single items, but when more items must be stored, categorical representations must be used.     

Instruction and load effects on high-skill and low-skill individuals: A study in the domain of mental arithmetic

What happens when people are asked to respond as quickly or as accurately as possible? This study tested the effects of speed/accuracy instructions and working-memory load on people's strategy efficiency and strategy selection. Adult participants solved simple addition problems (Experiment 1) and simple multiplication problems (Experiment 2) under load and no-load conditions and provided trial-by-trial strategy reports. High-skill participants were more efficient than low-skill participants, but the underlying causes of these skill-related effects differed across experiments. In the addition experiment, high-skill participants responded adaptively to the changing situations by changing their strategy choices, which resulted in smaller effects on their actual performance. Low-skill participants in contrast, did not change their strategy choices as adaptively, which resulted in less efficient performance—and especially so under load conditions. In the multiplication experiment, high-skill and low-skill participants differed in strategy efficiencies rather than in strategy choices. In the discussion, the results are further interpreted and future adaptations for the adaptive strategy choice model (ASCM; Siegler & Jenkins, 1989) are suggested.     

A dissociation between the sense of familiarity and access to semantic information concerning familiar people

In the current study we examined the relationship between working memory capacity, inhibition/susceptibility to interference and fluid intelligence, measured by the Raven's Progressive Matrices (PM38), comparing groups of young (aged 18–35), young-old (aged 65–74), and old-old (aged 75–86) participants. Groups were administered two working memory tasks tapping into different mechanisms involved in working memory. The ability to control for irrelevant information was measured both considering memory errors (intrusion errors) in a working memory task and an index of susceptibility to interference obtained with a variant of the Brown-Peterson task. Regression analyses showed that the classical working memory measure was the most potent predictors of the Raven's score. Susceptibility to interference and intrusions errors contributed, but to a lower extent, to the Raven explained variance. These results confirm that working memory shares cognitive aspects with the fluid intelligence measure considered, whereas the role of inhibition to Raven scores is still in need of better evidence.     

Executive control is shared between sentence processing and digit maintenance: Evidence from a strictly timed dual-task paradigm

We investigated whether the comprehension of syntactically difficult sentences taxes the executive control component of working memory more than the comprehension of their easier counterparts. To that end, we tested the effect of sharing executive control between sentence comprehension and the maintenance of a digit load in two dual-task experiments with strictly controlled timing (Barrouillet, Bernardin, & Camos, 2004). Recall was worse after participants had processed one (Experiment 2) or two (Experiment 1) difficult sentences than after they had processed one or two easy sentences, respectively. This finding suggests that sentence processing and the maintenance of a digit load share executive control. Processing syntactically difficult sentences seems to occupy executive control for a longer time than processing their easy counterparts, thereby blocking refreshments of the memory traces of the digits so that these traces decay more and recall is worse. There was no effect of the size of the digit load on sentence-processing performance (Experiment 2), suggesting that sentence processing completely occupied executive control until processing was complete.