Articulatory suppression and the irrelevant-speech effect in short-term memory: does the locus of suppression matter?

Irrelevant speech impairs serial recall of verbal but not spatial items in children and adults

Immediate serial recall of visually presented items is reliably impaired by task-irrelevant speech that the participants are instructed to ignore ("irrelevant speech effect," ISE). The ISE is stronger with changing speech tokens (words or syllables) when compared to repetitions of single tokens ("changing-state effect," CSE). These phenomena have been attributed to sound-induced diversions of attention away from the focal task (attention capture account), or to specific interference of obligatory, involuntary sound processing with either the integrity of phonological traces in a phonological short-term store (phonological loop account), or the efficiency of a domain-general rehearsal process employed for serial order retention (changing-state account). Aiming to further explore the role of attention, phonological coding, and serial order retention in the ISE, we analyzed the effects of steady-state and changing-state speech on serial order reconstruction of visually presented verbal and spatial items in children (n = 81) and adults (n = 80). In the verbal task, both age groups performed worse with changing-state speech (sequences of different syllables) when compared with steady-state speech (one syllable repeated) and silence. Children were more impaired than adults by both speech sounds. In the spatial task, no disruptive effect of irrelevant speech was found in either group. These results indicate that irrelevant speech evokes similarity-based interference, and thus pose difficulties for the attention-capture and the changing-state account of the ISE.

The Impact of Different Types of Auditory Warnings on Working Memory

Auditory warnings have been shown to interfere with verbal working memory. However, the impact of different types of auditory warnings on working memory tasks must be further researched. This study investigated how different kinds of auditory warnings interfered with verbal and spatial working memory. Experiment 1 tested the potential interference of auditory warnings with verbal working memory. Experiment 2 tested the potential interference of auditory warnings with spatial working memory. Both experiments used a 3 × 3 mixed design: auditory warning type (auditory icons, earcons, or spearcons) was between groups, and task condition (no-warning, identify-warning, or ignore-warning) was within groups. In Experiment 1, earcons and spearcons but not auditory icons worsened the performance on the verbal serial recall task in the identify-warning condition, compared with that in the no-warning or ignore-warning conditions. In Experiment 2, only identifying earcons worsened the performance on the location recall task compared with performance without auditory warnings or when auditory warnings were ignored. Results are discussed from the perspective of working memory resource interference, and their practical application in the selection and design of auditory warning signals is involved.

Does articulatory rehearsal help immediate serial recall?

Articulatory rehearsal is assumed to benefit verbal working memory. Yet, there is no experimental evidence supporting a causal link between rehearsal and serial-order memory, which is one of the hallmarks of working memory functioning. Across four experiments, we tested the hypothesis that rehearsal improves working memory by asking participants to rehearse overtly and by instructing different rehearsal schedules. In Experiments 1a, 1b, and 2, we compared an instructed cumulative-rehearsal condition against a free-rehearsal condition. The instruction increased the prevalence of cumulative rehearsal, but recall performance remained unchanged or decreased compared to the free-rehearsal baseline. Experiment 2 also tested the impact of a fixed rehearsal instruction; this condition yielded substantial performance costs compared to the baseline. Experiment 3 tested whether rehearsals (according to an experimenter-controlled protocol) are beneficial compared to a matched articulatory suppression condition that blocked rehearsals of the memoranda. Again, rehearsing the memoranda yielded no benefit compared to articulatory suppression. In sum, our results are incompatible with the notion that rehearsal is beneficial to working memory.

Interfering with free recall of words: Detrimental effects of phonological competition

We examined the effect of different distracting tasks, performed concurrently during memory retrieval, on recall of a list of words. By manipulating the type of material and processing (semantic, orthographic, and phonological) required in the distracting task, and comparing the magnitude of memory interference produced, we aimed to infer the kind of representation upon which retrieval of words depends. In Experiment 1, identifying odd digits concurrently during free recall disrupted memory, relative to a full attention condition, when the numbers were presented orthographically (e.g. nineteen), but not numerically (e.g. 19). In Experiment 2, a distracting task that required phonological-based decisions to either word or picture material produced large, but equivalent effects on recall of words. In Experiment 3, phonological-based decisions to pictures in a distracting task disrupted recall more than when the same pictures required semantically-based size estimations. In Experiment 4, a distracting task that required syllable decisions to line drawings interfered significantly with recall, while an equally difficult semantically-based color-decision task about the same line drawings, did not. Together, these experiments demonstrate that the degree of memory interference experienced during recall of words depends primarily on whether the distracting task competes for phonological representations or processes, and less on competition for semantic or orthographic or material-specific representations or processes.

Hebbian learning for olfactory sequences

The present paper explores the generality of the Hebb repetition effect to the learning of olfactory sequences in order to assess commonality of memory functioning across sensory modalities. Participants completed a serial-order reconstruction task comprising sequences of four olfactory stimuli. Following presentation of each sequence, participants were re-presented with the odours and were required to reconstruct their order of presentation. Surreptitious re-presentation of the repeated sequence occurred on every third trial. This order reconstruction task produced a serial-position function comprising recency only for both the non-repeated and the repeated sequences. Importantly, serial-order reconstruction for the repeated odour sequence produced improved performance for that sequence compared to the non-repeated sequences. This observation of a Hebb repetition effect for olfactory sequences further supports the proposition that sequential learning can operate amodally.

Evaluating models of working memory through the effects of concurrent irrelevant information

Working memory is believed to play a central role in almost all domains of higher cognition, yet the specific mechanisms involved in working memory are still fiercely debated. We describe a neuroimaging experiment with functional magnetic resonance imaging (fMRI) and a companion behavioral experiment, and in both we seek to adjudicate between alternative theoretical models of working memory on the basis of the effects of interference from articulatory suppression, irrelevant speech, and irrelevant nonspeech. In Experiment 1 we examined fMRI signal changes induced by each type of irrelevant information while subjects performed a probed recall task. Within a principally frontal and left-lateralized network of brain regions, articulatory suppression caused an increase in activity during item presentation, whereas both irrelevant speech and nonspeech caused relative activity reductions during the subsequent delay interval. In Experiment 2, the specific timing of interference was manipulated in a delayed serial recall task. Articulatory suppression was found to be most consequential when it coincided with item presentation, whereas both irrelevant speech and irrelevant nonspeech effects were strongest when limited to the subsequent delay period. Taken together, these experiments provide convergent evidence for a dissociation of articulatory suppression from the 2 irrelevant sound conditions. Implications of these findings are considered for 4 prominent theories of working memory.

The processing of spatial information in short-term memory: insights from eye tracking the path length effect

Serial memory for spatial locations increases as the distance between successive stimuli locations decreases. This effect, known as the path length effect [Parmentier, F. B. R., Elford, G., & Maybery, M. T. (2005). Transitional information in spatial serial memory: Path characteristics affect recall performance. Journal of Experimental Psychology: Learning, Memory & Cognition, 31, 412-427], was investigated in a systematic manner using eye tracking and interference procedures to explore the mechanisms responsible for the processing of spatial information. In Experiment 1, eye movements were monitored during a spatial serial recall task--in which the participants have to remember the location of spatially and temporally separated dots on the screen. In the experimental conditions, eye movements were suppressed by requiring participants to incessantly move their eyes between irrelevant locations. Ocular suppression abolished the path length effect whether eye movements were prevented during item presentation or during a 7s retention interval. In Experiment 2, articulatory suppression was combined with a spatial serial recall task. Although articulatory suppression impaired performance, it did not alter the path length effect. Our results suggest that rehearsal plays a key role in serial memory for spatial information, though the effect of path length seems to involve other processes located at encoding, such as the time spent fixating each location and perceptual organization.