Spatial clustering and hierarchical coding in immediate serial recall

Four experiments are reported that demonstrate the benefits of clustering by spatial proximity in spatial serial recall and provide support for the notion that hierarchical coding underpins the retention of clustered sequences in spatial working memory. Sequences segregated by spatial clusters increased serial recall performance at different levels of sequence length in a variation of the Corsi test and produced a faster initial response time (RT), which indicates that they afforded data reducing processes. RT at cluster boundary increased in parallel with the number of items forming the clusters, suggesting that subroutines of different length were responsible for the ordering of items within clusters of different size. Evidence for hierarchical coding was also obtained in a serial recognition task, indicating this type of representation pertains to the retention of the sequences rather than exclusively to the organisation of the motor plan for the reproduction of the sequences.     

The irrelevant sound effect in short-term memory: Is there developmental change?

With two experiments, effects of irrelevant speech and classroom noise on serial recall of common nouns presented pictorially were investigated in children and adults. Experiment 1 used fixed list lengths for children (first graders) and adults. Experiment 2 used list lengths adjusted to participants' (second–third graders, adults) individual spans. In both experiments, children and adults were equally impaired by irrelevant speech. This contrasts with a related study (differences in methodology) by Elliott (2002), who reported severe increase in the detrimental impact of irrelevant speech with decreasing age. In both experiments, classroom noise had no effect in overall analyses. For Experiment 1, however, separate group analyses revealed impairment in children. Results suggest that effects of irrelevant sounds on serial recall stem from two separate mechanisms: Specific interference due to the sounds' automatic access to short-term memory, and/or attention capture. Only for the latter there is developmental change.     

Immediate recognition memory for wine

We describe a preliminary investigation concerning the short-term recognition memory function for gustatory stimuli (wines). In Experiment 1A, 24 non-expert wine drinkers completed a yes/no recognition task for 3-wine sequences. For the raw recognition scores, the serial position function comprised both primacy and recency. Recency did not, however, achieve significance for the d′ scores. In Experiment 1B, 24 participants completed the same yes/no recognition task for 3-visual matrix sequences. In contrast to Experiment 1A, the serial position function comprised recency and an absence of primacy. We argue that the presence of primacy for the wine sequences cannot be interpreted via a verbal labelling strategy, nor can it be interpreted via proactive interference from the first wine in the list on subsequent list items. The result suggests qualitative differences in the memory processing for gustatory and non-verbal visual stimuli.     

Modality independence of order coding in working memory: Evidence from cross-modal order interference at recall

Working memory researchers do not agree on whether order in serial recall is encoded by dedicated modality-specific systems or by a more general modality-independent system. Although previous research supports the existence of autonomous modality-specific systems, it has been shown that serial recognition memory is prone to cross-modal order interference by concurrent tasks. The present study used a serial recall task, which was performed in a single-task condition and in a dual-task condition with an embedded memory task in the retention interval. The modality of the serial task was either verbal or visuospatial, and the embedded tasks were in the other modality and required either serial or item recall. Care was taken to avoid modality overlaps during presentation and recall. In Experiment 1, visuospatial but not verbal serial recall was more impaired when the embedded task was an order than when it was an item task. Using a more difficult verbal serial recall task, verbal serial recall was also more impaired by another order recall task in Experiment 2. These findings are consistent with the hypothesis of modality-independent order coding. The implications for views on short-term recall and the multicomponent view of working memory are discussed.     

Within-word serial order control: Adjacent mora exchange and serial position effects in repeated single-word production

An essential function of language processing is serial order control. Computational models of serial ordering and empirical data suggest that plan representations for ordered output of sound are governed by principles related to similarity. Among these principles, the temporal distance and edge principles at a within-word level have not been empirically demonstrated separately from other principles. Specifically, the temporal distance principle assumes that phonemes that are in the same word and thus temporally close are represented similarly. This principle would manifest as phoneme movement errors within the same word. However, such errors are rarely observed in English, likely reflecting stronger effects of syllabic constraints (i.e., phonemes in different positions within the syllable are distinctly represented). The edge principle assumes that the edges of a sequence are represented distinctly from other elements/positions. This principle has been repeatedly observed as a serial position effect in the context of phonological short-term memory. However, it has not been demonstrated in single-word production. This study provides direct evidence for the two abovementioned principles by using a speech-error induction technique to show the exchange of adjacent morae and serial position effects in Japanese four-mora words. Participants repeatedly produced a target word or nonword, immediately after hearing an aurally presented distractor word. The phonologically similar distractor words, which were created by exchanging adjacent morae in the target, induced adjacent-mora-exchange errors, demonstrating the within-word temporal distance principle. There was also a serial position effect in error rates, such that errors were mostly induced at the middle positions within a word. The results provide empirical evidence for the temporal distance and edge principles in within-word serial order control.     

Implicit visual learning: How the task set modulates learning by determining the stimulus–response binding

Implicit learning is one of the most fundamental learning mechanisms that enables humans to adapt to regularities inherent in the environment. Despite its high flexibility, it depends on constraints, such as selective attention. Here, we focused on the stimulus-to-response binding which defines the dimensions of the stimuli and the responses participants attend to. In a serial reaction time task with a visual sequence, we investigated whether this stimulus–response binding influences the amount of sequence learning. The results of Experiments 1 and 2 showed that visual sequence learning is reduced when participants do not attend to the relevant response dimension. Furthermore, the findings of Experiment 3 suggest that attention to the relevant response dimension increased the development of explicit knowledge without affecting implicit knowledge. This latter finding is difficult to reconcile with the assumption that explicit learning results from the gradual strengthening of sequence representations.     

How do humans group non-rigid objects in multiple object tracking?: Evidence from grouping by self-rotation

Previous studies on perceptual grouping found that people can use spatiotemporal and featural information to group spatially separated rigid objects into a unit while tracking moving objects. However, few studies have tested the role of objects’ self-motion information in perceptual grouping, although it is of great significance to the motion perception in the three-dimensional space. In natural environments, objects always move in translation and rotation at the same time. The self-rotation of the objects seriously destroys objects’ rigidity and topology, creates conflicting movement signals and results in crowding effects. Thus, this study sought to examine the specific role played by self-rotation information on grouping spatially separated non-rigid objects through a modified multiple object tracking (MOT) paradigm with self-rotating objects. Experiment 1 found that people could use self-rotation information to group spatially separated non-rigid objects, even though this information was deleterious for attentive tracking and irrelevant to the task requirements, and people seemed to use it strategically rather than automatically. Experiment 2 provided stronger evidence that this grouping advantage did come from the self-rotation per se rather than surface-level cues arising from self-rotation (e.g. similar 2D motion signals and common shapes). Experiment 3 changed the stimuli to more natural 3D cubes to strengthen the impression of self-rotation and again found that self-rotation improved grouping. Finally, Experiment 4 demonstrated that grouping by self-rotation and grouping by changing shape were statistically comparable but additive, suggesting that they were two different sources of the object information. Thus, grouping by self-rotation mainly benefited from the perceptual differences in motion flow fields rather than in deformation. Overall, this study is the first attempt to identify self-motion as a new feature that people can use to group objects in dynamic scenes and shed light on debates about what entities/units we group and what kinds of information about a target we process while tracking objects.     

Serial position effects in 2-alternative forced choice recognition: Functional equivalence across visual and auditory modalities

Two experiments examined Ward, Avons, and Melling's (2005) proposition that the serial position function is task, rather than modality, dependent. Specifically, they proposed that for backward testing the 2-alternative forced-choice (2AFC) recognition paradigm is characterised by single-item recency irrespective of the modality of the stimulus presentation. In Experiment 1 the same nonword sequences, presented both visually or auditorily, produced qualitatively equivalent serial position functions with 2AFC testing. Forward testing produced a flat serial position function, while backward testing produced two-item recency in the absence of primacy. In order to rule out the possibility that the serial position functions for visual stimuli were the product of sub-vocal rehearsal, Experiment 2 employed articulatory suppression during the presentation phase. Serial position function equivalence was again observed together with a modest impairment in overall recognition rates. Taken together, these data are consistent with the Ward et al. proposition and further support the existence of a visual memory that can facilitate storage of visual-verbal material (e.g. Logie, Della Sella, Wynn, & Baddeley, 2000). However, the observation of two-item recency contradicts the original duplex account of single-item recency traditionally observed for backwards recognition testing of visual stimuli (Phillips & Christie, 1977).     

Serial and subjective clustering on a verbal learning test (VLT) in children aged 5–15: The nature of subjective clustering

This study investigated which strategies children aged 5–15 years (N?=?408) employ while performing a multitrial free recall test of semantically unrelated words. Serial clustering (i.e., a relatively passive strategy) is an index of the sequential consistency of recall order. Subjective clustering (i.e., a more active strategy) is based on similar word groupings in successive trials. Previously, Meijs et al. (2009 Meijs, C. J. C., Hurks, P. P. M., Kalff, A. C., Slaats-Willemse, D. I. E., Rozendaal, N. and Jolles, J. 2009. Differential development of learning strategies on a Pictorial Verbal Learning Test (PVLT) in primary school children. Child Neuropsychology, 15: 247–261. [Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]) found that the level of (serial and subjective) clustering increases with age. At all ages, the level of serial clustering correlates positively with the ability to recall information on VLT trials. However, subjective clustering is more predictive of VLT performance than serial clustering after ≥ 3 trials, but only in children aged 8+. Knowledge on how children organize words (based on, for example, sound or meaning) and how this relates to developmental stage is still lacking. This study revealed that the level of subjective clustering is primarily determined by the position of words in a VLT list. More specifically, primacy (i.e., recall of words 1–3 of the VLT list — whether recalled in the same order or reversed) and recency (i.e., recall of words 14–15) effects primarily determine level subjective organization over successive trials. Thus, older children still organize words based on the serial position of the VLT list and are much less likely to organize them based on any other feature of the words, for example, sound or meaning. This indicates that the most important information to be learned needs to be presented first or last, even in older children and even with repeated presentations.     

Whom to help? Immediacy bias in judgments and decisions about humanitarian aid

People exhibit an immediacy bias when making judgments and decisions about humanitarian aid, perceiving as more deserving and donating disproportionately to humanitarian crises that happen to arouse immediate emotion. The immediacy bias produced different serial position effects, contingent on decision timing (Experiment 1). When making allocation decisions directly after viewing to four emotionally evocative films about four different humanitarian crises, participants donated disproportionately more to the final, immediate crisis, in contrast, when making donation decisions sequentially, after viewing each of the four crises, participants donated disproportionately to the immediate crisis. The immediacy bias was associated with “scope neglect,” causing people to take action against relatively less deadly crises (Experiments 2 and 3). The immediacy bias emerged even when participants were warned about emotional manipulation (Experiment 3). The immediacy bias diminished over time, as immediate emotions presumably subsided (Experiment 2). Implications for charitable giving, serial position effects, and the influence of emotion on choice are discussed.