Hagit Magen

Intra- and cross-dimensional visual search for single-feature targets.

Cross-dimensional visual search for single-feature targets that differed from the distractors along two dimensions (color and orientation) was compared with intradimensional search for targets that differed from the distractors along a single dimension (either orientation or color). The design of the first three experiments differed from those of previous studies in that participants were required to respond differently to each of the targets. Experiments 1–3 were similar except that in Experiment 1, the distractors were homogeneous; in Experiment 2, two types of distractors were used in equal proportions; and in Experiment 3, two types of distractors were used but one of the distractors was a singleton. The findings, contrary to those of previous studies, revealed that cross-dimensional search is at least as efficient and for some targets even more efficient than intradimensional search. These results suggest that the details of stimulus-to-response mapping are essential in comparing intra- and cross-dimensional tasks. Experiment 4 used a priming design and did not support an explanation based on grouping processes. We outline an explanation for all the findings based on a recent cross-dimensional response selection model by Cohen and Shoup (1997).

Modularity beyond perception: Evidence from single task interference paradigms

We combine the Dimension-Action (DA) model with translational models to account for both the Stroop and the flanker effects. The basic assumption of the model is that there are distinct visual modules, each of which is endowed with both perception and response selection processes. We contrast this model with an alternative widespread view, the standard view, according to which the same response selection processes are shared by all tasks. The two views have different predictions concerning the flanker and Stroop tasks. Seven experiments test these predictions. The first five experiments show that there is a fundamental difference between the typical Stroop and flanker effects. Moreover, these experiments show that words denoting colors can affect print colors only when they are required for naming or when participants verbally mediate the print color task. Experiments 6 and 7 show that an analogous interaction between color and shape exists in the flanker task. These experiments as well as previous studies are consistent with the DA model and the modular view and pose serious difficulties for the standard view. Wider implications of a visual modular architecture are discussed as well.

Modularity beyond perception: Evidence from the PRP paradigm.

The Dimension Action (DA) model asserts that the visual system is modular, and that each task involves multiple-response mechanisms rather than a unitary-response selection mechanism. The model has been supported by evidence from single-task interference paradigms. We use the psychological refractory period paradigm and show that dual-task performance can also be explained by the DA model. In 6 experiments we contrasted predictions from the DA model with predictions from the Response Selection Bottleneck (RSB; Pashler, 1994) model asserting that dual-task limitations are due to a unitary-response selection mechanism. Task 1 in all experiments was a tone discrimination task. In Experiments 1 to 3, Task 2 was a variation of either the Stroop or the flanker tasks. Experiments 4 to 6 manipulated response selection directly. The results showed that response selection effects can be underadditive in some conditions and additive in others depending on the modular nature of the response effect. Together, the results support the existence of an underlying modular architecture as proposed by the DA model and pose serious difficulties for the RSB model.

Location specificity in response selection processes for visual stimuli

We used the psychological refractory period paradigm, in which participants respond to two successive tasks (T1 and T2). We created in T2 spatial and color Simon effects, known to be caused by response selection processes. Previous studies in which the spatial Simon effect was manipulated in T2 showed that this effect was underadditive, with stimulus onset asynchrony (SOA) between the targets for T1 and T2. In Experiment 1, we replicated these results with two versions of the spatial Simon effect. In contrast, in Experiment 2 we manipulated two versions of a color Simon effect, revealing an additive relation between the color Simon effect and SOA. These results suggest that the underadditivity obtained with the spatial Simon effect is due to its spatial nature, and that space may play a unique role in response selection processes.

The relations between executive functions, media multitasking and polychronicity

Abstract Excessive media multitasking has been associated in a series of laboratory studies, with deficits in executive functions. Given that the levels of laboratory and everyday functioning do not always correspond, it is unclear whether media multitasking is associated with limitations in everyday executive functions as well. The current study examined the relationships between media multitasking and ecological self-report measures of executive functions, attention and a measure of individual preference for multitasking. The results demonstrated that participants who reported more deficits with different aspects of everyday executive functions and attention were engaged more frequently in media multitasking. Media multitasking was correlated most strongly with limitations in self-monitoring, emotional control, planning, task monitoring and inattention. Additionally, individuals who reported more deficits in executive functions and attention also reported a higher preference for multitasking over single-tasking. Taken together, the present study demonstrates that frequent media multitasking is associated with deficits in many aspects of everyday goal-directed behavior. The results generalize previous findings to self-report ecological measures of executive functions, and associate media multitasking with impairments in additional yet unexplored aspects of executive functions.

Correlational cuing as a function of target complexity and target-flanker similarity.

It is generally assumed that the correlational cuing effect (CE) between targets and correlated flankers is due to learning association between the flankers and their correlated responses. The present study challenges this view. Experiment 1 shows that the CE for targets composed of color is eliminated as soon as the correlation is removed. Experiment 2 shows that the CE during training is not due to association of the flankers with responses. Experiment 3 shows that at least some of the CE during training with the correlation is due to repetition priming of the display. Experiment 4 replicates the results of Experiment 1 for orientation targets. In Experiments 5–7, more typical tasks with letter targets are examined, and it is demonstrated that preexperimental similarity between targets and correlated flankers is crucial. The CE for correlated but dissimilar target-flanker pairs, similar to that for color and orientation targets, is confined to on-line processes that occur during training. The CE is transferred, however, for correlated and similar target-flanker pairs. We propose that, at least for the simple stimulus to response mapping used in our study, the CE is not due to learning at all. Instead it is due to (1) on-line processes, such as repetition priming, that occur during training with the correlation and (2) a regular flanker effect (see, e.g., B. A. Eriksen & C. W. Eriksen, 1974) that occurs for similar target-flanker pairs.

Neural evidence for sequential selection of object features

Behavioral and neural evidence suggests that attention selects entire objects, amplifying all of their features regardless of task relevance. A new magnetoencephalography (MEG) study by Schoenfeld et al. elucidates the time course of this selection, showing that object features are activated sequentially, with attention spreading from task-relevant to task-irrelevant modules.

Working memory for self-initiated and provided spatial configurations

During a typical day, people temporarily memorise information provided to them. However, they memorise as often information they actively choose themselves. Although prevalent in everyday behaviour, this aspect of working memory (WM), we term self-initiated WM, has been largely unexplored. In this study, we used a modified spatial span task in which participants constructed the spatial sequences they maintained in memory. The results of three experiments demonstrated that participants planned and constructed structured spatial sequences by minimising the distances between successive locations and by selecting sequences with fewer path crossings. The sequences were initiated most often on the top left side. Memory accuracy was enhanced when participants memorised self-initiated spatial sequences, even when the self-initiated and provided sequences were matched for structure. When asked to construct spatial sequences for a hypothetical competitor in a memory contest, participants constructed complex sequences with longer paths and more path crossings, suggesting that these sequence parameters were under their control. The tendency to initiate the spatial sequences on the top left side remained. Overall, the results suggest that self-initiated WM can benefit from explicit metacognitive knowledge of the ideal structure of memory representations and also demonstrate that self-initiation benefits memory beyond structure.

The role of central attention in retrieval from visual short-term memory.

The role of central attention in visual short-term memory (VSTM) encoding and maintenance is well established, yet its role in retrieval has been largely unexplored. This study examined the involvement of central attention in retrieval from VSTM using a dual-task paradigm. Participants performed a color change-detection task. Set size varied between 1 and 3 items, and the memory sample was maintained for either a short or a long delay period. A secondary tone discrimination task was introduced at the end of the delay period, shortly before the appearance of a central probe, and occupied central attention while participants were searching within VSTM representations. Similarly to numerous previous studies, reaction time increased as a function of set size reflecting the occurrence of a capacity-limited memory search. When the color targets were maintained over a short delay, memory was searched for the most part without the involvement of central attention. However, with a longer delay period, the search relied entirely on the operation of central attention. Taken together, this study demonstrates that central attention is involved in retrieval from VSTM, but the extent of its involvement depends on the duration of the delay period. Future studies will determine whether the type of memory search (parallel or serial) carried out during retrieval depends on the nature of the attentional mechanism involved the task.

The accessory Simon effect within and across visual dimensions

The Dimension-Action model maintains that response selection in the visual system is modular, such that response selection based on a target’s feature occurs within modules. This study suggests that response selection processes based on a target’s spatial location occur within modules as well, where spatial locations are coded along with the feature information. From this perspective, the typical Simon effect, in which interference occurs between a target’s feature and its spatial location, occurs within modules. This study explored whether the unique characteristic of the spatial Simon, namely, its reduction with increased reaction time is typical of spatial intra-dimension but not of spatial cross-dimension Simon effects, using the accessory Simon task. Experiment 1 demonstrated that intra-dimension Simon effects were reduced with increased reaction time, a reduction that was modulated by the task relevance of the distractor. In contrast, cross-dimension accessory Simon effects were positive and increased with reaction time. Experiment 2 demonstrated that intra-dimension Simon effects were not reduced when space was conveyed symbolically by arrows. Overall, the study suggests that interference in the accessory Simon task is influenced not only by the nature of the irrelevant spatial information but also by the modular locus of the targets and distractors.