The locus of the emotional Stroop effect: a study with the PRP paradigm

Semantic Stroop interference is modulated by the availability of executive resources: Insights from delta-plot analyses and cognitive load manipulation

We investigated whether, during visual word recognition, semantic processing is modulated by attentional control mechanisms directed at matching semantic information with task-relevant goals. In previous research, we analyzed the semantic Stroop interference as a function of response latency (delta-plot analyses) and found that this phenomenon mainly occurs in the slowest responses. Here, we investigated whether this pattern is due to reduced ability to proactively maintain the task goal in these slowest trials. In two pairs of experiments, participants completed two semantic Stroop tasks: a classic semantic Stroop task (Experiment 1A and 2A) and a semantic Stroop task combined with an n-back task (Experiment 1B and 2B). The two pairs of experiments only differed in the trial pace, which was slightly faster in Experiments 2A and 2B than in Experiments 1A and 1B. By taxing the executive control system, the n-back task was expected to hinder proactive control. Delta-plot analyses of the semantic Stroop task replicated the enhanced effect in the slowest responses, but only under sufficient time pressure. Combining the semantic Stroop task with the n-back task produced a change in the distributional profile of semantic Stroop interference, which we ascribe to a general difficulty in the use of proactive control. Our findings suggest that semantic Stroop interference is, to some extent, dependent on the available executive resources, while also being sensitive to subtle variations in task conditions.

Modulation of attentional bias by hypnotic suggestion: experimental evidence from an emotional Stroop task

Hypnosis is considered a unique tool capable of modulating cognitive processes. The extent to which hypnotic suggestions intervenes is still under debate. This study was designed to provide a new insight into this issue, by focusing on an unintentional emotional process: attentional bias. In Experiment 1, highly suggestible participants performed three sessions of an emotional Stroop task where hypnotic suggestions aiming to increase and decrease emotional reactivity towards emotional stimuli were administered within an intra-individual design. Compared to a baseline condition (without hypnotic suggestion), a significant increase in attentional bias was found when a hypnotic suggestion to increase emotional reactivity was administered. In contrast, the bias was eliminated when a suggestion to decrease emotional reactivity was administered. Experiment 2 investigated the effect of session repetition on attentional bias across three successive experimental sessions without hypnosis, and showed that the emotional Stroop effect did not vary across sessions. Hence, session repetition could not account for part of the modulation of attentional bias in Experiment 1. Taken together, the results suggest that specific hypnotic suggestions can influence elicitation of unintentional emotional processing. The implications are discussed regarding the locus of intervention of hypnotic suggestion in cognitive and emotional processes.

Response modalities and the cognitive architecture underlying action control: Intra-modal trumps cross-modal action coordination

Performing two actions at the same time usually hampers performance. Previous studies have demonstrated a strong impact of the particular effector systems on performance in multiple action control situations. However, an open question is whether performance is generally better or worse in situations in which two actions within the same effector system are coordinated (intra-modal actions: e.g., two pedal or two manual actions) compared to situations requiring two different effector systems (cross-modal actions: e.g., a manual combined with a vocal action). Performance differences can be predicated, among others, in the light of encapsulation accounts. Encapsulation of modules on the output side of processing would suggest that actions in two different modules can be triggered simultaneously without significant interference between the actions. Thus, cross-modal actions should lead to better performance compared to intra-modal actions. We investigated this issue in two basic experiments, in which participants responded to a single stimulus (thereby maximizing control over input and central processing stages) with one or two either intra-modal or cross-modal responses (manual-manual vs. manual-oculomotor/manual-vocal in Experiment 1/2, respectively). The results represent clear evidence for a performance advantage of intra-modal over cross-modal action control across both effector system combinations and independent of the particular spatial compatibility relation between responses. The results suggest performance benefits by taking advantage of integrated, holistic representations of intra-modal action compounds.

Dual task interference on early perceptual processing

When two tasks, Task 1 and Task 2, are conducted in close temporal proximity and a separate speeded response is required for each target (T1 and T2), T2 report performance decreases as a function of its temporal proximity to T1. This so-called psychological refractory period (PRP) effect on T2 processing is largely assumed to reflect interference from T1 response selection on T2 response selection. However, interference on early perceptual processing of T2 has been observed in a modified paradigm, which required changes in visual-spatial attention, sensory modality, task modality, and response modality across targets. The goal of the present study was to investigate the possibility of early perceptual interference by systematically and iteratively removing each of these possible non perceptual confounds, in a series of four experiments. To assess T2 visual memory consolidation success, T2 was presented for a varying duration and immediately masked. T2 report accuracy, which was taken as a measure of perceptual-encoding or consolidation-success, decreased across all experimental control conditions as T1-T2 onset proximity increased. We argue that our results, in light of previous studies, show that central processing of a first target, responsible for the classical PRP effect, also interferes with early perceptual processing of a second target. We end with a discussion of broader implications for psychological refractory period and attentional blink effects.

Two sources of task prioritization: The interplay of effector-based and task order-based capacity allocation in the PRP paradigm

When processing of two tasks overlaps, performance is known to suffer. In the well-established psychological refractory period (PRP) paradigm, tasks are triggered by two stimuli with a short temporal delay (stimulus onset asynchrony; SOA), thereby allowing control of the degree of task overlap. A decrease of the SOA reliably yields longer RTs of the task associated with the second stimulus (Task 2) while performance in the other task (Task 1) remains largely unaffected. This Task 2-specific SOA effect is usually interpreted in terms of central capacity limitations. Particularly, it has been assumed that response selection in Task 2 is delayed due to the allocation of less capacity until this process has been completed in Task 1. Recently, another important factor determining task prioritization has been proposed—namely, the particular effector systems associated with tasks. Here, we study both sources of task prioritization simultaneously by systematically combining three different effector systems (pairwise combinations of oculomotor, vocal, and manual responses) in the PRP paradigm. Specifically, we asked whether task order-based task prioritization (SOA effect) is modulated as a function of Task 2 effector system. The results indicate a modulation of SOA effects when the same (oculomotor) Task 1 is combined with a vocal versus a manual Task 2. This is incompatible with the assumption that SOA effects are solely determined by Task 1 response selection duration. Instead, they support the view that dual-task processing bottlenecks are resolved by establishing a capacity allocation scheme fed by multiple input factors, including attentional weights associated with particular effector systems.

Affective distraction along the flexibility-stability continuum

This study explored whether conditions that promote flexibility in task processing enhance the detrimental impact of irrelevant negative stimulation on performance. We approached this flexibility from a transient and a sustained perspective, by manipulating whether participants repeated or switched between two tasks in consecutive trials and whether they performed the tasks in separate blocks or randomly mixed. Participants categorised either a letter or the colour of a bar, which were presented close to an irrelevant negative or neutral picture. Performance was worse in the presence of negative rather than neutral pictures. Repeating or switching tasks transiently did not modulate this detrimental impact of affective distraction in three experiments (n_Exp1 = 32, n_Exp2 = 32, n_Exp3 = 64). Attentional capture by negative content did decline in single compared to mixed task contexts, but only when these sustained task contexts also differed in the frequency of affective stimulation. When affective stimulation was the same in mixed and single task contexts, this modulation vanished. Overall, these results suggest that the influence of task-irrelevant negative stimulation on performance is surprisingly independent of cognitive states that favour either flexible or stable processing of task-relevant information.

Are processing limitations of visual attention and response selection subject to the same bottleneck in dual-tasks?

Visual attention and response selection are processes that are limited by capacity. The present study focuses on whether visual attention is subject to the response selection bottleneck. This was investigated by conducting 2 dual-task experiments of the psychological refractory period (PRP) type. A visual conjunction search task was chosen as Task 2 in these experiments. Conjunction search requires the binding of the stimulus' defining features. This binding is performed in a serial search process in displays of different amounts of stimuli until the presence or absence of the target is correctly indicated. In Experiment 1, the conjunction search was combined with a 2-choice tone discrimination Task 1, and in Experiment 2 with a 2-choice color discrimination Task 1. Detailed reaction time (RT) analyses revealed concurrent performance of visual search to both tone and color in Task 1's response selection. In conclusion, visual attention is not subject to the response selection bottleneck.

Neuroanatomical correlates of awareness of illness in patients with amnestic mild cognitive impairment who will or will not convert to Alzheimer's disease

BACKGROUND

Awareness of cognitive deficits may be reduced in mild cognitive impairment (MCI). This may have a detrimental effect on illness course and may be a predictor of subsequent conversion to AD. Although neuropsychological correlates have been widely investigated, no evidence of a neuroanatomical basis of the phenomenon has been reported yet. This study was aimed at investigating the neuroanatomical correlates of deficit awareness in amnestic MCI to determine whether they constitute risk factors for conversion to AD.

METHOD

A sample of 36 first-diagnosis amnestic MCI patients were followed for five years. At the first diagnostic visit they were administered an extensive diagnostic and clinical procedure and the Memory Insight Questionnaire (MIQ), measuring a total index and four sub-indices, to investigate awareness of deficits in dementia; they also underwent a high resolution T1-weighted Magnetic Resonance Imaging (MRI) investigation. Grey matter brain volumes were analysed on a voxel-by-voxel basis using Statistical Parametric Mapping 8. Data of 10 converter patients (CONV) and those of 26 non converter patients (NOCONV) were analysed using multiple regression models.

RESULTS

At baseline, self-awareness of memory deficits was poorer in CONV compared to NOCONV. Furthermore, reduced awareness of cognitive deficits in CONV correlated with reduced grey matter volume of the anterior cingulate (memory deficit awareness), right pars triangularis of the inferior frontal cortex (memory deficit awareness) and cerebellar vermis (total awareness), whereas in NOCONV it correlated with reduced grey matter volume of left superior (total awareness) and middle (language deficit awareness) temporal areas. Further, at baseline self-awareness of memory deficits were poorer in CONV than in NOCONV.

CONCLUSIONS

Defective awareness of cognitive deficits is underpinned by different mechanisms in CONV and NOCONV amnestic MCI patients. Our data support the hypothesis that poor awareness of cognitive deficit is a predictor of subsequent conversion to AD.

Through the portal: Effect anticipation in the central bottleneck

Ample evidence suggests that motor actions are generated by mentally recollecting their sensory consequences, i.e., via effect anticipations. There is less evidence, though, on the capacity limitations that such effect anticipations suffer from. In the present paper we aim to overcome shortcomings of previous research on this issue by extending the set of empirical indicators of effect anticipations and by using trial-wise instead of block-wise manipulations. In four experiments using the locus of slack- and the effect propagation-logic, we found conclusive evidence for effect anticipation taking place in the capacity-limited central bottleneck. These findings extend previous research suggesting an overlap of a "response selection" process as assumed in traditional stage theory and effect anticipation processes as assumed in effect-based ideomotor models of action control.

Emotional Stroop Dilution: The boundary conditions of attentional capture by threat words

It is widely believed that threatening stimuli in our environment capture attention. Much of the core evidence for attentional capture by threatening stimuli comes from the Emotional Stroop task. Yet recent evidence suggests that the Emotional Stroop task does not measure attentional capture (e.g., Algom et al., 2004). The present paper assesses whether threat words can capture attention using a modified Stroop Dilution procedure (e.g., Kahneman & Chajczyk, 1983), where attentional capture by a threat word is inferred from a reduction in color-word interference for threat words compared to non-threat words (emotional Stroop Dilution). The outcome of the present experiments indicates that threat words can capture attention, but only when task demands do not require that a word be attended. It is suggested that threat words produce (1) cognitive slowing, and influence two processes of selective attention (2) attentional capture and (3) the ability to filter irrelevant dimensions of an attended stimulus.