Attentional Limitations in Doing Two Tasks at the Same Time

The visible gorilla: Unexpected fast-not physically salient-Objects are noticeable

It is widely believed that observers can fail to notice clearly visible unattended objects, even if they are moving. Here, we created parametric tasks to test this belief and report the results of three high-powered experiments (total n = 4,493) indicating that this effect is strongly modulated by the speed of the unattended object. Specifically, fast-but not slow-objects are readily noticeable, whether they are attended or not. These results suggest that fast motion serves as a potent exogenous cue that overrides task-focused attention, showing that fast speeds, not long exposure duration or physical salience, strongly diminish inattentional blindness effects.

Investigation of the effects of auditory and visual stimuli on attention

Attentional resources limit our perceptual capacities. One vital point is whether these resources are allotted severally to every sense or shared between them. We addressed this problem via means of topics to carry out a dual-task, both in the same modality or other modalities (visual and auditory). The primary task is to count the number of passes of the participants while watching the video that requires visual and auditory attention. Concurrently, they were also asked to notice the pure tones and visual events in the song during the video while counting their pass numbers. The results show that while the auditory task reduced the detection ability visual events task, the dual-task had a significant effect. Previous studies support that tasks requiring simultaneous auditory and visual attention affect each other. Our results have clear implications for showing that performance decreases in dual-task as the perceptual load increases.

Multi-Voiced Music Bypasses Attentional Limitations in the Brain

Attentional limits make it difficult to comprehend concurrent speech streams. However, multiple musical streams are processed comparatively easily. Coherence may be a key difference between music and stimuli like speech, which does not rely on the integration of multiple streams for comprehension. The musical organization between melodies in a composition may provide a cognitive scaffold to overcome attentional limitations when perceiving multiple lines of music concurrently. We investigated how listeners attend to multi–voiced music, examining biological indices associated with processing structured versus unstructured music. We predicted that musical structure provides coherence across distinct musical lines, allowing listeners to attend to simultaneous melodies, and that a lack of organization causes simultaneous melodies to be heard as separate streams. Musician participants attended to melodies in a Coherent music condition featuring flute duets and a Jumbled condition where those duets were manipulated to eliminate coherence between the parts. Auditory–evoked cortical potentials were collected to a tone probe. Analysis focused on the N100 response which is primarily generated within the auditory cortex and is larger for attended versus ignored stimuli. Results suggest that participants did not attend to one line over the other when listening to Coherent music, instead perceptually integrating the streams. Yet, for the Jumbled music, effects indicate that participants attended to one line while ignoring the other, abandoning their integration. Our findings lend support for the theory that musical organization aids attention when perceiving multi–voiced music.

Effects of task probability on prioritized processing: Modulating the efficiency of parallel response selection

Four experiments investigated the extent to which a limited pool of resources can be shared between different tasks performed simultaneously when it is efficient to do so. The experiments used a prioritized processing paradigm, in which stimuli for both a primary task and a background task were presented in each trial. If the primary-task stimulus required a response in a trial, participants made only that response. If the primary-task stimulus did not require a response, participants responded to the background task. The main manipulation was the relative probability that a response would be required to the primary versus background task. In some blocks, the majority of trials required responses to the primary task (Experiments 1 and 2: 80%; Experiments 3 and 4: 60%), whereas in other blocks the majority required responses to the background task. Background-task responses were substantially faster in blocks where they were more likely to be required, consistent with the idea that more capacity was allocated to them in these blocks. Backward compatibility effects on primary-task responses and stimulus-onset asynchrony effects on background-task responses provided further evidence of greater capacity allocation to the background task when there was a higher probability of responding to it. The results support the view that two tasks can be processed in parallel, with resources divided between them, when it is efficient to do so.

Regulation of arousal via online neurofeedback improves human performance in a demanding sensory-motor task

Our state of arousal can significantly affect our ability to make optimal decisions, judgments, and actions in real-world dynamic environments. The Yerkes-Dodson law, which posits an inverse-U relationship between arousal and task performance, suggests that there is a state of arousal that is optimal for behavioral performance in a given task. Here we show that we can use online neurofeedback to shift an individual's arousal from the right side of the Yerkes-Dodson curve to the left toward a state of improved performance. Specifically, we use a brain-computer interface (BCI) that uses information in the EEG to generate a neurofeedback signal that dynamically adjusts an individual's arousal state when they are engaged in a boundary-avoidance task (BAT). The BAT is a demanding sensory-motor task paradigm that we implement as an aerial navigation task in virtual reality and which creates cognitive conditions that escalate arousal and quickly results in task failure (e.g., missing or crashing into the boundary). We demonstrate that task performance, measured as time and distance over which the subject can navigate before failure, is significantly increased when veridical neurofeedback is provided. Simultaneous measurements of pupil dilation and heart-rate variability show that the neurofeedback indeed reduces arousal. Our work demonstrates a BCI system that uses online neurofeedback to shift arousal state and increase task performance in accordance with the Yerkes-Dodson law.

Reduced motor cortex inhibition and a 'cognitive-first' prioritisation strategy for older adults during dual-tasking

It is well established that older adults are less able to perform attentionally demanding motor tasks, placing them at greater risk of accident-related injury. The primary purpose of this study was to investigate whether the interplay between prefrontal and motor cortex activity could predict such age-related performance deficits. Using a dual-task (DT) paradigm, 15 younger and 15 older adults participated in experiment 1, where brain activity was simultaneously measured using functional near infrared spectroscopy (fNIRS) and transcranial magnetic stimulation (TMS). Experiment 1 demonstrated poorer performance for the older group across a range of DTs combining visuomotor arm tracking with a secondary cognitive or motor task. Interestingly however, older adults' DT performance error was isolated to the motor component of DTs. TMS data revealed reduced motor cortex (M1) inhibition during DTs for older adults, and a trend for this correlating with poorer performance. In contrast, poorer performing younger adults showed significantly higher M1 inhibition. Experiment 2 was conducted given a high amount of movement artifact in experiment 1 fNIRS data. Using fNIRS to measure prefrontal, premotor, and motor cortex activity in an additional 15 older adults, we found no evidence of an interplay between these regions predicting DT performance. Nevertheless, performance data replicated experiment 1 in showing that DT error was isolated to motor tasks in older adults, with no significant cognitive task error. Overall, this study shows that older adults seemed to adopt a 'cognitive-first' prioritisation strategy during the DTs involved in our study, and that deficits in DT performance may be related to the modulation of M1 inhibitory mechanisms. We propose that clinicians advise older adults to allocate greater attention to motor tasks during activities where they may be at risk of accident-related injury.

Fear boosts the early neural coding of faces

The rapid extraction of facial identity and emotional expressions is critical for adapted social interactions. These biologically relevant abilities have been associated with early neural responses on the face sensitive N170 component. However, whether all facial expressions uniformly modulate the N170, and whether this effect occurs only when emotion categorization is task-relevant, is still unclear. To clarify this issue, we recorded high-resolution electrophysiological signals while 22 observers perceived the six basic expressions plus neutral. We used a repetition suppression paradigm, with an adaptor followed by a target face displaying the same identity and expression (trials of interest). We also included catch trials to which participants had to react, by varying identity (identity-task), expression (expression-task) or both (dual-task) on the target face. We extracted single-trial Repetition Suppression (stRS) responses using a data-driven spatiotemporal approach with a robust hierarchical linear model to isolate adaptation effects on the trials of interest. Regardless of the task, fear was the only expression modulating the N170, eliciting the strongest stRS responses. This observation was corroborated by distinct behavioral performance during the catch trials for this facial expression. Altogether, our data reinforce the view that fear elicits distinct neural processes in the brain, enhancing attention and facilitating the early coding of faces.

Impaired Error Processing and Semantic Processing During Multitasking

Abstract. Neuronal mechanisms of error processing under multitasking and their impact on the processing of a concurrent task were examined. Twenty-one younger and twenty older healthy adults performed a visual-motor flanker task or an auditory-vocal semantic task or both tasks simultaneously. During task performance the electroencephalogram (EEG) was continuously recorded. The event-related potential (ERP) was derived from the EEG, and ERP components associated with error processing (Ne and Pe) and semantic processing (N400) were analyzed. Older participants responded more slowly than younger ones in the flanker task regardless of the multitasking condition, while accuracy was equal in both groups. In the flanker task, multitasking led to an increase of error rates, a reduction of reaction times, and a disappearance of post-error slowing (PES). Error detection (Ne) was delayed and error awareness (Pe) attenuated in the single flanker task relative to the multitasking condition. In the semantic task, multitasking led to an increase of reaction times and a delay of the N400 in particular when an error in the flanker task occurred. First, these results indicate that multitasking impaired error processing, in particular conscious error perception (Pe) and abolished post-error adjustments of performance (PES) which may have resulted in a more risky response tendency in the flanker task. Second, multitasking impaired semantic processing, in particular after an error in the concurrent flanker task. Hence, multitasking compromised error processing and error prevention in one of the tasks, and semantic processing in the other task. Consequently, multitasking should be avoided at workplaces with error-prone job assignments or where poor understanding of communication may have serious consequences.

Predicting Search Performance in Heterogeneous Visual Search Scenes with Real-World Objects

Previous work in our lab has demonstrated that efficient visual search with a fixed target has a reaction time by set size function that is best characterized by logarithmic curves. Further, the steepness of these logarithmic curves is determined by the similarity between target and distractor items (Buetti et al., 2016). A theoretical account of these findings was proposed, namely that a parallel, unlimited capacity, exhaustive processing architecture is underlying such data. Here, we conducted two experiments to expand these findings to a set of real-world stimuli, in both homogeneous and heterogeneous search displays. We used computational simulations of this architecture to identify a way to predict RT performance in heterogeneous search using parameters estimated from homogeneous search data. Further, by examining the systematic deviation from our predictions in the observed data, we found evidence that early visual processing for individual items is not independent. Instead, items in homogeneous displays seemed to facilitate each other’s processing by a multiplicative factor. These results challenge previous accounts of heterogeneity effects in visual search, and demonstrate the explanatory and predictive power of an approach that combines computational simulations and behavioral data to better understand performance in visual search.

Attentional Limitations in Doing Two Tasks at Once

People generally have difficulty doing two tasks at once. To explain this fact, theorists have proposed that central processing—the thought-like stages following perceptual encoding and preceding response processing—takes place for only one task at a time. Because this bottleneck imposes severe limits on human cognitive processes, research has attempted to find exceptions. There is now solid evidence that, at least in the laboratory, the entire bottleneck can be completely bypassed under favorable combinations of circumstances. While these findings provide a ray of hope for enabling parallel multitasking in real-world scenarios, it will not be easy to take advantage of the combination of conditions that appear to be necessary.

Varieties of Attention

The standard view in cognition is that the identification of visually presented words, up to and including semantic activation, is automatic in various senses. The perspective favored here is that various kinds of attention are intimately involved in the identification of words. Some forms of attention are necessary, whereas others (i.e., executive attention) are recruited to optimize performance. We briefly review results from a variety of literatures that (a) support the latter perspective and (b) are difficult to reconcile with an automatic-processing account.

Does Working Memory Enhance or Interfere With Speech Fluency in Adults Who Do and Do Not Stutter? Evidence From a Dual-Task Paradigm

PURPOSE

The present study examined whether engaging working memory in a secondary task benefits speech fluency. Effects of dual-task conditions on speech fluency, rate, and errors were examined with respect to predictions derived from three related theoretical accounts of disfluencies.

METHOD

Nineteen adults who stutter and twenty adults who do not stutter participated in the study. All participants completed 2 baseline tasks: a continuous-speaking task and a working-memory (WM) task involving manipulations of domain, load, and interstimulus interval. In the dual-task portion of the experiment, participants simultaneously performed the speaking task with each unique combination of WM conditions.

RESULTS

All speakers showed similar fluency benefits and decrements in WM accuracy as a result of dual-task conditions. Fluency effects were specific to atypical forms of disfluency and were comparable across WM-task manipulations. Changes in fluency were accompanied by reductions in speaking rate but not by corresponding changes in overt errors.

CONCLUSIONS

Findings suggest that WM contributes to disfluencies regardless of stuttering status and that engaging WM resources while speaking enhances fluency. Further research is needed to verify the cognitive mechanism involved in this effect and to determine how these findings can best inform clinical intervention.

Two-phase model of the basal ganglia: implications for discontinuous control of the motor system

In this article, I point out that simple one-phase models of the role of the basal ganglia in action selection have a problem. Furthermore, I suggest a solution with major implications for the organization of the action-selection and motor systems. In current models, the striatum evaluates multiple potential actions by adding biases based on previous conditioning. These biases may arise in both the direct (bias for) and indirect (bias against) pathways. Together, these biases influence which action is ultimately chosen. For efficient conditioning to occur, a positive outcome must selectively strengthen the striatal bias for the chosen action (via a dopaminergic mechanism). This is problematic, however, because all potential action choices have influenced firing patterns in striatal cells during the selection process; it is therefore unclear how the synapses that represent the chosen plan could be selectively strengthened. I suggest a simple solution in which the striatum has two functional phases. In the first phase, the basal ganglia provide biases for multiple potential actions (using both the direct and indirect pathways), leading to the choice of a single action in the cortex. In the second phase, an efference copy of the chosen action is sent to the striatum, where it contributes to the establishment of the eligibility trace for that action. This trace, when acted on by subsequent dopaminergic reinforcement, leads to specific strengthening of the bias only for the chosen action. Consistent with this model, recordings show post-choice imposition onto the striatum of signals corresponding to the chosen action. The existence of dual phases of basal ganglia function implies that decisions about action choice are sent to the motor system in a discontinuous manner. This would not be problematic if the motor system also operated discontinuously. I will review evidence suggesting that this is the case, notably that action is organized by approximately 10 Hz oscillations.

Attention and suppression affect tactile perception in reach-to-grasp movements

Reaching with the hand is characterized by a decrease in sensitivity to tactile stimuli presented to the moving hand. Here, we investigated whether tactile suppression can be canceled by attentional orienting. In a first experiment, participants performed a dual-task involving a goal-directed movement paired with the speeded detection of a tactile pulse. The pulse was either delivered to the moving or stationary hand, during movement preparation, execution, or the post-movement phase. Furthermore, stimulation was delivered with equal probability to either hand, or with a higher probability to either the moving or resting hand. The results highlighted faster RTs under conditions of higher probability of stimulation delivery to both moving and resting hands, thus indicating an attentional effect. For the motor preparation period, RTs were faster only at the resting hand under conditions where tactile stimulation was more likely to be delivered there. In a second experiment, a non-speeded perceptual task was used as a secondary task and tactile discrimination thresholds were recorded. Tactile stimulation was delivered concomitantly at both index fingers either in the movement preparation period (both before and after the selection of the movement effector had taken place), in the motor execution period, or, in a control condition, in the time-window of motor execution, but the movement of the hand was restrained. In the preparation period, tactile thresholds were comparable for the two timings of stimulation delivery; i.e., before and after the selection of the movement effector had taken place. These results therefore suggest that shortly prior to, and during, the execution of goal-directed movements, a combined facilitatory and inhibitory influence acts on tactile perception.

Validation of the Personal Need for Structure Scale in Chinese

To validate the Chinese version of the Personal Need for Structure Scale, questionnaires were administered to 1,418 individuals in three samples. Item-total correlations and internal consistency of the scale were acceptable. The test-retest reliability was .79. Confirmatory factor analysis indicated that the Chinese version comprised two dimensions, as did the original version; Desire for Structure and Response to Lack of Structure. Correlation coefficients between the Personal Need for Structure Scale and other related measures indicated that the scale has acceptable discriminant validity and convergent validity.

A hierarchical competing systems model of the emergence and early development of executive function

The hierarchical competing systems model (HCSM) provides a framework for understanding the emergence and early development of executive function--the cognitive processes underlying the conscious control of behavior--in the context of search for hidden objects. According to this model, behavior is determined by the joint influence of a developmentally invariant habit system and a conscious representational system that becomes increasingly influential as children develop. This article describes a computational formalization of the HCSM, reviews behavioral and computational research consistent with the model, and suggests directions for future research on the development of executive function.

Dual-tasking postural control: aging and the effects of cognitive demand in conjunction with focus of attention

Postural control in everyday life is generally accompanied by posture-unrelated cognitive activity. Thus, mild forms of dual-tasking postural control are the norm rather than the exception. Based on this consideration and available evidence, we propose and empirically examined, in young and old adults, a non-monotonic, U-shaped relation between the efficacy of postural control and concurrent cognitive demands that reflect opposing trends of the effects of attention focus and attentional resource competition. When instructed to perform an easy cognitive task that presumably shifted the focus of attention away from posture control, the center of body pressure (COP) excursions decreased both in young and older adults relative to a single-task baseline where the focus of attention was explicitly directed towards the postural control task itself. However, when performing more demanding cognitive tasks, older adults showed increased COP displacements, in line with the predicted U-shape function, whereas young adults did not. We outline mechanisms linking postural control to cognitive demand and suggest routes for future investigation.

Virtually perfect time sharing in dual-task performance: uncorking the central cognitive bottleneck

A fundamental issue for psychological science concerns the extent to which people can simultaneously perform two perceptual-motor tasks. Some theorists have hypothesized that such dual-task performance is severely and persistently constrained by a central cognitive "bottle-neck," whereas others have hypothesized that skilled procedural decision making and response selection for two or more tasks can proceed at the same time under adaptive executive control. The three experiments reported here support this latter hypothesis. Their results show that after relatively modest amounts of practice, at least some participants achieve virtually perfect time sharing in the dual-task performance of basic choice reaction tasks. The results also show that observed interference between tasks can be modulated by instructions about differential task priorities and personal preferences for daring (concurrent) or cautious (successive) scheduling of tasks. Given this outcome, future research should investigate exactly when and how such sophisticated skills in dual-task performance are acquired.

Sharing verbal and visuospatial resources in working memory

A digit memory task and a delayed visual aiming task were used in a test of resource capacity theories. These tasks were run either singly, with short- or long-retention intervals, or in pairs. In the dual-task conditions, the short version of one was inserted into the longer version of the other. Delay by itself had no effect on retention, but the dual-task combinations showed asymmetrical interference: Inserting verbal memory into the visual-motor delay had little effect on either task, but inserting the motor task into the verbal retention interval disrupted both. These results thus support neither single nor multiple resource models, but can be explained with reference to component processes in working memory.