Reaction Time Cost Research Articles

Time reducing process for biofuel production from non edible oil assisted by ultrasonication

Limited resources of conventional fuels such as petrodiesel have led to the search for alternative fuels. Various convention batch/continuous processes for the biodiesel production have been developed before the recent year. All processes are time consuming with high labor cost. Thus, we need a new process for biodiesel production which reduces the reaction time and production cost as well as save the energy. In this work, ultrasonic assisted transesterification of Jatrophacurcas oil is carried out in the presence of methanol and potassium hydroxide (KOH) as catalyst, keeping the molar ratio of oil to alcohol 1:5, catalyst concentration 0.75wt% of oil, ultrasonic amplitude 50% and pulse 0.3 cycle, 7min reaction time under atmospheric condition. Ultrasonic mixing has increased the rate of transesterification reaction as compare to the mechanical mixing.

Developmental change in proactive interference across the life span: Evidence from two working memory tasks.

Working memory (WM) as the ability to temporarily maintain and manipulate various kinds of information is known to be affected by proactive interference (PI) from previously relevant contents, but studies on developmental changes in the susceptibility to PI are scarce. In the present study, we investigated life span development of item-specific PI. To this end, 92 individuals between the ages of 8 and 74 years completed a recent-probes task and an n-back task that both composed experimental manipulations of PI. Regarding global WM development, young adults had higher WM performance than children and older adults in both tasks. Significant PI × Age interactions revealed that susceptibility to PI changed over the life span in both tasks, whereas the developmental course of PI differed between the tasks: Children committed more PI-related errors than young adults in the recent-probes task but showed marginally less PI in the n-back task. Regarding reaction time costs, children did not differ from adults in the recent-probes task and were less affected than adults in the n-back. Older adults showed more PI-related errors than young adults in both tasks. Therefore, as expected, item-specific PI changed over the life span with the young adults being less susceptible to PI than children and older adults. The diverging developmental effects of PI across both tasks, especially in the children, are supposed to reflect different causes for the difficulties regarding resisting PI in children and older adults. These might concern differently developed underlying cognitive processes such as inhibition or recollection, or different responses to task demands across both tasks.

Auditory attentional capture: implicit and explicit approaches

The extent to which distracting items capture attention despite being irrelevant to the task at hand can be measured either implicitly or explicitly (e.g., Simons, Trends Cogn Sci 4:147-155, 2000). Implicit approaches include the standard attentional capture paradigm in which distraction is measured in terms of reaction time and/or accuracy costs within a focal task in the presence (vs. absence) of a task-irrelevant distractor. Explicit measures include the inattention paradigm in which people are asked directly about their noticing of an unexpected task-irrelevant item. Although the processes of attentional capture have been studied extensively using both approaches in the visual domain, there is much less research on similar processes as they may operate within audition, and the research that does exist in the auditory domain has tended to focus exclusively on either an explicit or an implicit approach. This paper provides an overview of recent research on auditory attentional capture, integrating the key conclusions that may be drawn from both methodological approaches.

Bleaching earth clay pH 12.5/PEG-400 catalytic system for synthesis of some novel α, β-unsaturated ketones (chalcones)

We report bleaching earth clay pH 12.5/PEG-400 as an efficient catalytic system for preparation of α,β-unsaturated ketones (chalcones). The method presents one or more advantages over existing methodologies such as shorter reaction time, excellent yield, and low cost. All synthesized products were characterized by spectroscopic and analytical measurements.

Brain Dynamics of Distractibility: Interaction Between Top-Down and Bottom-Up Mechanisms of Auditory Attention

Attention improves the processing of specific information while other stimuli are disregarded. A good balance between bottom-up (attentional capture by unexpected salient stimuli) and top-down (selection of relevant information) mechanisms is crucial to be both task-efficient and aware of our environment. Only few studies have explored how an isolated unexpected task-irrelevant stimulus outside the attention focus can disturb the top-down attention mechanisms necessary to the good performance of the ongoing task, and how these top-down mechanisms can modulate the bottom-up mechanisms of attentional capture triggered by an unexpected event. We recorded scalp electroencephalography in 18 young adults performing a new paradigm measuring distractibility and assessing both bottom-up and top-down attention mechanisms, at the same time. Increasing task load in top-down attention was found to reduce early processing of the distracting sound, but not bottom-up attentional capture mechanisms nor the behavioral distraction cost in reaction time. Moreover, the impact of bottom-up attentional capture by distracting sounds on target processing was revealed as a delayed latency of the N100 sensory response to target sounds mirroring increased reaction times. These results provide crucial information into how bottom-up and top-down mechanisms dynamically interact and compete in the human brain, i.e. on the precarious balance between voluntary attention and distraction.

Strategic flexibility in response preparation: Effects of cue validity on reaction time and pupil dilation

This study examined the ability of participants to strategically adapt their level of response preparation to the predictive value of preparatory cues. Participants performed the finger-precuing task under three levels of cue validity: 100, 75 and 50% valid. Response preparation was indexed by means of reaction time (RT) and pupil dilation, the latter providing a psychophysiological index of invested effort. Results showed a systematic increase in RT benefits (generated by valid cues) and RT costs (generated by invalid cues) with increments in the predictive value of cues. Converging with these behavioural effects, pupil dilation also increased systematically with greater cue validity during the cue-stimulus interval, suggesting more effortful response preparation with increases in cue validity. Together, these findings confirm the hypothesis that response preparation is flexible and that it can be strategically allocated in proportion to the relative frequency of valid/invalid preparatory cues.

Response Suppression Delays the Planning of Subsequent Stimulus-Driven Saccades

The completion of an antisaccade selectively increases the reaction time (RT) of a subsequent prosaccade: a result that has been interpreted to reflect the residual inhibition of stimulus-driven saccade networks [1], [2]. In the present investigation we sought to determine whether the increase in prosaccade RT is contingent on the constituent antisaccade planning processes of response suppression and vector inversion or is limited to response suppression. To that end, in one block participants alternated between pro- and antisaccades after every second trial (task-switching block), and in another block participants completed a series of prosaccades that were randomly (and infrequently) interspersed with no-go catch-trials (go/no-go block). Notably, such a design provides a framework for disentangling whether response suppression and/or vector inversion delays the planning of subsequent prosaccades. As expected, results for the task-switching block showed that antisaccades selectively increased the RTs of subsequent prosaccades. In turn, results for the go/no-go block showed that prosaccade RTs were increased when preceded by a no-go catch-trial. Moreover, the magnitude of the RT ‘cost’ was equivalent across the task-switching and go/no-go blocks. That prosaccades preceded by an antisaccade or a no-go catch-trial produced equivalent RT costs indicates that the conjoint processes of response suppression and vector inversion do not drive the inhibition of saccade planning mechanisms. Rather, the present findings indicate that a general consequence of response suppression is a residual inhibition of stimulus-driven saccade networks.

Comparing movement preparation of unimanual, bimanual symmetric, and bimanual asymmetric movements

The goal of this study was to determine the process or processes most likely to be involved in reaction-time costs for spatially cued bimanual reaching. We used reaction time to measure the cost of bimanual symmetric movements compared to unimanual movements (a bimanual symmetric cost) and the cost for bimanual asymmetric movements compared to symmetric movements (a bimanual asymmetric cost). The results showed that reaction times were comparable for all types of movements in simple reaction time; that is, there was neither a bimanual symmetric cost nor an asymmetric cost. Therefore, unimanual, bimanual symmetric, and bimanual asymmetric movements have comparable complexity during response initiation. In choice conditions, there was no bimanual symmetric cost but there was a bimanual asymmetric cost, indicating that the preparation of asymmetric movements is more complex than symmetric movements. This asymmetric cost is likely the result of interference during response programming.

Zinc iodide: a mild and efficient catalyst for one-pot synthesis of aminoindolizines via sequential A3 coupling/cycloisomerization

ZnI2 was found to be an efficient catalyst for the synthesis of indolizine derivatives by a three-component coupling of pyridine-2-carboxaldehyde/quinoline-2-carboxaldehyde, secondary amines, and terminal alkynes in high yields. This protocol is compatible with a wide range of substrates and is expected to find broad applications due to its operational simplicity, shorter reaction time and low cost. A preliminary photophysical study showed that synthesized morpholinopyrrolo[1,2-a]quinolines represent a new class of fluorophore with high quantum yield.

The Effect of Low versus High Approach-Motivated Positive Affect on Cognitive Control

The motivational dimensional model of affect, proposed by Gable and Harmon-Jones (2010), posits that approach motivational intensity of positive affect modulates the influence of positive affect on cognition. In line with this model, accumulating evidences have supported this hypothesis. Studies have found that low approach-motivated positive affect (e.g., serenity) broadens, whereas high approach-motivated positive affect (e.g., desire) narrows cognitive breadth, such as the breadth of attention, memory, and cognitive categorization. However, little is known about whether the influence of positive affect on cognitive control, which partly reflects the temporality of cognitive processes, is modulated by the approach motivational intensity of positive affect. Therefore, two experiments in this study were conducted to investigate this issue. In experiment 1, a modified stop-signal task was used to explore the influence of approach motivational intensity of positive affect on inhibition control. The stop signal task involved two concurrent tasks, a primary go task and a secondary stop task. The go task was a two-choice reaction time task that required participants to discriminate the location of black squares (2.4 cm × 2.4 cm) positing on the center of the left or right part of the screen. The stop task, which occurred pseudo-randomly and infrequently (25% of the total trials), involved presentation of a red circle (stop signal) that countermanded the go signal by instructing participants to inhibit their planned response to the go task on that trial. Ninety-one undergraduates were randomly assigned to the three conditions: low approach-motivated positive affect (31, 17 females), high approach-motivated positive affect (30, 16 females), and neutral (30, 16 females) conditions. One-way ANOVAs demonstrated that the effects of emotional pictures on response execution and inhibition were significant. Scheffe tests revealed that, relative to the neutral condition, response inhibition was faster in low approach-motivated positive affect condition, while response execution was faster in high approach-motivated positive affect condition. In experiment 2, we used typical numerical classification tasks to examine the influence of approach motivational intensity of positive affect on task switching. Eighty-four new undergraduates (48 females) were randomly assigned to three experimental conditions. Participants had to judge whether a digit (1~9, excluding 5) was smaller or larger than five (smaller–larger task) or whether it was odd or even (odd–even task). We used either a square or diamond frame with sides that were 4.8 cm in length as task cues to indicate the smaller–larger task or odd–even task, respectively. Repeated measures ANOVAs on reaction time and error rate showed that low approach-motivated positive affect facilitated switched task, while high approach-motivated positive affect facilitated repeated task. Results also indicated that low approach-motivated positive affect reduced reaction time and error switch costs, whereas high approach-motivated positive affect increased reaction time switch costs. In summary, this research suggests that low approach-motivated positive affect enhances cognitive flexibility, whereas high approach-motivated positive affect enhances cognitive stability. The current research extends previous work on cognitive breadth to cognitive control which partly reflects the temporality of cognitive processes. Taken together, this line of research suggests that the effects of positive affect on cognitive processes are modulated by its approach motivational intensity.

Prism adaptation does not alter object-based attention in healthy participants

Hemispatial neglect (‘neglect’) is a disabling condition that can follow damage to the right side of the brain, in which patients show difficulty in responding to or orienting towards objects and events that occur on the left side of space. Symptoms of neglect can manifest in both space- and object-based frames of reference. Although patients can show a combination of these two forms of neglect, they are considered separable and have distinct neurological bases. In recent years considerable evidence has emerged to demonstrate that spatial symptoms of neglect can be reduced by an intervention called prism adaptation. Patients point towards objects viewed through prismatic lenses that shift the visual image to the right. Approximately five minutes of repeated pointing results in a leftward recalibration of pointing and improved performance on standard clinical tests for neglect. The understanding of prism adaptation has also been advanced through studies of healthy participants, in whom adaptation to leftward prismatic shifts results in temporary neglect-like performance. Here we examined the effect of prism adaptation on the performance of healthy participants who completed a computerised test of space- and object-based attention. Participants underwent adaptation to leftward- or rightward-shifting prisms, or performed neutral pointing according to a between-groups design. Significant pointing after-effects were found for both prism groups, indicating successful adaptation. In addition, the results of the computerised test revealed larger reaction-time costs associated with shifts of attention between two objects compared to shifts of attention within the same object, replicating previous work. However there were no differences in the performance of the three groups, indicating that prism adaptation did not influence space- or object-based attention for this task. When combined with existing literature, the results are consistent with the proposal that prism adaptation may only perturb cognitive functions for which normal baseline performance is already biased.

Prospective memory in Alzheimer-type dementia: Exploring prospective memory performance in an age-stratified sample

Prospective memory (PM), the memory for future intentions, is an essential component of many day-to-day activities. PM accuracy has consistently been found to decline as a function of age and is further impaired in Alzheimer’s disease (AD). In the present study, subjective PM failures, PM accuracy, and cost of carrying a PM were recorded in 42 healthy elderly, 34 younger old, and 45 older old AD participants. It was found that PM deficits across the AD cohort did not change as a function of age. In addition, while PM accuracy was impaired compared to age-matched controls, cost of carrying a PM intention did not differ across the three groups. Evidence that AD participants show a reaction time (RT) cost of PM intention alongside an impaired PM accuracy indicates that the PM intention is held, but is not implemented effectively. The fact that the cost is independent of age and dementia suggests that it may not index working memory (WM) resource. At a practical level, the study suggests that for a comprehensive evaluation of PM competence cost of carrying a PM intention should be measured alongside PM accuracy.

Does the direction of dimensional changes influence reaction time costs in visual search?

Does the direction of dimensional changes influence reaction time costs in visual search?

Music therapy with moderate Alzheimer's disease in a long-term care center

there was a three-way interaction between task type, switch, and group (p1⁄4 .022): supervets responded faster than controls when switching from the harder color-naming trials to the easier word-naming trials. Whereas controls showed a reaction time cost on these switch trials, supervets showed no reaction time cost. Conclusions: Our results suggest that supervets with many years of high-intensity exercise do not demonstrate robust cognitive benefits from this exercise regime, in comparison with matched controls. Where differences exist, they do not systematically favor the ’supervets’. Further study is needed to determine why long-term exercise regimes may not advantage cognition. One possibility is that long-term highintensity PA affects neuromodulators in ways that offset the advantageous effects seen with short-term exercise.

Evidence for a basic level in a taxonomy of everyday action sounds

We searched for evidence that the auditory organization of categories of sounds produced by actions includes a privileged or "basic" level of description. The sound events consisted of single objects (or substances) undergoing simple actions. Performance on sound events was measured in two ways: sounds were directly verified as belonging to a category, or sounds were used to create lexical priming. The category verification experiment measured the accuracy and reaction time to brief excerpts of these sounds. The lexical priming experiment measured reaction time benefits and costs caused by the presentation of these sounds prior to a lexical decision. The level of description of a sound varied in how specifically it described the physical properties of the action producing the sound. Both identification and priming effects were superior when a label described the specific interaction causing the sound (e.g. trickling) in comparison to the following: (1) more general descriptions (e.g. pour, liquid: trickling is a specific manner of pouring liquid), (2) more detailed descriptions using adverbs to provide detail regarding the manner of the action (e.g. trickling evenly). These results are consistent with neuroimaging studies showing that auditory representations of sounds produced by actions familiar to the listener activate motor representations of the gestures involved in sound production.

Pupil dilation in the Simon task as a marker of conflict processing

Cognitive demands in response conflict paradigms trigger negative affect and avoidance behavior. However, not all response conflict studies show increases in physiological indices of emotional arousal, such as pupil diameter. In contrast to earlier null-results, this study shows for the first time that small (about 0.02 mm) conflict-related pupil dilation can be observed in a Simon task when stimuli do not introduce a light reflex. Results show that response-conflict in Simon trials induces both pupil dilation and reaction-time costs. Moreover, sequential analyses reveal that pupil dilation mirrors the conflict-adaptation pattern observed in reaction time (RT). Although single-trial regression analyses indicated that pupil dilation is likely to reflect more than one process at the same time, in general our findings imply that pupil dilation can be used as an indirect marker of conflict processing.

Attentional decoupling while pursuing intentions: a form of mind wandering?

In the current study, participants performed an ongoing lexical decision task (LDT) in which they had to classify letter strings as words or non-words. In intention conditions, they also had to encode a postponed intention to remember to make a different response if a pre-specified cue appeared. Attempting to replicate an important finding from Cohen et al. (2008), the interest was in examining how varying cognitive load associated with an intention influences attention to the ongoing task (measured by reaction times). Typically, disengaging from a primary task is perceived as negative as it can lead to performance decrements, however, if disengaging from a primary task helps one to accomplish a desired future goal, then these attentional shifts may in fact be constructive. Results replicated those of Cohen et al. (2008) and showed that participants were very flexible in how they managed attention in the ongoing LDT. Reaction time costs emerged when cognitive load was high and solely for word trials (i.e., not for non-word trials). The implications for mind wandering are that, while our attention may wander when stimuli are present that trigger a suspended or unfulfilled goal, we are better able to stay on task when the stimuli are less goal relevant. Therefore, the decoupling process (e.g., Schooler et al., 2011) might be initiated when postponed goals are accompanied by a high degree of cognitive load and when external stimuli are present that relate to that goal.

A Convenient Hydrogenation Method for the Synthesis of Metallo‐mesoporphyrin IX Dimethyl Esters via Self‐catalyzed CoCl2‐NaBH4 Reagent System

AbstractA convenient protocol has been developed for the hydrogenation of metallo‐protoporphyrin IX dimethyl esters (MPPDMEs) to their mesoporphyrin analogues using CoCl2‐NaBH4 reagent system. Metallo‐porphyrin complexes were found to perform as self‐catalysts in this procedure. This method provides several advantages such as safe and simple procedure, short reaction time, high yields and low cost.

The specificity of prospective memory costs

A current issue in the field of prospective memory (i.e., memory for intentions) is the extent to which intentions interfere with ongoing activities. A question of interest is whether this interference is specific to stimuli that are relevant to the intention or whether interference is more general in its influence. Participants performed a lexical decision task (LDT) with an embedded prospective memory (PM) task in which they had to remember to press a computer key if a pre-specified target appeared (e.g., GIRL). Results demonstrated a consistent pattern of results. Increased reaction time costs were observed on trials where there was a match between PM targets and non-target ongoing stimuli. That is, when a prospective memory target was a word, then reaction time costs were observed on non-target word LDT trials and there were no costs on non-target nonword trials. Similarly, if a PM target was a nonword (e.g., UEBL) then costs were observed on non-target nonword LDT trials relative to non-target word trials. Evidence from three experiments suggests that task interference is specific to the type of stimulus (word or nonword) that is relevant to the intention. We refer to this finding as a Stimulus Specific Interference Effect (SSIE).

Hand-held tools with complex kinematics are efficiently incorporated into movement planning and online control

Certain hand-held tools alter the mapping between hand motion and motion of the tool end point that must be controlled in order to perform a task. For example, when using a pool cue, the motion of the cue tip is reversed relative to the hand. Previous studies have shown that the time required to initiate a reaching movement (Fernandez-Ruiz J, Wong W, Armstrong IT, Flanagan JR. Behav Brain Res 219: 8-14, 2011), or correct an ongoing reaching movement (Gritsenko V, Kalaska JF. J Neurophysiol 104: 3084-3104, 2010), is prolonged when the mapping between hand motion and motion of a cursor controlled by the hand is reversed. Here we show that these time costs can be significantly reduced when the reversal is instantiated by a virtual hand-held tool. Participants grasped the near end of a virtual tool, consisting of a rod connecting two circles, and moved the end point to displayed targets. In the reversal condition, the rod translated through, and rotated about, a pivot point such that there was a left-right reversal between hand and end point motion. In the nonreversal control, the tool translated with the hand. As expected, when only the two circles were presented, movement initiation and correction times were much longer in the reversal condition. However, when full vision of the tool was provided, the reaction time cost was almost eliminated. These results indicate that tools with complex kinematics can be efficiently incorporated into sensorimotor control mechanisms used in movement planning and online control.