Effects of stimulus probability on reaction time in a number-naming task

Subjects were required to respond to the visual presentation of numerals by uttering syllables closely resembling the names of the numerals. Information in stimulus ensembles was varied by manipulating the number of alternative stimulus configurations that could appear, the relative frequencies of stimuli within an ensemble and the probability of a response being required. An increasing linear function was a good first approximation to the relation between reaction time and information transmission. Systematic deviations from this function were found and an attempt is made to explain them by introducing an intervening variable, “effective probability.”     

Age differences in reaction time and attention in a national telephone sample of adults: education, sex, and task complexity matter

This study demonstrated effects of age, education, and sex on complex reaction time in a large national sample (N = 3,616) with a wide range in age (32-85) and education. Participants completed speeded auditory tasks (from the MIDUS [Midlife in the U.S.] Stop and Go Switch Task) by telephone. Complexity ranged from a simple repeated task to an alternating task that involved central executive processes including attention switching and inhibitory control. Increased complexity was associated with slower responses in older adults, those with lower education, and women, even after controlling for differences in health status. Higher levels of education were associated with greater central executive efficiency across adulthood: Overall, adults with college degrees performed on complex tasks like less educated individuals who were 10 years younger, up to age 75. These findings suggest that advanced education can moderate age differences on complex speeded tasks that require central executive processes, at least up to the point in old age at which biological declines predominate. The approach demonstrates the utility of combining laboratory paradigms with survey methods to enable the study of larger, more diverse and representative samples across the lifespan.     

Effects of changing compatibility relationships on reaction time to the first stimulus in a double-stimulation task

This study investigated the effects of manipulating the response requirement to the second stimulus (S2) on reaction time (RT) to the first stimulus (S1) in a double-stimulation choice RT task. Forty subjects responded to the 100 msec presentation of a left or right light by pressing the key on the same or opposite side as the light. Treatment conditions included a single-stimulation control (no S2 presented), and two double-stimulation conditions each requiring two responses (R1 and R2) in close succession, in one of these latter conditions, the rule governing R2 was the same as that governing R1 while, in the other, the rule governing R2 changed. Results showed the typical double-stimulation effect; i.e., increased latency of R1 when it was followed by S2 - R2. More importantly, R1 latency was increased further when the rules governing R1 and R2 were different. Results are discussed in terms of divided preparation capacity as well as other theories of the psychological refractory period.     

Sustaining visual attention in the face of distraction: a novel gradual-onset continuous performance task

Sustained attention is a fundamental aspect of human cognition and has been widely studied in applied and clinical contexts. Despite a growing understanding of how attention varies throughout task performance, moment-to-moment fluctuations are often difficult to assess. In order to better characterize fluctuations in sustained visual attention, in the present study we employed a novel continuous performance task (CPT), the gradual-onset CPT (gradCPT). In the gradCPT, a central face stimulus gradually transitions between individuals at a constant rate (1,200 ms), and participants are instructed to respond to each male face but not to a rare target female face. In the distractor-present version, the background distractors consist of scene images, and in the distractor-absent condition, of phase-scrambled scene images. The results confirmed that the gradCPT taxes sustained attention, as vigilance decrements were observed over the task’s 12-min duration: Participants made more commission errors and showed increasingly variable response latencies (RTs) over time. Participants’ attentional states also fluctuated from moment to moment, with periods of higher RT variability being associated with increased likelihood of errors and greater speed–accuracy trade-offs. In addition, task performance was related to self-reported mindfulness and the propensity for attention lapses in everyday life. The gradCPT is a useful tool for studying both low- and high-frequency fluctuations in sustained visual attention and is sensitive to individual differences in attentional ability.     

Psychological distance and reaction time in a Stroop task

Several sources of interference may simultaneously affect the onset of the well-known “Stroop effect.” Among them is the semantic component, which is reflected in the gradient or semantic effect. This effect consists of an increase in the amount of interference as the semantic distance between the word and the color concept decreases. Shepard (Science 237:1317–1323, 1987) relates psychological space, measured through multidimensional scaling, to mean response times. The present investigation aims to study the function relating the semantic gradient with the psychological distance between the word and the color in a Stroop task. After measuring the gradient, we obtained the subjective rating of the degree of dissimilarity of the gradient words with the concept of “color.” In our work, we show that the amount of interference in a Stroop task increases when the semantic distance from the word to the color concept decreases, and it does so exponentially. We replicated the study with different stimuli to test the robustness of the results.     

Cardiac activity in a simple reaction time task

Twenty subjects, half having high extraversion and the other half having low extraversion scores on the Eysenck Personality Inventory, performed a simple reaction time task in which the warning stimulus was a light and the imperative stimulus was a tone. Beat-by-beat analysis showed significantly different response patterns between the two groups in time of onset, magnitude, and duration of the cardiac responses. The extraversion measures were found to relate to central-nervous-system-strength types and to indicate relative strength of central inhibitory processes, as reflected by cardiac activity.     

Temporal dynamics in attention bias: effects of sex differences,task timing parameters,and stimulus valence

New methods of calculating indices from the dot-probe task measure temporal dynamics in attention bias or fluctuations in attention bias towards and away from emotional stimuli over time. However, it is unclear how task-specific parameters such as stimulus valence and stimulus onset asynchrony (SOA) as well as participant sex affect temporal dynamics in attention bias. To address this, male and female participants (N?=?106) completed either a fearful or happy face dot-probe task with four levels of SOA (84?ms, 168?ms, 336?ms, and 672?ms). Results suggest that temporal dynamics in attention bias are (1) greatest at the longest SOA, (2) greater in females, and (3) insensitive to stimulus valence. These findings indicate that participant sex and task timing, but not stimulus valence, are related to temporal dynamics in attention bias and should be considered in future studies utilizing this approach.     

A free, easy-to-use, computer-based simple and four-choice reaction time programme: the Deary-Liewald reaction time task

Reaction time tasks are used widely in basic and applied psychology. There is a need for an easy-to-use, freely available programme that can run simple and choice reaction time tasks with no special software. We report the development of, and make available, the Deary-Liewald reaction time task. It is initially tested here on 150 participants, aged from 18 to 80, alongside another widely used reaction time device and tests of fluid and crystallised intelligence and processing speed. The new task’s parameters perform as expected with respect to age and intelligence differences. The new task’s parameters are reliable, and have very high correlations with the existing task. We also provide instructions for downloading and using the new reaction time programme, and we encourage other researchers to use it.     

Orienting of attention: Then and now

It is nearly 35 years since I gave the 7th Sir Frederick Bartlett lecture at Oxford University. This was published as a paper entitled “Orienting of attention in the quarterly journal”. The topic was then primarily in psychology, but now equally often in neuroscience. This paper summarizes the background of the reaction time methods used in the original paper and findings that emerged later on the sensory consequences of orienting, mainly in the visual system. It then discusses the brain network that is the source of the sensory amplification and other brain networks that are involved in attention. Next, it reviews studies of the development of attentional networks in early life. Finally, it indicates how the new tools available to explore the human brain can lead to further progress.     

Span of attention,backward masking,and reaction time

A test pattern consisting of 0 to 15 dots and a following random dot masking pattern were presented for 5 msec each with SOAs varying between 30 and 200 msec. The subject was asked to report the perceived number of dots in the test pattern as soon as possible and to assign a confidence rating to each report. The span of attention (upper limit for 50% correct numerosity judgments) increased from 2.4 to 9.5 as the SOA increased. Backward masking reduced the reported number of dots from the actual number in the test pattern, especially with small SOAs. Reaction time increased linearly at a low rate (approximately 40 msec/dot) up to 4 dots in the test pattern and then increased linearly at a high rate (approximately 370 msec/dot) as thereported, orperceived, number of dots increased. The two different branches of the reaction time curve were considered to represent two separate processes,subitizing andcounting, as suggested by Klahr (1973), who found similar dual increase rates as a function of the actual number of dots. These findings, as well as causal inference based on partial correlations and path analysis, indicated that the reported (perceived) number of dots and confidence rating were both determined by the number of stimulus dots and the SOA and that the reaction time was determined by the so-determined perceived number of dots and level of confidence. A multistage model is proposed.     

The time course of attention in a simple auditory detection task

What is the time course of human attention in a simple auditory detection task? To investigate this question, we determined the detectability of a 20-msec, 1000-Hz tone presented at expected and unexpected times. Twelve listeners who expected the tone to occur at a specific time after a 300-msec narrowband noise rarely detected signals presented 150-375 msec before or 100-200 msec after that expected time. The shape of this temporal-attention window depended on the expected presentation time of the tone and the temporal markers available in the trials. Further, though expecting the signal to occur in silence, listeners often detected signals presented at unexpected times during the noise. Combined with previous data, these results further clarify the listening strategy humans use when trying to detect an expected sound: Humans seem to listen specifically for that sound, while ignoring the background in which it is presented, around the time when the sound is expected to occur.     

The autonomy and focus of attention strategies under distraction: Frequency and sample entropy analyses in a dynamic balance task

An external focus of attention has been shown to be effective in balance tasks. However, replication in applied settings is limited. The OPTIMAL theory proposes that a combination of autonomy and external focus increases focus to the task goal, and therefore more effective than external focus alone. However, research suggests that the combined effect is limited in discrete skills, and the increased focus effect is only reported by subjective assessment. The present study examined the effect of the combined strategy and its effect of “increased focus” compared to external focus and control groups under distraction. In experiment 1, participants (N = 60) practiced eight 35 s trials on a stabilometer followed by a 10 min-delayed retention test and an auditory distraction transfer test. The combined group chose a tape color to place on a stabilometer and was told to “keep the tapes parallel to the floor,” the external focus group was yoked with the combined group, and the control group was told to “do your best”. Performance was measured in Root Mean Square Error (RMSE). The increased focus effect was examined by both subjective (distraction score, a question about participants' perceptions) and objective (Mean Power Frequency, MPF, Sample entropy, SampEn) methods. Although participants improved significantly (p < .05), group differences were not observed during retention (p's > 0.05). An increased focus effect of the combined effect was not observed in any variables (p's > 0.05). In experiment 2, the practice duration was extended to replicate previous study designs (i.e., 90s trials; 2 days of practice; 24 h retention test; the number of participants). Consistent with experiment 1, group differences were not evident in RMSE, SampEn, and MPF (p's > 0.05). We suggest that autonomy may be required to be task-relevant, and simply telling to do best may be as useful as external focus or combined strategies in a continuous balance task. Further, the analysis showed that SampEn increased on Day 1 but decreased on Day 2, and MPF decreased within a session, but the average MPF increased by the day. Potential explanations and future directions when utilizing these metrics are discussed.     

Inhibitory effect of a second stimulus on reaction time to a primary stimulus: a partial successful replication.

A second visual stimulus, to which no response was required, following a primary one lengthened the reaction time to the first stimulus for 25 college students. Reaction time rose as a function of the increase in the interstimulus interval. Duration time of the second stimulus did not affect this response. These results were found under a condition of stimulus-response certainty.     

Effector-related sequence learning in a bimanual-bisequential serial reaction time task

In a bimanual-bisequential version of the serial reaction time (SRT) task participants performed two uncorrelated key-press sequences simultaneously, one with fingers of the left hand and the other with fingers of the right hand. Participants responded to location-based imperative stimuli. When two such stimuli appeared in each trial, the results suggest independent learning of the two sequences and the occurrence of intermanual transfer. Following extended practice in Experiment 2, transfer of acquired sequence knowledge was not complete. Also in Experiment 2, when only one stimulus appeared in each trial specifying the responses for both hands so that there was no basis for separate stimulus-stimulus or separate response-effect learning, independent sequence learning was again evident, but there was no intermanual transfer at all. These findings suggest the existence of two mechanisms of sequence learning, one hand-related stimulus-based and the other motor-based, with only the former allowing for intermanual transfer.     

Initiation of bilateral responses in a kinesthetic reaction time task

Two experiments are presented in which different mechanisms controlling each limb in a bilateral arm response to a unilateral kinesthetic stimulus are postulated to occur. In Experiment 1, the limb serving as the stimulus are postulated to occur. In Experiment 1, the limb serving as the stimulus limb was described as operating with relative invariance by using a tightly coupled input-output reflexive pathway, whereas the nonstimulus limb appeared to be controlled by higher-order processing thought to be more susceptible to influences such as hemispheric specialization and stimulus expectancy. The differential control model was further tested in Experiment 2 by retaining the interhemispheric pathway of the unilateral kinesthetic stimulus but experimentally uncoupling the reflex mechanism from the stimulus side. Analyses of bilateral EMG premotor latencies under these conditions revealed that each response side can be controlled at separate levels-i.e., by a reflexive type mechanism or by higher-order processing when one of the response limbs is also the stimulus limb, both sides reflect behavior that is best described by an information processing type of voluntary control.