Evidence for model-based action planning in a sequential finger movement task

In this article, the authors examine whether and how humans use model-free, reflexive strategies and model-based, deliberative strategies in motor sequence learning. They asked subjects to perform the grid-sailing task, which required moving a cursor to different goal positions in a 5 × 5 grid using different key-mapping (KM) rules between 3 finger keys and 3 cursor movement directions. The task was performed under 3 conditions: Condition 1, new KM; Condition 2, new goal position with learned KM; and Condition 3, learned goal position with learned KM; with or without prestart delay time. The performance improvement with prestart delay was significantly larger under Condition 2. This result provides evidence that humans implement a model-based strategy for sequential action selection and learning by using previously learned internal model of state transition by actions.     

Mixing costs in task shifting reflect sequential processing stages in a multicomponent task

We investigated the hypothesis that mixing costs intask shifting reflect th e sequential selection of task components (e.g., stimulus categories) during task execution. This proposition was supported by Hübner, Futterer, and Steinhauser (2001), who showed that the amount of mixing costsdepends on the number of mixed task components (e.g., stimulus level and judgment). However, their results could also be explained by a task set selection account, because task components and task sets were confounded. In Experiments 1 and 2, we compared conditions in which either the number of task sets varied and the number of mixed task components was constant or vice versa. Only the number of mixed task components was predictive for the mixing costs. In Experiment 3, we replicated the additivity of mixing costs from level a ndjudgment mixing. Our results suggest thatthe mixingcosts reflect a selection strategy in which interference is reduced in a stepwise manner.     

Evidence for selective target processing with a low perceptual load flankers task

In this article, we demonstrate that selective target processing is possible when the perceptual load of the task is low. We presented a row of three items with two different identities: one identity for the target letter and one for the two flankers (B. A. Eriksen & C. W. Eriksen, 1974). Such stimulus arrays have been defined as low-load displays (Lavie & Tsal, 1994). We investigated whether subjects could ignore the irrelevant flankers, which were never response alternatives, by manipulating the predictive relationship between the flankers and the response (Miller, 1987). In a high-correlation block, the identity of the flankers was highly predictive of the target identity, whereas in a lowcorrelation block, the predictive value of the flankers was reduced. We varied (1) whether or not the target location was precued, (2) the flanker’s category (digit vs. letter), (3) the target-flanker proximity (near = 3° vs. far = 5°), and (4) the size of the characters. The results indicate that subjects were influenced by the predictive value of near flankers and that the magnitude of this effect was jointly modulated by the target-flanker categorical overlap and by the size of the characters. In contrast, null flanker effects were obtained for far letter flankers in the precue condition, and for far digit flankers, regardless of attentional cuing. These findings (1) are inconsistent with suggestions (Lavie, 1995) that irrelevant stimuli automatically capture attention, and (2) support the notion that target-flanker distinctiveness plays a role when the perceptual load of the task is low.     

Evidence for the automatic processing of prelexical codes in an orthographic but not a phonological task

The automatic activation of phonological and orthographic information in auditory and visual word processing was examined using a task-set procedure. Participants engaged in a phonological task (i.e., determining whether the letter “a” in a word sounded like /e/ or /æ/) or an orthographic task (i.e., determining whether the sound /s/ in a word was spelled with an “s” or a “c”). Participants were cued regarding which task to perform simultaneously with, or 750 ms before, a clear or degraded target. The stimulus clarity effect (i.e., clear words responded to faster than degraded words) was absorbed into the time that it took participants to identify the task on the basis of the cue in a simultaneous cue–target as compared to a delayed cue–target condition, but only for the orthographic task. These data are consistent with the claim that prelexical processing occurs in a capacity-free manner upon stimulus presentation when participants are trying to extract orthographic codes from words presented in the visual and auditory modalities. Such affirmative data were not obtained when participants attempted to extract phonological codes from words, since here the effects of stimulus clarity and cue delay were additive.     

Extrafoveal processing of objects in a naming task: Evidence from word probe experiments

In two experiments, we investigated the processing of extrafoveal objects in a double-object naming task. On most trials, participants named two objects; but on some trials, the objects were replaced shortly after trial onset by a written word probe, which participants had to name instead of the objects. In Experiment 1, the word was presented in the same location as the left object either 150 or 350 msec after trial onset and was either phonologically related or unrelated to that object name. Phonological facilitation was observed at the later but not at the earlier SOA. In Experiment 2, the word was either phonologically related or unrelated to the right object and was presented 150 msec after the speaker had begun to inspect that object. In contrast with Experiment 1, phonological facilitation was found at this early SOA, demonstrating that the speakers had begun to process the right object prior to fixation.     

After effect of seen movement: Evidence for peripheral and central components

Three experiments showed that the movement after-effect (MAE) contains both peripheral and central components. In Experiment I, the left eye viewed a sectored disc rotating to the left, and the right eye viewed a disc rotating to the right, on corresponding retinal areas. Result: when each eye in turn then viewed a stationary disc, the left eye saw a MAE to the right, and the right eye a MAE to the left. These MAE_s must be peripheral.

In Experiment II, it was arranged that the movement information was shared out between the eyes, using a ring of lights which were switched on and off to give rotating phi movement. It was arranged that each eye on its own saw a random flashing oscillation but the two eyes together saw rotation anticlockwise. Result: a clockwise MAE was seen, which must be central.

In Experiment III, the switching programme was modified to arrange that now each eye on its own saw rotation clockwise, but the two eyes together saw rotation anticlockwise. Result: a clockwise MAE was seen, which must be central. (Peripheral MAE_s from each eye on its own would have been anticlockwise.)     

The temporal architecture of central information processing: Evidence for a tentative time-quantum model

Summary A new, elaborated version of a time-quantum model (TQM) is outlined and illustrated by applying it to different experimental paradigms. As a basic prerequisite TQM adopts the coexistence of different discrete time units or (perceptual) intermittencies as constituent elements of the temporal architecture of mental processes. Unlike similar other approaches, TQM assumes the existence of an absolute lower bound for intermittencies, the time-quantum T, as an (approximately) universal constant and which has a duration of approximately 4.5 ms. Intermittencies of TQM must be multiples T _k=k·T ^* within the interval T ^*T _kL·T ^*M·T ^* with T ^*=q·T and integer q, k, L, and M. Here M denotes an upper bound for multipliers characteristic of individuals, the so-called coherence length; q and L may depend on task, individual and other factors. A second constraint is that admissible intermittencies must be integer fractions of L, the operative upper bound. In addition, M is assumed to determine the number of elementary information units to be stored in short-term memory.     

Alerting enhances attentional bias for salient stimuli: Evidence from a global/local processing task

The present study examined the role of alerting in modulating attentional bias to salient events. In a global/local processing task, participants were presented with a large arrow (global level) comprised of smaller arrows (local level) pointing in the same or opposite directions and had to indicate the direction of the large or small arrows in different blocks. Saliency of the global and local levels was manipulated, creating global-salient and local-salient conditions. Alerting signals were presented in half of the trials prior to the target. Results revealed a double dissociation in the effects of alerting on global/local interference effects. In a global salient condition, alerting increased global interference and decreased local interference. In a local salient condition, alerting reduced global interference and increased local interference. We demonstrate that within a single task, alerting can increase and reduce conflict based on perceptual saliency. These findings help to better understand disorders like hemispatial neglect in which both arousal and attention to salient events are impaired. These results also challenge previous theories suggesting that alerting acts to increase conflict interference. We argue that alerting is an adaptive mechanism that diverts attention to salient events, but comes at a cost when selective attention to less salient details is required.     

Evidence for lexical access in a simultaneous matching task

Memory & Cognition - Reaction times in a simultaneous visual matching task were obtained for four types of letter strings: high-frequency words, low-frequency words, orthographically legal...     

Evidence for cerebral asymmetries in a finger sequencing task

Visual input was lateralized using a specially designed contact lens system. Subjects performed a sequence of two keypresses in response to a light stimulus with either the left or the right hand in a choice reaction time paradigm. Two choice reaction time conditions were used: (A) hand certainty, sequence uncertainty and (B) hand uncertainty, sequence certainty. Reaction time (RT) results indicate that there are no significant differences between the left and right hemisphere in selecting a sequential response in either of the two conditions. Interfinger time (IFT) results show a relative left eye (right hemisphere)-left hand advantage when there was hand certainty, sequence uncertainty and a relative left eye (right hemisphere) disadvantage for both hands when there was hand uncertainty, sequence certainty. The RT results do not support the concept of a center in the left hemisphere for selection of the components of a two-element sequential keypress, prior to movement initiation. However, the IFT results indicate that there are differences in the processing ability of the left and right hemispheres in a sequencing task, after movement initiation.     

The relationship between stimulus processing and response selection in the Simon task: Evidence for a temporal overlap

Summary As is indicated by the Simon effect, choice reactions can be carried out faster when the response corresponds spatially to the stimulus, even if the stimulus location is irrelevant to the task. In Experiments 1–4 the relationships between the Simon effect and stimulus eccentricity, signal quality, and signal-background contrast are investigated. The Simon effect was found to interact with all of these factors, at least when manipulated blockwise. These results are at odds with previous results and are difficult to interpret from an additive-factor-method view. An alternative interpretation is suggested that attributes the results to the temporal relationship between the processing of the relevant stimulus information and stimulus location. The assumption is that a decrease in the Simon effect is caused by every experimental manipulation that markedly increases the temporal distance between the coding of the relevant stimulus information and that of the irrelevant stimulus location. This assumption was tested in Experiment 5 in a more direct way. The stimuli were built up on a screen over time, so that the temporal distance between the presence of location and identity information could be controlled experimentally. The results provide further support for a temporal-delay interpretation of interactions between irrelevant stimulus-response correspondence and factors that affect early stages of information processing.     

The activity-set hypothesis for warm-up decrement in a movement balance task

This study investigated the activity-set hypothesis in reducing warm-up decrement. With regard to the hypothesis, it is predicted that warm-up decrement, which is a temporary loss of skill performance following rest, could be reduced if an appropriate reinstating activity were engaged in just prior to the resumption of practice. Seventy-five subjects were given twenty 20-sec tests on the stabilo-meter (criterion task), and then either (a) rested, (b) rested and then performed on interpolated "activity-set" task, or (c) rested and then performed an interpolated "activation" task. All subjects, after receiving one of the three conditions were then retested on the stabilometer for an additional six trials. An analysis of planned comparisons showed that the activity-set interpolated task was effective in reducing warm-up decrement and that activation was not a factor.     

Evidence for transliminality from a subliminal card-guessing task

In this experiment we sought to provide evidence for transliminality from a test of subliminal perception that was disguised as a computerised ESP card-guessing task. It was predicted that highly transliminal individuals would outperform those with low levels of transliminality when given subliminal primes or 'clues' to the correct choice of card, but not when no primes were given. In line with the prediction, higher levels of transliminality were found to be associated with a greater number of correct selections of the target card on the primed trials, but not on the unprimed trials. In addition, a positive correlation was obtained between transliminality and detection accuracy, suggesting that higher levels of transliminality are associated with a greater sensitivity to visual stimulation. The results are discussed with reference to the possibility that transliminality might offer an alternative explanation for some ostensibly psychic perceptual experiences if subliminally acquired material is wrongly attributed to psychic sources.     

Semantic processing in aphasia: Evidence from an auditory lexical decision task

W. Milberg and S. E. Blumstein (1981, Brain and Language 14, 371–385) demonstrated semantic facilitation effects in a visual lexical decision task administered to Wernicke and other aphasics with severe comprehension deficits. In an attempt to explore the generalizability of these findings in a task where the acoustic-phonetic system could not be bypassed to access meaning, Wernicke's, Global, Broca's, and Conduction aphasics were administered a lexical decision task in the auditory modality. The patients were also given a simple semantic judgment task using the word pairs from the lexical decision task. The aphasic patients showed evidence of semantic facilitation whether they were categorized by diagnostic group or comprehension level. Performance of the semantic judgment task correlated with the severity of auditory comprehension deficits, whereas the consistency of the semantic facilitation effect did not. Even patients with severe comprehension deficits showed semantic facilitation. These results decrease the likelihood that auditory comprehension deficits are due to semantic organization per se and increase the likelihood that the deficits lie in one of the many processes involved in access to that information.     

Modeling behavior in a clinically diagnostic sequential risk-taking task

This article models the cognitive processes underlying learning and sequential choice in a risk-taking task for the purposes of understanding how they occur in this moderately complex environment and how behavior in it relates to self-reported real-world risk taking. The best stochastic model assumes that participants incorrectly treat outcome probabilities as stationary, update probabilities in a Bayesian fashion, evaluate choice policies prior to rather than during responding, and maintain constant response sensitivity. The model parameter associated with subjective value of gains correlates well with external risk taking. Both the overall approach, which can be expanded as the basic paradigm is varied, and the specific results provide direction for theories of risky choice and for understanding risk taking as a public health problem.     

Posture based motor planning in a sequential grasping task

Movement planning in sequential tasks is revealed by grasping postures. We explored aspects of planning a sequential drawer opening and object manipulation task with regard to arm and torso postures. We conducted a detailed kinematic analysis of joint postures at the wrist, elbow, and shoulder for a one-grasp and a two-grasp sequence of movement. The second of the two-grasp sequence was constrained (uncomfortable). We predicted that planning for the second grasp in a two-grasp sequence would influence arm, torso, and whole-body postures at the first grasp. Participants prepared for the second grasp by adjusting the posture of the elbow and shoulder and the distance they stepped to the drawer. The joint postures at the elbow and shoulder changed in the direction of the intended object grasp. These findings show that anticipatory adjustments are revealed at postures other than the end-effector and lend insight into the mechanisms of sequential movement planning.     

Gender-specific movement strategies using a computer-pointing task

Females typically demonstrate a movement time advantage for tasks requiring high levels of manual dexterity, whereas males are notably better at targeting activities. According to D. Kimura (2000), the hunter-gatherer hypothesis primarily accounts for those performance advantages; that dichotomy fails, however, when one makes movement outcome predictions for tasks that are not clearly fine-motor or interceptive in nature. Investigators have recently proposed that time constraints (M. Peters, 2005) and gender-specific response style differences (M. Peters & P. Campagnaro, 1996; L. E. Rohr, 2006) affect motor performance. Here, the author used a computer-pointing task measuring both movement error and movement time in 16 participants to further investigate response style differences. Kinematic and linear regression analyses between resultant error and both movement time and task difficulty reinforced the notion that gender-specific movement biases emphasize speed and accuracy, respectively, for men and women.     

Processing two tasks with varying task order: central stage duration influences central processing order

In a recent study, Sigman and Dehaene (2006, PLoS Biology, 4, 1227–1238) reported that perceptual processing duration influences processing order of two tasks in the psychological refractory period paradigm (PRP). The present study examines whether the duration of central processes also influences processing order. For this purpose, we employed letter tasks with different central processing durations and varied task order in the PRP. In one part of the experiment, a tone discrimination task was combined with a similar time-consuming letter discrimination task. In the other part, the tone task was combined with a more time-consuming letter task, which required a mental rotation of the letter thereby prolonging central processing. If the duration of central processes influences processing order, participants should perform the tone task first more often when it is presented with the more time-consuming mental rotation task, than when it is presented with the similar time-consuming letter task. The results clearly confirm this prediction and thus show that not only perceptual processing duration but also central processing duration affects processing order in a dual-task situation. We suggest that the reported effect mirrors a tendency of participants to minimize total reaction time to both tasks by reducing slack time.