Keypress Responses Research Articles

Somatosensory effects of action inhibition: a study with the stop-signal paradigm

When a weak shock is delivered to the finger immediately before a voluntary movement, or during a delay interval where subjects are prepared to make the movement, shock detection rates worsen progressively as the movement approaches. Further, we previously showed that shock detection improves again if a NoGo signal produces inhibition of a prepared response. Here, we used a somatosensory version of the stop-signal paradigm to investigate inhibitory processing during the 'horserace' period when motor excitation and inhibition processes may be simultaneously active. When subjects made a rapid keypress response to a go-signal, shock detection deteriorated in a time-dependent manner, replicating sensory suppression. However, when go-signals were followed by adaptively delayed stop-signals so that subjects could not inhibit the prepared movement, and made errors of commission, we found a paradoxical brief increase in shock detection performance just after the stop-signal, as if in a NoGo trial. During this brief window, the somatosensory system showed a pattern consistent with motor inhibition, even though the motor system itself was too far advanced in movement execution for action to be inhibited. Most models of stop-signal processing propose a two-horse race between excitation and inhibition, with a winner-takes-all solution. We show that there may be distinct motor and somatosensory races. Moreover, inhibitory processes may lead in the somatosensory race, at least briefly, even when excitatory processes win the motor race.

The object-based Simon effect: Grasping affordance or relative location of the graspable part?

Reaction time is often shorter when the irrelevant graspable handle of an object corresponds with the location of a keypress response to the relevant attribute than when it does not. This object-based Simon effect has been attributed to an affordance for grasping the handle with the hand to the same side. Because a grasping affordance should differentially affect keypress responses only when they are made with different hands, we conducted three experiments that measured the object-based Simon effect for frying pan stimuli using between- and within-hand response sets. When the relevant stimulus dimension was color, neither the object-based Simon effect nor the location-based Simon effect varied across response sets. When upright-inverted orientation judgments were made for the frying pan and for nongraspable stimuli derived from it, there again was no significant difference in size of the between- and within-hand Simon effects for any of the stimuli. The results provide evidence that the Simon effect for graspable frying pan stimuli is because of relative location of the handle and not to a grasping affordance.

Mapping Emotion Category Boundaries Using a Visual Expectation Paradigm

Past research showing categorical perception of emotional facial expressions has relied on identification and discrimination tasks that require an explicit response via keypress. Here we report a new paradigm for investigating the category boundary of emotional facial expressions that, instead, relies on an implicit response--eye direction. Participants were trained to expect a target stimulus on a particular side of the monitor, predicted by an emotional expression on a face image. An eye-tracker then recorded eye movements of participants as they viewed novel intermediate facial-expression stimuli. Anticipatory eye movement was taken as evidence of categorisation. Results from two experiments suggest that this implicit method can be used to determine category boundaries, and that the boundaries found with this method are similar to those found with the keypress response.

BDNF, relative preference, and reward circuitry responses to emotional communication

Brain derived neurotrophic factor (BDNF) regulates neural development and synaptic transmission. We have tested the hypothesis that functional variation in the BDNF gene (Val66Met polymorphism, rs6265) affects brain reward circuitry encoding human judgment and decision-making regarding relative preference. We quantified relative preference among faces with emotional expressions (angry, fearful, sad, neutral, and happy) by a keypress procedure performed offline to measure effort traded for viewing time. Keypress-based relative preferences across the ensemble of faces were mirrored significantly by fMRI signal in the orbitofrontal cortex, amygdala, and hippocampus when passively viewing these faces. For these three brain regions, there was also a statistically significant group difference by BDNF genotype in the fMRI responses to the emotional expressions. In comparison with Val/Met heterozygotes, Val/Val individuals preferentially sought exposure to positive emotions (e.g., happy faces) and had stronger regional fMRI activation to aversive stimuli (e.g., angry, fearful, and sad faces). BDNF genotype accounted for approximately 30% of the variance in fMRI signal that mirrors keypress responses to these stimuli. This study demonstrates that functional allelic variation in BDNF modulates human brain circuits processing reward/aversion information and relative preference transactions.

Evidence for an attentional component in saccadic inhibition of return

After presentation of a peripheral cue, facilitation at the cued location is followed by inhibition of return (IOR). It has been recently proposed that IOR may originate at different processing stages for manual and ocular responses, with manual IOR resulting from inhibited attentional orienting, and ocular IOR resulting form inhibited motor preparation. Contrary to this interpretation, we found an effect of target contrast on saccadic IOR. The effect of contrast decreased with increasing reaction times (RTs) for saccades, but not for manual key-press responses. This may have masked the effect of contrast on IOR with saccades in previous studies (Hunt and Kingstone in J Exp Psychol Hum Percept Perform 29:1068-1074, 2003) because only mean RTs were considered. We also found that background luminance strongly influenced the effects of gap and target contrast on IOR.

Visual and tactile action effects determine bimanual coordination performance

Effect-based models of motor control assign a crucial role to anticipated perceptual feedback in action planning. Two experiments were conducted to test the validity of this proposal for discrete bimanual key press responses. The results revealed that the normally observed performance advantage for the preparation of two responses with homologous rather than non-homologous fingers becomes inverted when homologous fingers produce non-identical visual effects, and non-homologous fingers produce identical visual effects. In the second experiment the finger homology effect was strongly reduced when homologous fingers produced non-identical tactile feedback. The results show that representations of to-be-produced visual and tactile action effects both contribute to action planning, though possibly to a varying degree. Implications of these results for effect-based models of motor control are considered.

Reducing and restoring stimulus–response compatibility effects by decreasing the discriminability of location words

In two experiments, we compared level of activation and temporal overlap accounts of compatibility effects in the Simon task by reducing the discriminability of spatial and non-spatial features of a target location word. Participants made keypress responses to the non-spatial or spatial feature of centrally presented location words. The discriminability of the spatial feature of the word (Experiment 1), or of both the spatial and non-spatial feature (Experiment 2), was manipulated. When the spatial feature of the word was task-irrelevant, lowering the discriminability of this feature reduced the compatibility effect. The compatibility effect was restored when the discriminability of both the task-relevant and task-irrelevant features were reduced together. Results provide further evidence for the temporal overlap account of compatibility effects. Furthermore, compatibility effects when the spatial information was task-relevant and those when the spatial information was task-irrelevant were moderately correlated with each other, suggesting a common underlying mechanism in both versions.

Are spatial responses to visuospatial stimuli and spoken responses to auditory letters ideomotor-compatible tasks? Examination of set-size effects on dual-task interference

Previous studies have paired a visual–manual Task 1 with an auditory–vocal Task 2 to evaluate whether the psychological refractory period (PRP) effect is eliminated with two ideomotor-compatible tasks (for which stimuli resemble the response feedback). The present study varied the number of stimulus-response alternatives for Task 1 in three experiments to determine whether set-size and PRP effects were absent, as would be expected if the tasks bypass limited-capacity response-selection processes. In Experiments 1 and 2, the visual–manual task was used as Task 1, with lever-movement and keypress responses, respectively. In Experiment 3, the auditory–vocal task was used as Task 1 and the visual–manual task as Task 2. A significant lengthening of reaction time for 4 vs. 2 alternatives was found for the visual–manual Task 1 and the Task 2 PRP effect in Experiments 1 and 2, suggesting that the visual–manual task is not ideomotor compatible. Neither effect of set size was significant for the auditory–vocal Task 1 in Experiment 3, but there was still a Task 2 PRP effect. Our results imply that neither version of the visual–manual task is ideomotor compatible; other considerations suggest that the auditory–vocal task may also still require response selection.

An action sequence held in memory can interfere with response selection of a target stimulus, but does not interfere with response activation of noise stimuli

Withholding an action plan in memory for later execution can delay execution of another action if the actions share a similar (compatible) action feature (e.g., response hand). We investigated whether this phenomenon, termed compatibility interference (CI), occurs for responses associated with a target as well as responses associated with distractors in a visual selection task. Participants planned and withheld a sequence of keypress responses (with their right or left hand), according to the identity of a stimulus (A), and then immediately executed a keypress response (with their right or left hand) to a second stimulus (B), according to the identity of a target letter appearing alone or among distractor letters. Distractor letters were either response compatible or incompatible with the target and appeared either simultaneously with the target (Experiments 1A and 2) or 100 msec before the target (Experiment 1B). Also, stimulus-response mapping was either 1:1 (Experiment 1) or 2:1 (Experiment 2). Results showed that the response to the Stimulus B target was delayed when it required the same response hand as Stimulus A, as opposed to a different hand. Also, the target reaction time for Stimulus B was greater when the target was flanked by incompatible distractors than when it was flanked by compatible distractors. Moreover, the degree of CI was consistent across the compatible-, incompatible-, and no-distractor conditions, indicating that CI generalizes to responses associated with a target, but not to those associated with distractors. Thus, CI occurs at a response selection, not at a response activation stage. Implications for the code occupation account for CI (e.g., Stoet & Hommel, 1999, 2002) and an alternative account for CI are discussed.

Bimanual Response Grouping in Dual-Task Paradigms

In three experiments we measured response time (RT) and peak force (PF) to investigate the grouping of left- and right-hand key press responses in a dual-task paradigm involving two independent go/no-go tasks. Within each task, a go stimulus within one of two modalities (i.e., visual versus auditory) required a response by one hand. In Experiment 1 with simultaneous go stimuli in the two tasks, responses appeared to be grouped in approximately 75-80% of trials, compared with nearly 100% grouping in a single-task condition requiring bimanual responses to the onset of any stimulus in either modality. In Experiment 2 with stimulus onset asynchronies (SOAs) of 0-400 ms between the two go stimuli, response grouping clearly declined as SOA increased, although some grouping was still evident even at the longest SOA. The same pattern was observed in Experiment 3 with the same range of SOAs but unpredictable stimulus order, suggesting that grouping is not strongly dependent on prior knowledge of the likely response order. These results emphasize the pervasiveness of response grouping in bimanual dual-task RT paradigms and provide useful clues as to its nature.

Short Article: Coding Strategies in Number Space: Memory Requirements Influence Spatial–Numerical Associations

The tendency to respond faster with the left hand to relatively small numbers and faster with the right hand to relatively large numbers ( spatial numerical association of response codes, SNARC effect) has been interpreted as an automatic association of spatial and numerical information. We investigated in two experiments the impact of task-irrelevant memory representations on this effect. Participants memorized three Arabic digits describing a left-to-right ascending number sequence (e.g., 3– 4– 5), a descending sequence (e.g., 5– 4– 3), or a disordered sequence (e.g., 5– 3– 4) and indicated afterwards the parity status of a centrally presented digit (i.e., 1, 2, 8, or 9) with a left/right keypress response. As indicated by the reaction times, the SNARC effect in the parity task was mediated by the coding requirements of the memory tasks. That is, a SNARC effect was only present after memorizing ascending or disordered number sequences but disappeared after processing descending sequences. Interestingly, the effects of the second task were only present if all sequences within one experimental block had the same type of order. Taken together, our findings are inconsistent with the idea that spatial–numerical associations are the result of an automatic and obligatory cognitive process but do suggest that coding strategies might be responsible for the cognitive link between numbers and space.

Motor set modulates automatic priming effects of uninformative cues

In a series of three experiments, we examined facilitatory and inhibitory effects of uninformative spatial cues in a four-choice reaction time (RT) task that required three different types of responses: detection, reaching, and keypressing. Results revealed a pattern of facilitation and inhibition that strongly depended on response mode: Whereas detection and reaching showed longer RTs for cued than uncued locations (reflecting inhibition of return), keypress responses showed shorter RTs for cued than uncued locations (reflecting automatic response activation). Together, these results provide converging evidence for the Grouping model of precuing effects [Adam, J. J., Hommel, B., & Umiltà, C. (2003). Preparing for perception and action (I): The role of grouping in the response-cuing task. Cognitive Psychology, 46, 302–358; Adam, J. J., Hommel, B., & Umiltà, C. (2005). Preparing for perception and action (II): Automatic and effortful processes in response-cuing. Visual Cognition, 12, 1444–1473].

Inhibition of return in single and dual tasks: Examining saccadic, keypress, and pointing responses

Two experiments are reported in which inhibition of return (IOR)was examined wit h single-responsetasks (either manual responses alone or saccadic responses alone) and dual-response tasks (simultaneous manual and saccadic responses). The first experiment-using guided limb movements that require considerable spatial information-showed more IOR for saccades than for pointing responses. In addition, saccadic IOR was reduced with concurrent pointing movements, but manual IOR was not affected by concurrent saccades. Importantly, at the time of saccade initiation, the arm movements did not start yet, indicating that the influence on saccade IOR is due to arm-movement preparation. In the second experiment, using localization keypress responses that required only minimal spatial information, greater IOR was again found for saccadic than for manual responses, but no effect of concurrent movements was found. These findings add further support that there is a dissociation between oculomotor and skeletal-motor IOR. Moreover, the results show that the preparation manual responses tend to mediate saccadic behavior-but only when the manual responses require high levels of spatial accuracy-and that the superior colliculus is the likely neural substrate integrating IOR for eye and arm movements.

Planning keypress and reaching responses: Manipulating number of effectors and preparation interval

This study tested the hypothesis that separate mechanisms mediate the planning of reaching and keypress responses. Participants performed a spatial precueing task with two preparation intervals (100 ms and 1000 ms) and three response sets: (a) pressing one of four response keys; (b) reaching with one of two hands; and (c) reaching with one hand. Reaction time results showed a pattern of precueing effects that strongly depended on the number of effectors in the response set and on the preparation interval. This outcome was interpreted as evidence that distinct mechanisms mediate the planning of multiple-effector and single-effector actions, with effector selection being relevant in the former but not in the latter. The theoretical implications of this conclusion are discussed.

The role of the preSMA and the rostral cingulate zone in internally selected actions

In everyday life, one can differentiate between actions that are primarily internally guided and actions that are primarily guided by external events. FMRI studies investigating the neural correlates of internally guided actions usually report activation maxima in the rostral cingulate zone (RCZ) as well as the preSMA. However, the pertinent contrasts were often confounded by perceptual and motor differences between the different conditions. In the current study, we reinvestigated the neural correlates of internally vs. externally selected actions using a paradigm that avoids any such perceptual or motor confound. By doing so, we wanted to address the yet unsolved question which differential role the preSMA and RCZ play in internally guided actions. Subjects were required to make left or right key presses at the midpoint between isochronous pacing signals (a sequence of 'X's presented to the left or the right of the fixation point). In the internally selected condition, the location of the 'X' was determined by the location of the preceding key press that the subjects selected freely. In the externally selected condition, by contrast, the location of the 'X' prescribed the location of the subsequent key press response. We found that the RCZ was differentially activated by internally as compared to externally selected actions. In contrast to previous studies, the preSMA showed equal activity in both conditions and thus did not differentiate between the two modes of action selection. This suggests a primary role for the RCZ in internally selected actions.

Tracing sequential waves of rapid visuomotor activation in lateralized readiness potentials

Feedforward activation processes are widely regarded as crucial for the automatic initiation of motor responses, whereas recurrent processes are often regarded as crucial for visual awareness. Here, we used a set of behavioral criteria to evaluate whether rapid processing in the human visuomotor system proceeds as would be expected of a feedforward system that works independent of visual awareness. We measured lateralized readiness potentials (LRPs) for key-press responses to color targets (“masks”) preceded by masked color primes mapped onto the same or opposite response, and traced the time-course of motor activation as a function of different prime and mask characteristics. LRP time-courses showed that initial motor activation occurred in prime direction and was time-locked to prime onset. Response activation was then captured on-line by the mask signal, with motor activation now time-locked to the mask and proceeding in mask direction. Crucially, the time-course of early activation by the prime was independent of all mask characteristics. This invariance in early priming effects contrasted with large differences in visual awareness for the prime produced by different masks. Results suggest that primed responses to color stimuli are controlled by feedforward waves of activation sequentially elicited by prime and mask signals traveling rapidly enough to escape the recurrent processes leading to backward masking.

The emergent coordination of cognitive function.

1/f scaling has been observed throughout human physiology and behavior, but its origins and meaning remain a matter of debate. Some argue that it is a byproduct of ongoing processes in the brain or body and therefore of limited relevance to psychological theory. Others argue that 1/f scaling reflects a fundamental aspect of all physiological and cognitive functions, namely, that they emerge in the balance of independent versus interdependent component activities. In 4 experiments, series of key-press responses were used to test between these 2 alternative explanations. The critical design feature was to take 2 measures of each key-press response: reaction time and key-contact duration. These measures resulted in 2 parallel series of intrinsic fluctuations for each series of key-press responses. Intrinsic fluctuations exhibited 1/f scaling in both reaction times and key-contact durations, yet the 2 measures were uncorrelated with each other and separately perturbable. These and other findings indicate that 1/f scaling is too pervasive to be idiosyncratic and of limited relevance. It is instead argued that 1/f scaling reflects the coordinative, metastable basis of cognitive function.

When is an odd number not odd? Influence of task rule on the MARC effect for numeric classification.

When classifying numbers as odd or even with left-right keypresses, performance is better with the mapping even-right/odd-left than with the opposite mapping. This linguistic markedness association of response codes (MARC) effect has been attributed to compatibility between the linguistic markedness of stimulus and response codes. In 2 experiments participants made keypresses to the Arabic numerals or number words 3, 4, 8, and 9 using the odd-even parity rule or a multiple-of-3 rule, which yield the same keypress response for each stimulus. For both stimulus modes, the MARC effect was obtained with the odd-even rule, but tended to reverse with the multiple-of-3 rule. The reversal was complete for the right response, but task rule had little influence on the left response. The results are consistent with the view that the MARC effect and its reversal are caused by correspondence of the stimulus code designated as positive by the task rule with the positive-polarity right response code.

Transfer of noncorresponding spatial associations to the auditory Simon task.

Four experiments examined transfer of noncorresponding spatial stimulus-response associations to an auditory Simon task for which stimulus location was irrelevant. Experiment 1 established that, for a horizontal auditory Simon task, transfer of spatial associations occurs after 300 trials of practice with an incompatible mapping of auditory stimuli to keypress responses. Experiments 2-4 examined transfer effects within the auditory modality when the stimuli and responses were varied along vertical and horizontal dimensions. Transfer occurred when the stimuli and responses were arrayed along the same dimension in practice and transfer but not when they were arrayed along orthogonal dimensions. These findings indicate that prior task-defined associations have less influence on the auditory Simon effect than on the visual Simon effect, possibly because of the stronger tendency for an auditory stimulus to activate its corresponding response.

Differences Between Intention-Based and Stimulus-Based Actions

Abstract: Actions carried out in response to exogenous stimuli and actions selected endogenously on the basis of intentions were compared in terms of their behavioral (movement timing) and electrophysiological (EEG) profiles. Participants performed a temporal bisection task that involved making left or right key presses at the midpoint between isochronous pacing signals (a sequence of centrally-presented letters). In separate conditions, the identity of each letter either (1) prescribed the location of the subsequent key press response (stimulus-based) or (2) was determined by the location of the preceding key press, in which case participants were instructed to generate a random sequence of letters (intention-based). The behavioral results indicated that stimulus-based movements occurred earlier in time than intention-based movements. The EEG results revealed that activity reflecting stimulus evaluation and response selection was most pronounced in the stimulus-based condition, whereas activity associated with the general readiness to act was strongest in the intention-based condition. Together, the behavioral and electrophysiological findings provide evidence for two modes of action planning, one mediated by stimulus-response bindings and the other by action-effect bindings. The comparison of our results to those of an earlier study ( Waszak et al., 2005 ) that employed spatially congruent visuo-motor mappings rather than symbolic visuo-motor mappings suggests that intention-based actions are controlled by similar neural pathways in both cases, but stimulus-based actions are not.