Measuring online volitional response control with a continuous tracking task

We present a new tracking task designed to measure elements of response control in particular types of response adjustments such as stopping. In this task, participants track a visual target by manually pressing on a force sensor to yield a trace of force over time. Hardware specifications are detailed, as is an algorithm for determining the latencies of response adjustments such as stopping. We illustrate the use of the task in two experiments. Experiment 1 explores the reliability of data produced by the task. Experiment 2 examines some of the issues that can be addressed using the new task. These results demonstrate the usefulness and potential of the task for gauging response control within the context of the stopping literature.     

Capturing focused attention

When attention is diffuse, as in a visual search task, an abrupt onset almost invariably succeeds in capturing attention. But if attention had been cued in advance to a different location, the same onset may then fail to capture attention (Theeuwes, 1991; Yantis and Jonides, 1990). In previous demonstrations, the onset appeared frequently. This may have diminished the onset's novelty, which in turn could have affected its potency in capturing attention. The question we asked was whether preserving the onset's novelty could enhance its capacity in capturing attention, even when attention had been prioritized elsewhere. As in Theeuwes's (1991) study, observers were cued to the target location with a 100%-predictive central arrow cue. The frequency with which visual transients were introduced was varied across experiments. When the onset stimulus appeared frequently (Experiment 1), it indeed failed to capture attention. But when its appearance was relatively infrequent (Experiment 2), capture effects were clearly observed. In Experiment 3, the target appeared in one location throughout the experiment. This would have improved target localization, but an infrequently appearing onset stimulus still successfully captured attention.     

The processing of spatial frequency and orientation information

Three identification experiments were completed to disambiguate the associations between spatial frequency and orientation information at the sensory, decisional, and response levels. The stimuli were gratings generated by crossing four levels each of spatial frequency and orientation. In Experiment 1, the subjects made a single identification response to the stimuli. In Experiment 2, two identification responses were made, one for the spatial frequency component and the other for the orientation component. In Experiment 3, the subjects identified either the spatial frequency or the orientation component in any block of trials. The data were confusion matrices, and an information-transmission approach was used to investigate the interactions in the system. The results show that although there were sensory associations, there were no interactions at the decisional level. Performance parity was found: there was no significant difference between the single- and double-judgment paradigms in terms of information transmitted. Overall, the results suggest that although spatial frequency and orientation information is coded jointly at the sensory level, subsequent processing is independent, with each dimension drawing upon different attentional resources.     

A test of motor skill-specific action embodiment in ice-hockey players

To further our understanding of the role of the motor system in comprehending action-related sentences, we compared action experts (athletes) to visual experts (fans) and novices when responding with an action-specific effector (either hand or foot). These conditions allowed inferences about the degree and specificity of embodiment in language comprehension. Ice hockey players, fans and novices made speeded judgments regarding the congruence between an auditorily presented sentence and a subsequently presented picture. Picture stimuli consisted of either hockey or everyday items. Half of these pictures ‘matched’ the action implied in the preceding sentence. Further, the action in these images involved either primarily the hand or the foot. For everyday items, action-matched items were responded to faster than action-mismatched items. However, only the players and fans showed the action-match effect for hockey items. There were no consistent effector-stimuli compatibility effects, nor skill-based interactions with compatibility, suggesting that the action-match effect was not based on motor ability per se, but rather a construction of the action based on knowledge or visual experience with the hockey related sentences.     

Movement duration does not affect automatic online control

Pisella et al. (2000) have shown that fast aiming movements are automatically modified on-line in response to a change in target position. Specifically, when a movement is less than 300 ms in duration the reach is completed to a target’s new location even when one never intended to respond to the target jump. In contrast, when movements are slower, the reach is completed according to instructions. At present, it is unclear if it is possible for one’s intentions to guide the initial stages of these slow movements. To determine if the intentional control mechanism can guide the initial stages of a slow aiming movement, participants aimed to targets that could jump at movement onset, with a slow and very slow movement time goal. In particular, participants were to point towards (“pro-point”) or away from (“anti-point”) the target jump, with a movement time goal of 500 or 1200 ms. Results showed that in the anti-point condition, movement trajectories first deviated in the same direction as the target jump, followed by a response in the intended (opposite) direction. This suggests that while movement outcome is controlled by the intentional system, even in these slow aiming movements the automatic system is engaged at movement onset.     

Influence of stimulus–response assignment on the joint-action correspondence effect

Sebanz et al. (Cognition 88:B11–B21, 2003) have shown that spatial correspondence effects are observed even when the two-choice reaction time task is distributed between two people, such that each person is assigned only one of two possible stimulus–response (S–R) pairings. The effect is similar to when one person is assigned and responds to both S–R pairings. These results have been taken to suggest that two people performing a complementary task co-represent each other’s response alternatives. In our experiment, we examined performance when paired participants responded to the same S–R alternative. We reasoned that co-representation would be of little advantage as the task alternatives would be the same for both participants. Correspondence effects were absent when paired participants responded to the same S–R alternative but emerged when they responded to different alternatives.     

Object substitution masking: when does mask preview work?

When a target is enclosed by a 4-dot mask that persists after the target disappears, target identification is worse than it is when the mask terminates with the target. This masking effect is attributed to object substitution masking (OSM). Previewing the mask, however, attenuates OSM. This study investigated specific conditions under which mask preview was, or was not, effective in attenuating masking. In Experiment 1, the interstimulus interval (ISI) between previewed mask offset and target presentation was manipulated. The basic preview effect was replicated; neither ISI nor preview duration influenced target identification performance. In Experiment 2, mask configurations were manipulated. When the mask configuration at preview matched that at target presentation, the preview effect was replicated. New evidence of ineffective mask preview was found: When the two configurations did not match, performance declined. Yet, when the ISI between previewed mask offset and target presentation was removed such that the mask underwent apparent motion, preview was effective despite the configuration mismatch. An interpretation based on object representations provides an excellent account of these data.     

A new object captures attention—but only when you know which objects are old

According to the new object hypothesis (see, e.g., Yantis & Hillstrom, Journal of Experimental Psychology: Human Perception & Performance, 20, 95-107, 1994), an object appearing as a sudden onset captures attention because its appearance demands an immediate updating of visual short-term memory. This hypothesis was tested in three experiments using a procedure that allowed an object to be added to the display but, crucially, without incurring onset transients (Franconeri, Hollingworth, & Simons, Psychological Science, 16, 275-281, 2005). The latter showed that an object inserted in this fashion failed to capture attention. As a test of the new object hypothesis, this procedure assumes that the observers had encoded the display before the new object was introduced. If this assumption is not fulfilled, the new and the old objects cannot be distinguished one from the other. It was, however, unclear whether the encoding had taken place in the Franconeri et al. experiments. We showed that when circumstances were congenial to the encoding of the display before an additional object interposed, then the object successfully captured attention. But when the encoding of the initial display was either difficult or impossible, the additional object failed to capture attention.     

Capturing focused attention

When attention is diffuse, as in a visual search task, an abrupt onset almost invariably succeeds in capturing attention. But if attention had been cued in advance to a different location, the same onset may then fail to capture attention (Theeuwes, 1991; Yantis & Jonides, 1990). In previous demonstrations, the onset appeared frequently. This may have diminished the onset’s novelty, which in turn could have affected its potency in capturing attention. The question we asked was whether preserving the onset’s novelty could enhance its capacity in capturing attention, even when attention had been prioritized elsewhere. As in Theeuwes’s (1991) study, observers were cued to the target location with a 100%-predictive central arrow cue. The frequency with which visual transients were introduced was varied across experiments. When the onset stimulus appeared frequently (Experiment 1), it indeed failed to capture attention. But when its appearance was relatively infrequent (Experiment 2), capture effects were clearly observed. In Experiment 3, the target appeared in one location throughout the experiment. This would have improved target localization, but an infrequently appearing onset stimulus still successfully captured attention.     

Optimal control strategies under different feedback schedules: kinematic evidence

Two experiments were conducted in which participants (N = 12, Experiment 1; N = 12, Experiment 2) performed rapid aiming movements with and without visual feedback under blocked, random, and alternating feedback schedules. Prior knowledge of whether vision would be available had a significant impact on the strategies that participants adopted. When they knew that vision would be available, less time was spent preparing movements before movement initiation. Participants also reached peak deceleration sooner but spent more time after peak deceleration adjusting limb trajectories. Consistent with those findings, analysis of spatial variability at different points in the trajectory indicated that variability increased up to peak deceleration but then decreased from peak deceleration to the end of the movement.