Abstract not found

When on the move, cognitive resources are reserved partly for passively monitoring and reacting to contexts and events, and partly for actively constructing them. The Resource Competition Framework (RCF), building on the Multiple Resources Theory, explains how psychosocial tasks typical of mobile situations compete for cognitive resources and then suggests that this leads to the depletion of resources for task interaction and eventually results in the breakdown of fluent interaction. RCF predictions were tested in a semi-naturalistic field study measuring attention during the performance of assigned Web search tasks on mobile phone while moving through nine varied but typical urban situations. Notably, we discovered up to eight-fold differentials between micro-level measurements of attentional resource fragmentation, for example from spans of over 16 seconds in a laboratory condition dropping to bursts of just a few seconds in difficult mobile situations. By calibrating perceptual sampling, reducing resource usage for tasks of secondary importance, and resisting the impulse to switch tasks before finalization, participants compensated for the resource depletion. The findings are compared to previous studies in office contexts. The work is valuable in many areas of HCI dealing with mobility. ACM Classification Keywords: H5.m. Information interfaces and presentation (e.g., HCI): Miscellaneous

Spatial attention: Visual selection and deployment over space The attentional spotlight and spatial cueing Attentional shifts, splits, and resolution Object-based Selection The visual search paradigm Top-down and bottom-up control of attention Inhibitory mechanisms of attention Invalid cueing Negative priming Inhibition of return Temporal attention: Visual selection and deployment over time Single target search Attentional blink and attentional dwell time Repetition blindness NEURAL MECHANISMS OF SELECTION Single-cell physiological method Event-related potentials Functional imaging: PET and fMRI

The authors propose the idea of threaded cognition, an integrated theory of concurrent multitasking—that is, performing 2 or more tasks at once. Threaded cognition posits that streams of thought can be represented as threads of processing coordinated by a serial procedural resource and executed across other available resources (e.g., perceptual and motor resources). The theory specifies a parsimonious mechanism that allows for concurrent execution, resource acquisition, and resolution of resource conflicts, without the need for specialized executive processes. By instantiating this mechanism as a computational model, threaded cognition provides explicit predictions of how multitasking behavior can result in interference, or lack thereof, for a given set of tasks. The authors illustrate the theory in model simulations of several representative domains ranging from simple laboratory tasks such as dual-choice tasks to complex real-world domains such as driving and driver distraction.

The model of a single central bottleneck for human information processing is critically examined. Most evidence cited in support of the model has been observed within the overlapping tasks paradigm. It is shown here that most findings obtained within that paradigm and that were used to support the model are also consistent with a simple resource model. The most prominent findings are the millisecondfor-millisecond slope at the left of the RT2–SOA curve, the high RT1–RT2 correlation, the additivity of the effects on RT2 of SOA and of the difficulty of selecting R2, and the washout of the effect of S2 discriminability on RT2 in a dual-task condition. In addition, the asymmetry of the effects of the dual-task requirement on RT1 and RT2 can be accounted for by the resource model provided that it assumes uneven allocation of resources, which is quite reasonable in view of the task asymmetry inherent in the demand characteristics of the paradigm. The same is true for two other findings that appear to support the single-bottleneck model—that in the dual-task condition, the demand of the first task affects equally RT1 and RT2 and that its effect on RT1 is the same as the corresponding effect in the singletask

against a central bottleneck. This article describes simulations of their Experiments 1 and 4 in the ACT-R cognitive architecture, which does possess a central bottleneck in production execution. The simulation model is capable of accounting for the emergence of near-perfect timesharing in Experiment 1 and the detailed data on the distribution of response times from Experiment 4. With practice, the central bottleneck in ACT-R will be reduced to a maximum of 50 ms (1 production cycle) and can often be much less, depending on timing of stages and variability in their times. The authors also show, with a mathematical analysis of E. Hazeltine et al.’s Experiment 2, that the expected dual costs for these kinds of highly practiced tasks will be small in many circumstances, often under 10 ms. Keywords: dual task, perfect timesharing, ACT-R architecture, central bottleneck Usually, people find it more difficult to perform two tasks at once than to perform a single task, even when the tasks involve different perceptual and response modalities. Such difficulties are often taken as evidence for a central bottleneck (Pashler, 1994; Welford, 1952). Recently, however, Schumacher et al. (2001) provided evidence that with enough practice and with enough

this article should be addressed to Eric Ruthruff, Mailstop 262-4, NASA Ames Research Center, Moffett Field, California 94035. E-mail: eruthruff@mail.arc.nasa.gov Journal of Experimental Psychology: In the public domain Human Perception and Performance 2003, Vol. 29, No. 2, 280--289 DOI: 10.1037/0096-1523.29.2.280 280 necessarily result in substantial interference. The state of affairs envisioned by this hypothesis is shown in Figure 1C. Here, the bottleneck stages (1B and 2B) do not come into conflict, because Stage 1B is completed before Stage 2B is ready to begin (i.e., before Stage 2A has finished)

Humans perform actions to reach particular goals, that is, to intentionally create or modify personally relevant events---we move our eyes to learn more about a novel event, reach for a cup to quench our thirst, and move our lips to share our thoughts with someone else. Accordingly, even primitive actions must involve some kind of planning, some sort of anticipatory control. Indeed, there are at least three defining features that the simplest behavioral acts share with more complex ones. First, all of them are planned in terms of anticipated goal events. In particular, the first step of action planning consists in specifying the features the action is intended to possess; this is achieved by activating the appropriate action-effect codes, i.e., sensory-motor assemblies controlling the production of those features. Action-effect codes emerge through the perception of movement-effect contingencies, and they are acquired from the first months in life on. Besides action planning they are involved in the perception of both one's own actions and actions of others. Second, selected features of an intended action need to be integrated into a coherent, durable action plan, which is achieved by temporarily "binding" distributed feature codes. Third, planning an action turns the cognitive system into a kind of reflex machinery, which facilitates the proper execution of the plan under appropriate circumstances. This involves the implementation of automatic stimulus-response associations and the increase of the salience of action-related situational information, thereby delegating action control to the environment.

The theory of event coding (TEC) is a general framework explaining how perceived and produced events (stimuli and responses) are cognitively represented and how their representations interact to generate perception and action. This article discusses the implications of TEC for understanding the control of voluntary action and makes an attempt to apply, specify, and concretize the basic theoretical ideas in the light of the available research on action control. In particular, it is argued that the major control operations may take place long before a stimulus is encountered (the prepared-reflex principle), that stimulus-response translation may be more automatic than commonly thought, that action selection and execution are more interwoven than most approaches allow, and that the acquisition of action-contingent events (action effects) is likely to subserve both the selection and the evaluation of actions. Life inside and outside of psychological laboratories differs in many ways, which is particularly true with respect to action control. Outside the lab people seem to carry out actions to achieve particular goals and to adapt the environment according to their needs. Once they enter a lab, however, they are commonly talked into responding to arbitrary stimuli by carrying out meaningless movements. The latter is assumed to increase the amount of experimental control over the variables involved in performing an action, which of course is true and utterly important for disentangling all the confounds present in everyday actions. And yet, most models of action control seem to take this highly artificial

this article should be addressed to M.-C. Lien, Mail Stop 262-4, NASA Ames Research Center, Moffett Field, CA 94035 or to R. W. Proctor, Department of Psychological Sciences, Purdue University, West Lafayette, IN 47907 (e-mail: mclien@ mail.arc.nasa.gov or proctor@psych.purdue.edu)