The apparently deleterious effect of aging on dual-task performance is well established, but there is little agreement about the source of this effect. Studies of the psychological refractory period (PRP) indicate that young adults can flexibly control dual-task performance through task-coordination strategies. Thus, the performance of older adults might differ from young adults because older a...

Why is the human brain fundamentally limited when attempting to execute two tasks at the same time or in close succession? Two classical paradigms, psychological refractory period (PRP) and task switching, have independently approached this issue, making significant advances in our understanding of the architecture of cognition. Yet, there is an apparent contradiction between the conclusions de...

Practice can dramatically reduce dual-task interference, but typically does not eliminate interference entirely. Residual interference after practice is especially large with certain non-preferred modality pairings (e.g., auditory-manual and visual-vocal). Does this residual interference imply the existence of a persistent central-processing bottleneck? To address this question, we transferred ...

In this research, the controversial issue of whether the central bottleneck can be bypassed through task automatization was investigated. To examine this issue, participants received six single-task practice sessions with an auditory-vocal task (low vs. high pitch). We then assessed dual-task performance using the analytically tractable psychological refractory period (PRP) paradigm, in which t...

The authors examined the role of online order control in the psychological refractory period (PRP) paradigm. In the first 2 experiments, participants switched between color-letter and letter-color orders so that subtask order was isolated as the only element being switched. The results indicated that order switching impaired the 2 PRP responses and modulated the PRP effect. Importantly, these e...

The divergent predictions of 2 models of dual-task performance are investigated. The central bottleneck and central capacity sharing models argue that a central stage of information processing is capacity limited, whereas stages before and after are capacity free. The models disagree about the nature of this central capacity limitation. The central bottleneck model claims that central processin...

Some studies suggest that dual-task processing impairs sequence learning; others suggest it does not. The reason for this discrepancy remains obscure. It may have to do with the dual-task procedure often used. Many dual-task sequence learning studies pair the serial reaction time (SRT) task with a tone-counting secondary task. The tone-counting task, however, is not ideal for studying the cogni...

In this paper we give various equivalent characterizations of upper estimates of heat kernels of regular, conservative and local Dirichlet forms on doubling spaces, from both the analytic and probabilistic points of view. The first part of this paper uses purely analytic arguemtn, while the second part focuses on the probabilistic aspects where the exit time plays an important role.