Involuntary strategy-dependent dual task performance

Previous studies showed that some dual tasks can be performed simultaneously without costs. Yet, a variable SOA between the inputs to such tasks leads to strategic, often involuntary, prioritization of one of the two tasks. Here we explore the boundary conditions for this involuntary or exogenous strategy. In Experiment 1, subjects were initially trained on dual task performance where the input to the two tasks is presented simultaneously (0 SOA). We used two tasks that under such conditions can be performed without costs and indeed subjects displayed perfect sharing of the tasks. Subjects then performed the same two tasks but with a variable SOA (0, 50, 150, 800?ms). This manipulation led to a serial-like performance of the two tasks even in trials with 0 SOA. In Experiment 2, subjects participated in eight sessions. Within each session, they performed in alternation blocks with a fixed 0 SOA and blocks with a variable SOA. Subjects displayed perfect sharing in the pure 0 SOA blocks but performed the two tasks serially in the mixed SOA blocks despite receiving identical instructions. These findings demonstrate that task context is a powerful factor in dual task performance and may lead subjects to involuntarily exhibit dual task costs even in conditions where they can perform the tasks without any costs. Moreover, these findings strongly suggest that costs observed in PRP studies reflect the use of such exogenous strategies rather than a general structural dual task limitation.     

Innovations in computational type theory using Nuprl

For twenty years the Nuprl (“new pearl”) system has been used to develop software systems and formal theories of computational mathematics. It has also been used to explore and implement computational type theory (CTT)—a formal theory of computation closely related to Martin-Löf's intuitionistic type theory (ITT) and to the calculus of inductive constructions (CIC) implemented in the Coq prover.

This article focuses on the theory and practice underpinning our use of Nuprl for much of the last decade. We discuss innovative elements of type theory, including new type constructors such as unions and dependent intersections, our theory of classes, and our theory of event structures.

We also discuss the innovative architecture of Nuprl as a distributed system and as a transactional database of formal mathematics using the notion of abstract object identifiers. The database has led to an independent project called the Formal Digital Library, FDL, now used as a repository for Nuprl results as well as selected results from HOL, MetaPRL, and PVS. We discuss Howe's set theoretic semantics that is used to relate such disparate theories and systems as those represented by these provers.     

Naïve Realism,Hallucination, and Causation: A New Response to the Screening Off Problem

This paper sets out a novel response to the ‘screening off’ problem for naïve realism. The aim is to resist the claim (which many naïve realists accept) that the kind of experience involved in hallucinating also occurs during perception, by arguing that there are causal constraints that must be met if an hallucinatory experience is to occur, ones that are never met in perceptual cases. Notably, given this response, it turns out that, contra current orthodoxy, naïve realists need not adopt any particular view about the psychological nature of hallucinatory experience to handle the screening off problem. Consequently, room opens up for naïve realists to endorse whatever theory of hallucinatory experience seems to best capture the distinctive nature of such episodes.     

Are Fast Complex Movements Unimaginable? Pupillometric Studies of Motor Imagery in Expert Piano Playing

Motor imagery (MI; mental simulation of actions) shares certain mental representations and processes with executed movement (ME). This neurocognitive overlap between MI and ME may explain why the systematic use of MI improves skilled performance in numerous domains. Unfortunately, the attentional mechanisms underlying MI remain unresolved. Therefore, the present studies investigated the role of attentional effort (as measured by pupil dilation) in MI. We evaluated the effects of movement complexity and speed on expert pianists' pupil dilation as they physically executed and used MI to perform easy/complex and slow/fast music phrases. Results revealed that easy movements required similar levels of attentional effort during MI and ME. However, during complex movements performed at a fast speed, the correspondence between execution and imagery of movement was disrupted.     

Initial perceptions in negotiations: evaluation and response to ‘logrolling’ offers

In negotiations, where several issues are under consideration and parties have different priorities among these issues, integrative agreements can be reached through ‘logrolling’: concessions on low priority issues in exchange for gains on higher priority issues. The present research focuses on the potential role of initial offers in the development of integrative agreements. We show first, that in a simulated competitive market the specific composition of initial offers influences the final agreements, beyond the effect predicted by their overall value. In order to obtain some insight into the judgmental processes that might play a role, we explore the way in which inexperienced negotiators presented with a hypothetical negotiation context evaluate and respond to logrolling versus distributive initial offers. Three hypotheses were tested: logrolling offers convey an implicit message of cooperation, logrolling offers promote understanding of the mutual interest structure of the task, and, finally, logrolling offers establish within‐issue anchors. Results do not support the first two hypotheses: logrolling offers were not necessarily judged more attractive than distributive ones, and they did not seem to affect the deeply rooted fixed‐pie assumption. However, initial offers did establish within‐issue anchors: counter‐offers were affected by the specific composition of the initial offers beyond the effect of their overall value. This anchoring process resulted in logrolling offers yielding a higher profit for their initiator, as well as higher combined profits for both parties. Copyright © 2002 John Wiley & Sons, Ltd.     

To go or not to go? Pupillometry elucidates inhibitory mechanisms in motor imagery

Motor imagery (MI) involves consciously performing an action in our minds without engaging in overt physical movement. Although inhibition is crucial to MI, few studies have explored the nature of inhibitory mechanisms underlying this construct. Therefore, little progress has been made in elucidating how or when inhibition is implemented during MI. The present study addressed this unresolved issue by measuring participants’ pupil dilation (an index of attentional effort) as they performed an inhibitory-control (Go/NoGo) procedure in a modified task-switching paradigm. The results showed that inhibitory mechanisms in MI may be implemented via various routes. When MI was the only movement mode used, minimal attentional effort was invested during the Go/NoGo responses, suggesting an early implemented, proactive inhibitory strategy. Conversely, when imagery was preceded by physical movement responses, inhibition required greater attentional effort and it appears as though more active and attention-demanding inhibitory processes must be employed.     

The paradox of decrease and dependent parts

This paper is concerned with the paradox of decrease. Its aim is to defend the answer to this puzzle that was propounded by its originator, namely, the Stoic philosopher Chrysippus. The main trouble with this answer to the paradox is that it has the seemingly problematic implication that a material thing could perish due merely to extrinsic change. (For, intuitively, it is not possible for a mere extrinsic change to cause a material thing to cease to be.) It follows that in order to defend Chrysippus’ answer to the paradox, one has to explain how it could be that Theon is destroyed by the amputation without changing intrinsically. In this paper, I shall answer this challenge by appealing to the broadly Aristotelian idea that at least some of the proper parts of a material substance are ontologically dependent on that substance. I will also appeal to this idea in order to offer a new solution to the structurally similar paradox of increase. In this way, we will end up with a unified solution to two structurally similar paradoxes.     

Reassuring sex: Can sexual desire and intimacy reduce relationship‐specific attachment insecurities?

Past research has shown that attachment orientations shape sexual processes within relationships. Yet, little has been done to explore the opposite direction. In the present research, we examined whether sexual desire and emotional intimacy reduce attachment insecurities over time in emerging relationships. In an 8‐month longitudinal study, we followed 62 newly dating couples across three measurement waves. At Time 1, romantic partners discussed sexual aspects of their relationship and judges coded their displays of sexual desire and intimacy. Participants also completed measures of relationship‐specific attachment anxiety and avoidance in each wave. The results indicated that men's displays of desire predicted a decline in their own and their partner's relationship‐specific insecurities. Conversely, women's displays of desire inhibited the decline in their partner's relationship‐specific insecurities, whereas women's displays of intimacy predicted a decline in their partner's relationship‐specific insecurities. These findings suggest that different sex‐related processes underlie attachment formation in men and women.