Neural mechanisms of sensitivity to peer information in young adult cannabis users

Though social influence is a critical factor in the initiation and maintenance of marijuana use, the neural correlates of influence in those who use marijuana are unknown. In this study, marijuana-using young adults (MJ; n = 20) and controls (CON; n = 23) performed a decision-making task in which they made a perceptual choice after viewing the choices of unknown peers via photographs, while they underwent functional magnetic resonance imaging scans. The MJ and CON groups did not show differences in the overall number of choices that agreed with versus opposed group influence, but only the MJ group showed reaction time slowing when deciding against group choices. Longer reaction times were associated with greater activation of frontal regions. The MJ goup, compared to CON, showed significantly greater activation in the caudate when presented with peer information. Across groups, caudate activation was associated with self-reported susceptibility to influence. These findings indicate that young adults who use MJ may exhibit increased effort when confronted with opposing peer influence, as well as exhibit greater responsivity of the caudate to social information. These results not only better define the neural basis of social decisions, but also suggest that marijuana use is associated with exaggerated neural activity during decision making that involves social information.     

The impact of MRI scanner environment on perceptual decision-making

Despite the widespread use of functional magnetic resonance imaging (fMRI), few studies have addressed scanner effects on performance. The studies that have examined this question show a wide variety of results. In this article we report analyses of three experiments in which participants performed a perceptual decision-making task both in a traditional setting as well as inside an MRI scanner. The results consistently show that response times increase inside the scanner. Error rates also increase, but to a lesser extent. To reveal the underlying mechanisms that drive the behavioral changes when performing a task inside the MRI scanner, the data were analyzed using the linear ballistic accumulator model of decision-making. These analyses show that, in the scanner, participants exhibit a slow down of the motor component of the response and have less attentional focus on the task. However, the balance between focus and motor slowing depends on the specific task requirements.     

Correction to: Numerals and neural reuse

Synthese - The original publication contained an incorrect copyright holder.     

Meeting the Evil God Challenge

The evil God challenge is an argumentative strategy that has been pursued by a number of philosophers in recent years. It is apt to be understood as a parody argument: a wholly evil, omnipotent and omniscient God is absurd, as both theists and atheists will agree. But according to the challenge, belief in evil God is about as reasonable as belief in a wholly good, omnipotent and omniscient God; the two hypotheses are roughly epistemically symmetrical. Given this symmetry, thesis belief in an evil God and belief in a good God are taken to be similarly preposterous. In this paper, we argue that the challenge can be met, suggesting why the three symmetries that need to hold between evil God and good God – intrinsic, natural theology and theodicy symmetries – can all be broken. As such, we take it that the evil God challenge can be met.     

Alternative Models of Price Behavior in Dyadic Negotiations: Market Prices, Reservation Prices, and Negotiator Aspirations

Three competing predictors of price are manipulated in a two-party distributive negotiation. These include prevailing market prices, negotiator reservation prices, and negotiator aspirations. We offer a cognitive interpretation of how each type of information is incorporated into the negotiator′s thought processes as an alternative cognitive reference point. In two studies varying the levels of these three factors, only reservation prices, not prevailing market prices or negotiator aspirations, account for significant variance in negotiated outcomes. Discussion is offered, suggesting that the negotiator as decision maker may experience a "dominant reference point" effect. When multiple pieces of relevant information are available, the negotiator may only be able to focus on one of them. Among the three predictors studied, the reservation price may be cognitively interpreted as the most absolute limit.     

The psychology of voting action on the psychological origins of electoral research, 1939–1964

This article examines the development of psychologically oriented voting behavior research between 1939–1964. It intends to show the psychological basis of the Columbia and Michigan approaches and its implications for the analysis of electoral behavior. It is argued that, in spite of the large differences commonly perceived between these two approaches, there is much similarity between them, both with regard to their psychological roots as to their principal conclusions.     

Primate head and body restraint without chronic skin openings or attachments to the animal

We developed a primate restraint system that requires no chronic skin openings or attachments to the animal. The restraining chair has a unique neck clasp; monkeys without chains and collars are easily trained to readily enter the chair and accept restraint with the neck and head held at a comfortable angle. A bite bar, in combination with contact on broad areas of the monkey’s brow and occiput, provides rigid head immobilization. In order to achieve contact with a broad area of the occipital bone, the muscles at the back of the animal’s head are surgically detached from the occiput and reattached to the underlying neck muscles. A strain-gauge, mounted on the head-holder and monitored by a laboratory computer, detects head movements of the monkey and permits the experimenter to teach the monkey to sit still during data acquisition. This system is well accepted by experienced monkeys and helps prevent the risks of infection posed by most earlier methods. Furthermore, the head and shoulders of the monkey are readily accessible for examination and for close positioning of test equipment.