Right-handers' reaching in contralateral hemispace: a kinematic observation

C. Gabbard and C. Helbig (2004) found, when examining seated participants' limb selection for reaching and grasping in hemispace, that right-handers preferred to switch to the nondominant left arm for objects located approximately 20 degrees horizontally from body midline (90 degrees) in left hemispace. In the present study, the authors examined 13 strongly lateralized seated right-handers' kinematics of reaching to object positions ranging from body midline to 40 degrees horizontally in left hemispace. Participants executed faster reaches with the left arm than with the right arm to objects placed 20 degrees-40 degrees from midline, whereas they did not change the proportion of time they spent accelerating the hands when the position of the object changed. A 2nd main finding was an increase in the left hand's trajectory curvature as object position moved farther from midline, with a corresponding decrease in the contribution of upper-arm motion to the reach. Those observations suggest that the switch from dominant right-arm reaching to nondominant left-arm reaching in left hemispace reported in the aforementioned study may have emerged from a shift from a shoulder-driven reach to an elbow-driven action.     

Detection of visual stimuli in correlated noise

The hypothesis of detection by temporal probability summation (TPS) as characterised in Mortensen [(2007). An analysis of visual detection by temporal probability summation, submitted for publication] is critically evaluated, considering data from an experiment of Roufs and Blommaert [(1981). Temporal impulses and step responses of the human eye obtained psychophysically by means of a drift-correcting perturbation technique. Vision Research, 21, 1203-1221], who derived the impulse and the step response for a sustained type of channel. The assumed approximate linearity of the channel is discussed with respect to recent findings from neurophysiological investigations. The data are shown not to be compatible with the TPS-postulate. Further, a model of a cell assembly, consisting of a homogeneous set of neurons, is presented that allows for a natural interpretation of random fluctuations in case of temporal peak detection (TPD). The model may be discussed with respect to TPS as well as to TPD; in any case, the model allows to integrate some results concerning the effects of attentional focussing on the detection process.     

The effects of wording on the understanding and use of uncertainty information in a threshold forecasting decision

Many believe that information about small chances of severe weather would be useful to the general public for precautionary action. What is the best way to explain this kind of information to a non‐expert audience? The studies reported here investigated effects of framing (negative vs. positive), format (frequency vs. probability), likelihood (low vs. high) and compatibility (task‐match) on interpretation of verbal expressions of forecast uncertainty and on subsequent forecasting decisions. The crucial factor was the match between the verbal expression and the overall task goal. Errors increased when there was a mismatch between the expression (e.g. winds less than 20 knots) and the task (e.g. post an advisory when winds will exceed 20 knots). However, framing and format had little impact. We conclude that consideration of user expectations arising from the overall task goal is crucial in explaining uncertainty information to a naïve audience. Global expectations overpower other potential effects. Copyright © 2008 John Wiley & Sons, Ltd.     

Analysis of the Talmudic Argumentum A Fortiori Inference Rule (Kal Vachomer) using Matrix Abduction

We motivate and introduce a new method of abduction, Matrix Abduction, and apply it to modelling the use of non-deductive inferences in the Talmud such as Analogy and the rule of Argumentum A Fortiori. Given a matrix \({\mathbb {A}}\) with entries in {0, 1}, we allow for one or more blank squares in the matrix, say a _i,j =?. The method allows us to decide whether to declare a _i,j = 0 or a _i,j = 1 or a _i,j =? undecided. This algorithmic method is then applied to modelling several legal and practical reasoning situations including the Talmudic rule of Kal-Vachomer. We add an Appendix showing that this new rule of Matrix Abduction, arising from the Talmud, can also be applied to the analysis of paradoxes in voting and judgement aggregation. In fact we have here a general method for executing non-deductive inferences.     

The aftermath of 9/11: effect of intensity and recency of trauma on outcome

Does trauma exposure have a long-term impact on the brain and behavior of healthy individuals? The authors used functional magnetic resonance imaging to assess the impact of proximity to the disaster of September 11, 2001, on amygdala function in 22 healthy adults. More than three years after the terrorist attacks, bilateral amygdala activity in response to viewing fearful faces compared to calm ones was higher in people who were within 1.5 miles of the World Trade Center on 9/11, relative to those who were living more than 200 miles away (all were living in the New York metropolitan area at time of scan). This activity mediated the relationship between group status and current symptoms of posttraumatic stress disorder. In turn, the effect of group status on both amygdala activation (fearful vs. calm faces) and current symptoms was statistically explained by time since worst trauma in lifetime and intensity of worst trauma, as indicated by reported symptoms at time of the trauma. These data are consistent with a model of heightened amygdala reactivity following high-intensity trauma exposure, with relatively slow recovery.     

Decade breaks in the mental number line? Putting the tens and units back in different bins.

Most models of number recognition agree that among other number representations there is a central semantic magnitude representation which may be conceptualized as a logarithmically compressed mental number line. Whether or not this number line is decomposed into different representations for tens and units is, however, controversial. We investigated this issue in German participants in a magnitude comparison (selection) task in which the larger of two visually presented Arabic two-digit numbers had to be selected. Most importantly, we varied unit-decade-compatibility: a number pair was defined as compatible if the decade magnitude comparison and the unit magnitude comparison of the two numbers would lead to the same response (e.g. 52 and 67) and as incompatible if this was not the case (e.g. 47 and 62). While controlling for overall numerical distance, size and other variables, we consistently found compatibility effects. A control experiment showed that this compatibility effect was not due to perceptual presentation characteristics. We conclude that the idea of one single number line representation that does not additionally assume different magnitude representations for tens and units is not sufficient to account for the data. Finally, we discuss why decade effects were not found in other experimental settings.