On the evaluation of one-sided evidence

We examine predictions and judgments of confidence based on one-sided evidence. Some subjects saw arguments for only one side of a legal dispute while other subjects (called ‘jurors’) saw arguments for both sides. Subjects predicted the number of jurors who favored the plaintiff in each case. Subjects who saw only one side made predictions that were biased in favor of that side. Furthermore, they were more confident but generally less accurate than subjects who saw both sides. The results indicate that people do not compensate sufficiently for missing information even when it is painfully obvious that the information available to them is incomplete. A simple manipulation that required subjects to evaluate the relative strength of the opponent's side greatly reduced the tendency to underweigh missing evidence.     

Spatial selection in peripheral letter recognition: in search of boundary conditions

Recognition performance for a peripherally presented target letter embedded in a letter string is worse than for targets presented in isolation. This lateral masking effect is commonly attributed to impairments when identifying flanked letters. The hypothesis that also failures during spatial selection of the target underlie lateral masking effects was examined by varying the brightness of the flankers (Experiment 1), by cueing the target position at various times before, during, or after presentation of the string (Experiment 2) and by avoiding the abrupt on- and offset of the flankers (Experiments 3 and 4). Whereas the flankers' brightness had no effect on and cueing only slightly reduced the lateral masking effects, it was substantially reduced by avoiding the abrupt on- and offset of the flankers. The results show that spatial selection is impaired in peripheral vision, and that this is one important factor underlying lateral masking effects.     

Relative damping improves linear mass-spring models of goal-directed movements

A limitation of a simple linear mass-spring model in describing goal directed movements is that it generates rather slow movements when the parameters are kept within a realistic range. Does this imply that the control of fast movements cannot be approximated by a linear system? In servo-control theory, it has been proposed that an optimal controller should control movement velocity in addition to position. Instead of explicitly controlling the velocity, we propose to modify a simple linear mass-spring model. We replaced the damping relative to the environment (absolute damping) with damping with respect to the velocity of the equilibrium point (relative damping). This gives the limb a tendency to move as fast as the equilibrium point. We show that such extremely simple models can generate rapid single-joint movements. The resulting maximal movement velocities were almost equal to those of the equilibrium point, which provides a simple mechanism for the control of movement speed. We further show that peculiar experimental results, such as an 'N-shaped' equilibrium trajectory and the difficulties to measure damping in dynamic conditions, may result from fitting a model with absolute damping where one with relative damping would be more appropriate. Finally, we show that the model with relative damping can be used to model subtle differences between multi-joint interceptions. The model with relative damping fits the data much better than a version of the model with absolute damping.     

Authority conflicts and personality disorders

We investigated personality disorders (PDs) of young men with chronic authority conflicts using the Millon Clinical Multiaxial Inventory-I (MCMI-I; Millon, 1983). PDs occurred considerably more often in the young men with chronic authority conflicts (62%) compared with a clinical control group of young men with acute authority conflicts (39%). The prevalence of PDs in a normal control group was considerably lower (11%). The passive-aggressive PD is over-represented among young men with chronic authority conflicts; there is hardly any antisocial PD. Millon's conceptualization of these disorders could have influenced these results. The high prevalence of passive-aggressive PDs complicates a good psychotherapeutic outcome in young men with chronic authority conflicts. Our results underscore the clinical utility of the controversial PAPD diagnosis.     

An Exploration of Johnson's Sense of ‘Argument’

This essay attempts to give definitions and identity conditions for the two predominant senses of Argument currently in use, the one involving reasons for a conclusion and the other denoting an expressed disagreement with ensuing verbal behaviour by two parties. I see Johnson's new concept of Argument, as developed in his book Manifest Rationality, as a hybrid of the two common senses of Argument, and, accordingly, I try to define and give the identity conditions of Johnson-arguments. Finally, I disagree with Johnson on the nature of the definition he thinks he has proposed, and I conclude with observations suggesting that his logical perspective has dialectical and rhetorical components.