Inhibitory motor control in stop paradigms: review and reinterpretation of neural mechanisms.

What is the neurophysiological locus of inhibition when preparation for a manual response is countermanded? This paper evaluates data and models that pertain to inhibitory mechanisms operating in stop paradigms. In a model of De Jong, Coles and Logan (1995), (Strategies and mechanisms in nonselective and selective inhibitory motor control. Journal of Experimental Psychology: Human Perception and Performance, 21, 3, 498-511), a mechanism for nonselective inhibition operates peripheral to the motor cortex, while a selective mechanism operates at a central cortical level. We argue, however, that a peripheral mechanism of inhibition is incorrectly inferred from inhibition data available to date. Neurophysiological and psychophysiological data suggest that inhibitory processes always involve the cortex, and inhibitory effects are exerted upstream from the primary motor cortex. The prefrontal cortex and basal ganglia are candidate agents of response inhibition, whereas possible sites of inhibition are the thalamus and motor cortex.     

Investigating global effects in visual occlusion: from a partly occluded square to the back of a tree-trunk.

'Classic' occlusion examples, such as a square partly occluded by a rectangle, have given rise to so-called local and global accounts of amodal completion. Without denying the influence of local configurations, I take the position that, in the long run, any theory of amodal completion should account for global properties. After a brief review of local and global accounts, two extensions of the stimulus domain are proposed to further illustrate the necessity of global accounts. The first is the domain of so-called fuzzy regularities, i.e., regularities which are not based on metrical identities. It is argued and demonstrated that observers are even susceptible to these fuzzy regularities and that they complete partly occluded shapes accordingly. The second extension is towards 3D object completion. Theories of object representation that describe intrinsic regularities of objects appear to be most suitable to predict relative preferences of alternative object completions. Consequently, fuzzy object completions, such as the completion of the back of a tree-trunk, can be explained better by global constraints.     

Brief foveal masking during scene perception

In the present experiment, participants were exploring line drawings of scenes in the context of an object-decision task, while eye-contingent display changes manipulated the appearance of the foveal part of the image. Foveal information was replaced by an ovoid noise mask for 83 ms, after a preset delay of 15, 35, 60, or 85 ms following the onset of fixations. In control conditions, a red ellipse appeared for 83 ms, centered around the fixation position, after the same delays as in the noise-mask conditions. It was found that scene exploration was hampered especially when foveal masking occurred early during fixations, replicating earlier findings. Furthermore, fixation durations were shown to increase linearly as the mask delay decreased, which validates the fixation duration as a measure of perceptual processing speed.     

Avoidant personality disorder and implicit schema-congruent information processing bias: a pilot study with a pragmatic inference task.

Cognitive theory of personality disorders hypothesizes that each personality disorder is characterized by typical maladaptive schemes and that these schemas direct the processing of information resulting in schema-congruent biases. With regard to the avoidant personality disorder, these hypotheses were put to an initial test in a pilot study, using a self-report questionnaire to asses DSM-III-R personality pathology, a belief questionnaire to assess avoidant schemas and a pragmatic inference task to assess schema-congruent implicit attributional bias. Participants were students (n = 57) who scored high or low on DSM-III-R avoidant personality pathology. As predicted from cognitive theory, DSM-III-R avoidant personality pathology was associated with avoidant beliefs (t(45.1) = 4.68, p < 0.001) and avoidant beliefs were associated with schema-congruent information processing bias (t(55) = 2.17, p = 0.02, one-tailed test). However, DSM-III-R avoidant personality pathology was not associated with schema-congruent information processing bias (t(55) = 0.17, p = 0.43, one-tailed test). In addition to avoidant beliefs, low self-esteem was also related to the information processing bias. Social phobia and general personality pathology, two other control variables, were not. The findings warrant further study using the pragmatic inference task in a clinical group.     

Fear relevance and diminution of unconditioned skin conductance responses.

According to Donegan and Wagner's priming model [1987], a signalled UCS will elicit a smaller UCR than an unsignalled UCS. Assuming that fear-relevant CSs are good predictors of aversive UCSs, while fear-irrelevant CSs are relatively bad predictors of aversive UCSs, the present study examined the effect of fear relevance on electrodermal UCR diminution during the acquisition phase of a single cue conditioning procedure. Four groups were studied, each of which consisted of 12 subjects. Group 1 had a fear-relevant CS (a slide of an angry face) paired with a UCS (7 mA shock), whereas group 2 had a fear-irrelevant CS (a slide of a happy face) paired with a UCS. Groups 3 and 4 had unpaired presentations of the CS and UCS and served as control groups for 1 and 2. There were 4 habituation, 8 acquisition, 4 recovery (UCS-only), and 6 extinction (CS-only) trials. While overall UCR levels were lower in the paired than in the unpaired control groups, it was also found that the size of UCR decrement and subsequent recovery was greater in the angry face CS-paired group than in the happy face CS-paired group. This finding is in line with the predictions that flow from the Donegan and Wagner model.     

Predicting Behavior From Actions in the Past: Repeated Decision Making or a Matter of Habit?

This paper summarizes research on determinants of repeated behaviors, and the decision processes underlying them. The present research focuses on travel mode choices as an example of such behaviors. It is proposed that when behavior is performed repeatedly and becomes habitual, it is guided by automated cognitive processes, rather than being preceded by elaborate decision processes (i.e., a decision based on attitudes and intentions). First, current attitude-behavior models are discussed, and the role of habit in these models is examined. Second, research is presented on the decision processes preceding travel mode choices. Based on the present theoretical and empirical overview, it is concluded that frequently performed behavior is often a matter of habit, thereby establishing a boundary condition for the applicability of attitude-behavior models. However, more systematic research is required to disentangle the role of habit in attitude-behavior models and to learn more about the cognitive processes underlying habitual behavior.     

Can the World Help Us in Fixing the Reference of Natural Kind Terms?

According to Putnam the reference of natural kind terms is fixed by the world, at least partly; whether two things belong to the same kind depends on whether they obey the same objective laws. We show that Putnam's criterion of substance identity only “works” if we read “objective laws” as “OBJECTIVE LAWS”. Moreover, at least some of the laws of some of the special sciences have to be included. But what we consider to be good special sciences and what not depends upon our values. Hence, “objective laws” cannot be read as “OBJECTIVE LAWS”. It follows that the reference of natural kind terms cannot be fixed by the world, not even partly. The final conclusion applies to a variety of realisms. This revised version was published online in August 2006 with corrections to the Cover Date.     

The Freedom-based Account of Solidarity and Basic Income

Real-libertarianism, as it is expressed in Philippe Van Parijs' recent monograph Real Freedom for All is characteristically committed to both self-ownership and 'solidarity’ with the infirm or handicapped. In this article it is argued that the conception of (real) freedom that is used to endorse self-ownership is inconsistent with the conception of (social) freedom or opportunity that is used to justify transfer payments to those with no or low earning capacity. The problem turns around the question whether one's freedom consists in the access one has to a share of the social product or in the measure of economic self-sufficiency one enjoys. Accordingly the role of private property in external resources as a condition for freedom is unclear: is it the basis of people's capacity for self-determination or is it the basis of people's bargaining power? Van Parijs' commitment to self-ownership suggests the former, his commitment to solidarity suggests the latter. A similar ambivalence is pointed out in his argument for a universal basic income, for which Real Freedom for All is so well-known.     

Robust canonical discriminant analysis

A method for robust canonical discriminant analysis via two robust objective loss functions is discussed. These functions are useful to reduce the influence of outliers in the data. Majorization is used at several stages of the minimization procedure to obtain a monotonically convergent algorithm. An advantage of the proposed method is that it allows for optimal scaling of the variables. In a simulation study it is shown that under the presence of outliers the robust functions outperform the ordinary least squares function, both when the underlying structure is linear in the variables as when it is nonlinear. Furthermore, the method is illustrated with empirical data.The research of the first author was supported by the Netherlands Organization of Scientific Research (NWO grant 560-267-029).