Visual and haptic feedback contribute to tuning and online control during object manipulation

The authors employed a virtual environment to investigate how humans use haptic and visual feedback in a simple, rhythmic object-manipulation task. The authors hypothesized that feedback would help participants identify the appropriate resonant frequency and perform online control adjustments. The 1st test was whether sensory feedback is needed at all; the 2nd was whether the motor system combines visual and haptic feedback to improve performance. Task performance was quantified in terms of work performed on the virtual inertia, ability to identify the correct rhythm, and variability of movement. Strict feedforward control was found to be ineffective for this task, even when participants had previous knowledge of the rhythm. Participants (N = 11) performed far better when feedback was available (11 times more work, 2.2 times more precise frequency, 30% less variability; p < .05 for all 3 performance measures). Using sensory feedback, participants were able to rapidly identify 4 different spring-inertia systems without foreknowledge of the corresponding resonant frequencies. They performed over 20% more work with 24% less variability when provided with both visual and haptic feedback than they did with either feedback channel alone (p < .05), providing evidence that they integrated online sensory channels. Whereas feedforward control alone led to poor performance, feedback control led to fast tuning or calibration of control according to the resonant frequency of the object, and to better control of the rhythmic movement itself.     

Identifying and changing the normative beliefs about aggression which lead young Muslim adults to join extremist anti‐Semitic groups in Pakistan

Two studies investigated the role of beliefs about the acceptability of aggression (“normative beliefs”) against Jews in determining who would join an extremist group. In Study 1, students in a university in Pakistan (N=144) completed self‐report attitude measures, and were subsequently approached by a confederate who asked whether they wanted to join an extremist anti‐Semitic organization. Normative beliefs about aggression against Jews were very strong predictors of whether participants agreed to join. In Study 2, participants (N=92) were experimentally assigned to either a brief educational intervention, designed to improve inter‐group relations, or to a control group. They also filled in self‐report attitude measures pre and post intervention. Participants in the intervention group were much less likely to agree to join the extremist group, and this effect of the intervention on joining was mediated by changes in normative beliefs about aggression against Jews. The results have implications for theories of inter‐group aggression and interventions to prevent people from being recruited into extremist groups. Aggr. Behav. 35:514–519, 2009. © 2009 Wiley‐Liss, Inc.     

Neurobiological Markers of Illness Onset in Psychosis and Schizophrenia: The Search for a Moving Target

In this review, we describe neuropsychological and brain imaging findings in the early stages of psychosis and schizophrenia. We focus on recent clinical high-risk studies and consider whether the evidence supports these as ‘endophenotypes’ of a vulnerability to the illness or as ‘biomarkers’ of illness onset and transition. The findings suggest that there are a number of processes at psychosis onset that may represent biomarkers of incipient illness. These neurobiological indices particularly implicate the integrity of frontal and temporal cortices, which may or may not be related to the genetics of psychosis (i.e. potential ‘endophenotypes’). However, these brain regions are dynamically changing during normal maturation, meaning that any putative neurobiological markers identified at the earliest stages of illness may be relatively unstable. We suggest that, while such measures may be readily identified as potential neurobiological markers of established illness, they are inconsistent at (or around) the time of illness onset when assessed cross-sectionally. Instead, identification of more valid risk markers may require longitudinal assessment to ascertain normal or abnormal trajectories of neurodevelopment. Accordingly, we assert that the current conceptualisations of potential biomarkers and/or ‘endophenotypes’ for schizophrenia may need to be reconsidered in the context of normal and abnormal brain maturational processes at the time of onset of psychotic disorders.     

Do Colours Look Like Dispositions? Reply to Langsam and Others

Dispositional theories of colour have been attacked by McGinn and others on the ground that 'Colours do not look like dispositions'. Langsam has argued that on the contrary they do, in 'Why Colours Do Look Like Dispositions', The Philosophical Quarterly , 50 (2000), pp. 68–75. I make three claims. First, neither side has made its case. Secondly, it is true, at least on one interpretation, that colours do not look like dispositions. Thirdly, this does not show that dispositionalism about colours is false.     

Abortion attitudes, 1984-1987-1988: effects of item order and dimensionality.

The comparability of surveys is often hampered by differences in the item order of presentation. The major focus of the present study was to investigate whether a general item or a specific item at the beginning of the questionnaire would affect the endorsement as well as the scalability of a set of attitude items. By using a quasi-A-B-A experimental design for the six abortion items that appeared in the Edmonton Area Survey for the years 1984, 1987, and 1988, we found that the order of presentation of the items affected dramatically the endorsement of the abortion items. Approval of a general item was considerably higher when asked first than when asked after a specific item. In contrast, it was shown by means of a nonparametric item response theory model (the Mokken scale analysis) that the unidimensionality of the six abortion items was not affected by the manipulations of item order (i.e., the six abortion items measured the same concept in the three surveys). It was concluded that the six items are unidimensional and, therefore, create a single scale to measure the change in abortion attitudes across the three periods.     

Generality of a strength model for three conditions of repeated recall

A Markovian model of repeated recall is presented that is based on four memory processes: (a) a presentation increment that strengthens the memory trace of a word when the word is shown to a subject, (b) a recall increment that strengthens the trace when the subject successfully recalls the word, (c) a cueing decrement that weakens the trace as contextual cues for retrieving a word change over successive trials of attempted recall, and (d) a sampling rule that translates the strength of a memory trace into a probability of recall. Mathematically, the model predicts the relative frequencies of the recall patterns that are defined by sequences of recalls and forgets for individual words over trials. According to the model, the recallability of a word depends on its state, which is a function of (a) whether the word has been recalled for the first time, and if so, then (b) how many consecutive forgets of the word immediately precede the current trial, (c) how many successful recalls of the word have accumulated, and (d) how many previous trials of attempted recall have elapsed. Paradigms that were well described by the model were (a) no reminding, in which words were presented once and then recalled repeatedly without additional presentations; (b) restricted reminding, in which words were presented before each trial of attempted recall up to their first successful recall but not thereafter; and (c) complete reminding, in which all words were presented befor each attempted recall, whether previously recalled or not. Differences in recall among these conditions were explained in terms of differences in values of the model's parameters.