No Evidence of Suicide Increase Following Terrorist Attacks in the United States: An Interrupted Time‐Series Analysis of September 11 and Oklahoma City

There is substantial evidence of detrimental psychological sequelae following disasters, including terrorist attacks. The effect of these events on extreme responses such as suicide, however, is unclear. We tested competing hypotheses about such effects by employing autoregressive integrated moving average techniques to model the impact of September 11 and the Oklahoma City bombing on monthly suicide counts at the local, state, and national level. Unlike prior studies that provided conflicting evidence, rigorous time series techniques revealed no support for an increase or decrease in suicides following these events. We conclude that while terrorist attacks produce subsequent psychological morbidity and may affect self and collective efficacy well beyond their immediate impact, these effects are not strong enough to influence levels of suicide mortality.     

Cognitive Tendencies in Analogical Forecasting1

This article attempts to identify some cognitive tendencies involved in analogical forecasting of the outcomes of medical treatment. Sixty-one medical doctors were involved in two experimental tasks concerned with prediction of the outcomes of a new medical treatment when the result with a first patient was known to be either negative or positive. The same subjects were also tested by the Short Optimism/Pessimism Questionnaire (SO/PQ) to explore relationships between life attitude and the cognitive tendencies observed in the experiment. The following findings were reported: (1) The first step of forecasting was recognized as a Data Evaluation Process (DEP), where the physician decides if the given data are sufficient to forecast the result of the same treatment with a new patient. (2) Two cognitive tendencies were identified: non-data-suggested tendency—drawing a conclusion opposite to the data given; and data-suggested tendency—drawing an optimistic conclusion when forecasting from “positive” data and a pessimistic conclusion when forecasting from “negative” data. The second tendency appeared to be dominant; however, the “positive” data created a stronger atmosphere to draw conclusions on a negative outcome. (3) It was stated that analogical forecasting involves two integrated processes, i.e., concluding and asserting. If the integration process is not complete, the subject is drawing analogical conclusions with a low confidence. (4) An optimistic life attitude appeared to be an important factor in determining analogical forecasting.     

The effects of objectives and constraints on motor control strategy in reciprocal aiming movements

The goal of this study was to examine how the kinematics of reciprocal aiming movements were affected by both the objective of the movement and the constraints operating on that movement. In Experiment 1, the objective of the movement was indirectly manipulated by capitalizing on the fact that subjects determine their own accuracy and speed limits, despite uniform task instructions to move as quickly and accurately as possible. A Fitts' type reciprocal aiming paradigm was employed, in which 69 subjects were asked to move a stylus repetitively between two spatially separated targets. Four target widths were orthogonally combined with four movement amplitudes, resulting in 16 conditions. Movements were made on an X-Y digitizing tablet. Based on the mean variable error produced on both targets, subjects were differentiated post hoc into three movement objective groups: speed, accuracy, and speed-plus-accuracy. Kinematic analyses revealed that the programming and execution of movements were systematically influenced by both the movement objective and the movement constraints. That is, movement time, peak velocity, dwell time, acceleration and deceleration time, normalized acceleration and normalized deceleration varied systematically as a function of both the speed-accuracy movement objective and the movement constraints of target size and movement distance. Moreover, the consequences of changing the constraints of the movement were affected by an interaction with the objective of the movement. In Experiment 2, the objective of the movement was directly manipulated by varying speed and/or accuracy instructions to subjects. The basic results of Experiment 1 were substantiated. Overall, the results were consistent with the view that motor control is dependent upon sensory consequences.     

Categorical and algebraic aspects of Martin-Löf Type Theory

In the paper there are introduced and discussed the concepts of an indexed category with quantifications and a higher level indexed category to present an algebraic characterization of some version of Martin-Löf Type Theory. This characterization is given by specifying an additional equational structure of those indexed categories which are models of Martin-Löf Type Theory. One can consider the presented characterization as an essentially algebraic theory of categorical models of Martin-Löf Type Theory. The paper contains a construction of an indexed category with quantifications from terms and types of the language of Martin-Löf Type Theory given in the manner of Troelstra [11]. The paper contains also an inductive definition of a valuation of these terms and types in an indexed category with quantifications.     

Dental phobias and anxieties: evidence for conditioning processes in the acquisition and modulation of a learned fear

The present study investigated some of the factors which differentiate individuals with dental anxieties and phobias from those without such fears. In particular, two questions were addressed: (i) What differentiates subjects who have never been anxious about dental treatment from subjects who at some time have been anxious? and (ii) What factors lead to subjects changing their attitudes either from anxious to relaxed or from relaxed to anxious? The results suggest that the factors which influence the acquisition and modulation of dental anxieties are consistent with the associative and representational processes portrayed in contemporary models of human conditioning. Subjects who reported never having had anxieties about dental treatment were less likely to have had a painful dental treatment than subjects who did report an anxiety. Subjects who did report a painful dental experience but did not acquire anxiety reported a history of dental treatment favourable to the operation of latent inhibition. Subjects who reported that they were good at enduring pain were more likely to report a longer interval between their very first dental treatment and their first painful dental treatment. Under some conditions in which latent inhibition should have precluded the acquisition of a dental fear, an anxiety appeared to be acquired because a very painful experience had attenuated the latent inhibition process. Subjects whose dental anxiety did not remit reported significantly more painful and traumatic dental experiences than subjects whose anxiety did remit.     

Sensory preconditioning and UCS inflation in human 'fear' conditioning

This study describes a human electrodermal conditioning experiment involving processes of sensory preconditioning and UCS inflation. In stage 1 of the experiment Ss received six presentations of a CS+ paired with an innocuous 65 dB tone (UCS) and six presentations of an unpaired CS-. In stage 2, Ss in the experimental group had the aversiveness of the UCS inflated as the intensity of the 65 dB tone was increased to 115 dB. In stage 3, Ss were given test presentations of CS+ and CS-. A differential CR to CS+ was found only in stage 3 of the experiment and only in Ss who had experienced the UCS inflation procedure. These results suggest that (i) sensory preconditioning had occurred in stage 1 despite the failure to observe a differential CR in this stage, and (ii) the differential CR observed in stage 3 was mediated by an internal representation of the UCS whose aversiveness had been inflated in stage 2. As well as confirming that processes of sensory preconditioning and UCS inflation can be observed in human as well as animal Ss, these findings have important implications for contemporary conditioning models of clinical fears. In particular, they suggest that a contemporary conditioning model of acquired fears is not bound by the need to discover contiguous stimulus-trauma experiences in the histories of clinical phobias since, in humans at least, processes of stimulus association and UCS revaluation appear to be relatively independent.     

Attention and the order of items in short-term visual memory

Summary Subjects first detected a target presented at the left of fixation, and then attempted to report, in order, the first four items (numerals or shapes) in a stream of items presented to the right of fixation. At comparably difficult presentation rates, 10/s for numerals and 5/s for shapes, reports showed a mixture of correctly ordered items with items reported in a direction opposite to their order of presentation. Reports fit a three-parameter attention-gating model (AGM), which assumes that (1) after target detection, an attention gate opens briefly to allow items to enter visual short-term memory (VSTM), and (2) report order is determined by the attention each item receives in VSTM. Items presented either early or late in the stream tend to receive less attention and are thus reported as later than more central items. The fit to the AGM for both numerals and unlabelled shapes provides evidence that reports reflect order in short-term visual (rather than verbal) memory.This research was supported by USAF grant no. 84-ML-044     

Food anticipation and lever-directed activities in rats

Three experiments are described which elaborate some of the conditions under which rats will contact and manipulate a periodically presented retractable lever. Experiment 1 demonstrated that (i) initial manipulative oral and manual contact with the lever was facilitated if the rat had previous experience of food delivery in the experimental chamber; (ii) persistence in contacting the lever on successive presentations was a function of whether food continued to be presented in the experimental environment; and (iii) food satiation significantly reduced the tendency of the rat to contact the lever even though an expectancy of food had previously been established under conditions of food deprivation. Experiment 2 suggested that the tendency to approach and contact the lever was in part a function of the local moment-to-moment conditional probability of food delivery. Experiment 3 found that the probability of contacting the lever was higher during presentation of an auditory CS signaling a high rate of food delivery than during stimuli signaling no food at all. These results are interpreted as suggesting that the food-signaling aspects of an appetitive CS and that CS's ability to generate signal-directed behaviors are experimentall separable properties.