Constraints on the spatiotemporal accuracy of interceptive action: effects of target size on hitting a moving object

Results of two experiments are reported that examined how people respond to rectangular targets of different sizes in simple hitting tasks. If a target moves in a straight line and a person is constrained to move along a linear track oriented perpendicular to the targetrsquos motion, then the length of the target along its direction of motion constrains the temporal accuracy and precision required to make the interception. The dimensions of the target perpendicular to its direction of motion place no constraints on performance in such a task. In contrast, if the person is not constrained to move along a straight track, the targetrsquos dimensions may constrain the spatial as well as the temporal accuracy and precision. The experiments reported here examined how people responded to targets of different vertical extent (height): the task was to strike targets that moved along a straight, horizontal path. In experiment 1 participants were constrained to move along a horizontal linear track to strike targets and so target height did not constrain performance. Target height, length and speed were co-varied. Movement time (MT) was unaffected by target height but was systematically affected by length (briefer movements to smaller targets) and speed (briefer movements to faster targets). Peak movement speed (Vmax) was influenced by all three independent variables: participants struck shorter, narrower and faster targets harder. In experiment 2, participants were constrained to move in a vertical plane normal to the targetrsquos direction of motion. In this task target height constrains the spatial accuracy required to contact the target. Three groups of eight participants struck targets of different height but of constant length and speed, hence constant temporal accuracy demand (different for each group, one group struck stationary targets = no temporal accuracy demand). On average, participants showed little or no systematic response to changes in spatial accuracy demand on any dependent measure (MT, Vmax, spatial variable error). The results are interpreted in relation to previous results on movements aimed at stationary targets in the absence of visual feedback.

MDMA (Ecstasy) neurotoxicity: assessing and communicating the risks

MDMA (3,4-methylenedioxymethamphetamine) is an amphetamine analogue that produces euphoric and stimulant effects and a feeling of closeness towards others.1 and 2 For more than a decade, MDMA (colloquially known as “Ecstasy” or “E”) has been widely used by young adults as a dance-party drug. The usual recreational oral dose is 1-2 tablets (each containing about 60-120 mg of MDMA) a standard oral dose of 0·75–4·00 mg per kg in 60–80 kg people. MDMA is typically used once fortnightly or less because tolerance to the effects of MDMA develops rapidly. More frequent use requires larger doses to achieve the desired effects, but this increases the prevalence of unpleasant side-effects.3 A number of deaths have occurred as a result of malignant hyperthermia or idiosyncractic reactions to the drug, but these have been rare.4 MDMA is perceived by many users to be a safe drug.1 Few report the craving associated with opiates or cocaine3 and most MDMA users are aware of only mild and transient disruptions of functioning.3 and 5 AC Parrott and J Lasky, Ecstasy (MDMA) effects upon mood and cognition: before, during and after a Saturday night dance, Psychopharmacology 139 (1998), pp. 261–268. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (174)5 The perceived safety of MDMA is at odds with animal evidence of MDMA neurotoxicity, an increasing prevalence of hazardous patterns of use among recreational MDMA users, and emerging evidence of neurotoxicity among heavier MDMA users.

The effects of change in lead stimulus modality on the modulation of acoustic blink startle

In two experiments we investigated the effect of generalized orienting induced by changing the modality of the lead stimulus on the modulation of blink reflexes elicited by acoustic stimuli. In Experiment 1 (n = 32), participants were presented with acoustic or visual change stimuli after habituation training with tactile lead stimuli. In Experiment 2 (n = 64), modality of the lead stimulus (acoustic vs. visual) was crossed with experimental condition (change vs. no change). Lead stimulus change resulted in increased electrodermal orienting in both experiments. Blink latency shortening and blink magnitude facilitation increased from habituation to change trials regardless of whether the change stimulus was presented in the same or in a different modality as the reflex-eliciting stimulus. These results are not consistent with modality-specific accounts of attentional startle modulation.

Expression of POU, Sox, and Pax genes in the brain ganglia of the tropical abalone Haliotis asinina

In gastropod mollusks, neuroendocrine cells in the anterior ganglia have been shown to regulate growth and reproduction. As a first step toward understanding the molecular mechanisms underlying the regulation of these physiological processes in the tropical abalone Haliotis asinina, ive have identified sets of POU, Sox, and Pax transcription factor genes that are expressed in these ganglia. Using highly degenerate oligonucleotide primers designed to anneal to conserved codons in each of these gene families, we have amplified by reverse transcriptase polymerase chain reaction 2 POU genes (HasPOU-III and HasPOU-IV), 2 Sox genes (HasSox-B and HasSox-C), and two Pax genes (HasPax-258 and HaxPax-6). Analyses with gene-specific primers indicated that the 6 genes are expressed in the cerebral and pleuropedal ganglia of both reproductively active and spent adults, in a number of sensory structures, and in a subset of other adult tissues.

Dual processes in recognition: Does a focus on measurement operations provide a sufficient foundation?

Current theoretical thinking about dual processes in recognition relies heavily on the measurement operations embodied within the process dissociation procedure. We critically evaluate the ability of this procedure to support this theoretical enterprise. We show that there are alternative processes that would produce a rough invariance in familiarity (a key prediction of the dual-processing approach) and that the process dissociation procedure does not have the power to differentiate between these alternative possibilities. We also show that attempts to relate parameters estimated by the process dissociation procedure to subjective reports (remember-know judgments) cannot differentiate between alternative dual-processing models and that there are problems with some of the historical evidence and with obtaining converging evidence. Our conclusion is that more specific theories incorporating ideas about representation and process are required.

An exploratory study of gendered differences in young tourists perception of danger within London

This paper studies young tourists' perception of danger within the urban holiday environment of London, England. The study of perceived danger is important not only in its own right, but also because of the influence it may have on use of leisure spaces and times. This research assesses gender and group composition differences in perception of danger, addressing the relatively neglected issues of men's perception and the relationship between the genders. For the purpose of this paper 'danger' was assessed by studying how safe, relaxed, vulnerable, threatened, and at risk people felt while in London. The study found a number of similarities and differences between the men and women studied, in terms of how they perceived danger and their group composition during the day and nigh-time. These results indicate that gender may not be the only influence on perception and behaviour, and that men and women should not be regarded as-homogenous cohorts. (C) 2001 Elsevier Science Ltd. All rights reserved.

Effects of temporal association on recognition memory

The influence of temporal association on the representation and recognition of objects was investigated. Observers were shown sequences of novel faces in which the identity of the face changed as the head rotated. As a result, observers showed a tendency to treat the views as if they were of the same person. Additional experiments revealed that this was only true if the training sequences depicted head rotations rather than jumbled views: in other words, the sequence had to be spatially as well as temporally smooth. Results suggest that we are continuously associating views of objects to support later recognition, and that we do so not only on the basis of the physical similarity, but also the correlated appearance in time of the objects.

Contingent attentional capture or delayed allocation of attention?

Under certain circumstances, external stimuli will elicit an involuntary shift of spatial attention, referred to as attentional capture. According to the contingent involuntary orienting account (Folk, Remington, & Johnston, 1992), capture is conditioned by top-down factors that set attention to respond involuntarily to stimulus properties relevant to one's behavioral goals. Evidence for this comes from spatial cuing studies showing that a spatial cuing effect is observed only when cues have goal-relevant properties. Here, we examine alternative, decision-level explanations of the spatial cuing effect that attribute evidence of capture to postpresentation delays in the voluntary allocation of attention, rather than to on-line involuntary shifts in direct response to the cue. In three spatial cuing experiments, delayed-allocation accounts were tested by examining whether items at the cued location were preferentially processed. The experiments provide evidence that costs and benefits in spatial cuing experiments do reflect the on-line capture of attention. The implications of these results for models of attentional control are discussed.

Psychometric evaluation of the Early/Late Preferences Scale

This paper examines the psychometric quality of the Early/Late Preferences Scale (PS) relative to that of the Composite Morningness Scale (CS). Questionnaires were completed by 670 undergraduate students aged 16-37 years (mean 22.5), of whom 64% were female. Both scales displayed satisfactory inter-item correlations and similar total mean scores to those reported previously, although the CS had higher variability. Principal axis factor analysis produced single-factor solutions for both scales, although loadings for Items 7 and 9 on the PS were low. Internal consistencies for both scales were good (PS=0.86, CS=0.90) with only a small improvement achieved by deleting Items 7 and 9 from the PS. Test-retest reliability over 11 weeks was good for both scales (PS=0.92, CS=0.89). Differences between morning, evening and intermediate groups in self-rated alertness at different times of day, and significant correlations with other indices of morning-evening orientation, provided evidence of validity for both scales. These results indicate that PS is psychometrically comparable with CS. In view of its simpler format and lower cultural specificity, PS may be considered a preferable measure for most applications.