Biomedical subjects

J V Podd

Publications and source records attributed to J V Podd.

6 recordsLinked to original sources

PubMed1999

Stability of driving fear acquisition pathways over one year.

The present study was conducted in response to increasing concerns about the potential unreliability of retrospective accounts in assessing the origins of fears and phobias. Some investigators [e.g. Menzies, R.G., & Clarke, J.C. (1993). The etiology of fear of heights and its relationship to severity and individual response patterns. Behaviour Research and Therapy, 31, 355-365; Kirkby, K.C., Menzies, R.G., Daniels, B.A., & Smith, K.L. (1995). Aetiology of spider phobia: Classificatory differences between two origins instruments. Behaviour Research and Therapy, 33, 955-958; King, N.J., Gullone, E., & Ollendick, T.H. (1998). Etiology of childhood phobias: current status of Rachman's three pathways theory. Behaviour Research and Therapy, 36, 297-309.] have questioned the reliability of retrospective reports at a single assessment point, although the test-retest reliability of such accounts has yet to be examined. The aim of the present study was to conduct a one-year follow-up of the subclinical driving-fearful sample studied by Taylor and Deane [Taylor, J. E., & Deane, F. P. (1999). Acquisition and severity of driving-related fears. Behaviour Research and Therapy, 37, 435-449.] to primarily investigate, the stability of fear onset ascriptions and fear severity over time. 85 respondents completed a questionnaire which assessed fear origins, anxiety response patterns, and additional fear-relevant events occurring over the year. The results suggest that retrospective accounts of fear onset may be quite unstable over time, although this instability does not clearly appear to be related to intervening events, and limitations of the study make these results inconclusive. Fear-relevant negative thinking worsened over time, while physiological reactions and general anxiety remained relatively stable. The theoretical, methodological and clinical implications of the findings are discussed, along with suggestions for future research.

Adult↗

PubMed1998

Influence of extremely low frequency magnetic fields on chromosomes and the mitotic cycle in Vicia faba L., the broad bean.

Vicia faba seedlings were subjected to one of the following magnetic fields continuously for 3 days: 0 Hz (DC) at 5 mT, 50 Hz at 1.5 mT, 60 Hz at 1.5 mT, and 75 Hz at 1.5 mT. The lengths of all the phases of mitosis differed from the controls in all treatments using alternating magnetic fields and for prophase and metaphase in the DC condition. In particular, all treatments increased the length of prophase significantly in meristematic root-tip cells compared with the controls. The implications of these results for chromosome coiling are discussed. The length of prophase, however, did not vary significantly between any of the treatments. Furthermore, none of the exposed seedlings had a greater frequency of chromosome breakages above that of the control plants.

Cell Cycle↗

PubMed1996

Acute effects of 50 Hz magnetic field exposure on human visual task and cardiovascular performance.

One hundred subjects, males and females with ages ranging between 18 and 48 years, were studied under both field-exposed and sham-exposed conditions. A 50 Hz, 100 mu T magnetic field (MF) was used. To examine the effect of field exposure on performance, a two-alternative, forced-choice, duration-discrimination task with three levels of difficulty was used. The subject's task was to decide which of two sequentially presented light flashes had the longer duration. The standard duration was 50 ms, and the alternative durations were 65, 100, or 125 ms. Both reaction time and percentage of correct responses were recorded for each subject. MF and sham exposure were for 9 min each. Blood pressure and heart rate were also measured before and following MF exposure and sham-exposure trials. The study was performed double blind, with the exposure order counterbalanced. Compared to sham exposure, MF exposure significantly decreased reaction time on the hardest level of the performance task. MF exposure did not reliably affect percentage correct or cardiovascular performance. It was demonstrated that a relatively high level of statistical power was the basis for the observed MF effect, and the need to pay closer attention to power levels in future research is discussed.

Adolescent↗

PubMed1996

Human performance and physiology: a statistical power analysis of ELF electromagnetic field research.

Research examining the effects of electromagnetic fields (EMFs) on human performance and physiology has produced inconsistent results; this might be attributable to low statistical power. Statistical power refers to the probability of obtaining a statistically significant result, given the fact that a real effect exists. The results of a survey of published investigations of the effects of EMFs on human performance and physiology show that statistical power levels are very low, ranging from a mean of .08 for small effect sizes to .46 for large effect sizes. Implications of these findings for the interpretation of results are discussed along with suggestions for increasing statistical power.

Behavior↗

PubMed1995

Do ELF magnetic fields affect human reaction time?

Two double-blind studies were run in an attempt to confirm the finding that a 0.2 Hz magnetic field affects simple reaction time (RT) in humans, whereas a 0.1 Hz field does not. In the first experiment, 12 volunteer subjects were exposed to a continuous 0.2 Hz, 0.1 Hz, or sham field in a fully counterbalanced, within-subjects design. Subjects were run singly for one condition each day over 3 consecutive days with a field strength of 1.1 mT and a daily exposure duration of 5 min. Neither magnetic field had any effect on RT at any time during the exposure. One condition of a second study, using a new group of 24 volunteer subjects, also failed to find any field effects at 0.2 Hz. Additionally, the second study failed to show any effects when the frequency, flux density, and field orientation were set according to parametric resonance theory. It is suggested that, although ELF magnetic field effects on human behaviour may be elusive, future research can improve detection rates by paying greater attention to reducing error variance and increasing statistical power.

Adult↗

PubMedDate not supplied

Determining the focus of driving fears.

Fear of driving has been recognized as a complex diagnostic entity. Studies on flying phobia have drawn similar conclusions, although increasing clarity has been gained through research that indicates that there may be subtypes of flying phobia based on the focus of fear. However, it is unclear if similar subtypes exist for fear of driving. The aim of the present study was to conduct a preliminary investigation of driving fear subtypes and to clarify further whether there were differences between driving-fearful respondents who had been in a motor vehicle accident (MVA) and those who had not. Eighty-five driving-fearful, media-recruited respondents completed a questionnaire that assessed anxiety, avoidance, and concerns related to their driving fears. The sample had high expectations of negative events while driving. There were no significant differences between those who had experienced an MVA and those who had not on various measures of fear severity. Cluster analysis revealed two main foci of fear, one characterized by danger expectancies and the other based on anxiety expectancies and unpleasant driving situations. This emphasizes the importance of assessing both internal and external foci of fear. Although this finding is consistent with the results obtained for flying phobia, more research is required to replicate and extend these results and to develop and evaluate differential treatment programs.

Accidents, Traffic↗