A measure of effect size for experimental designs with heterogeneous variances

A recent trend in the psychological literature has been to include measures of effect size when reporting probability values. The several measures of effect size associated with the Student t test for two independent samples are appropriate only when the variances are homogeneous. In this paper, commonly used measures of effect size are considered and compared, using four data sets. A chance-corrected measure of effect size is provided for two or more treatment groups characterized by either homogeneous or heterogeneous variances.     

A positive emotional bias in confabulatory false beliefs about place

Some neurological patients with medial frontal lesions exhibit striking confabulations. Most accounts of the cause of confabulations are cognitive, though the literature has produced anecdotal suggestions that confabulations may not be emotionally neutral, having a ('wish-fulfilment') bias that shapes the patient's perception of reality in a more affectively positive direction. The present study reviewed every case (N = 16) of false beliefs about place reported in the neuroscientific literature from 1980 to 2000, with blind raters evaluating the 'pleasantness' of the patient's actual and confabulated locations. In each case the confabulated location was evaluated as more pleasant. This striking finding supports the claim that there may be a systematic affective bias in the false beliefs held by neurological patients with confabulation.     

Inactivation of the anterior cingulate cortex impairs extinction of rabbit jaw movement conditioning and prevents extinction-related inhibition of hippocampal activity

Although past research has highlighted the involvement of limbic structures such as the anterior cingulate cortex (ACC) and hippocampus in learning, few have addressed the nature of their interaction. The current study of rabbit jaw movement conditioning used a combination of reversible lesions and electrophysiology to examine the involvement of the hippocampus and the ACC during acquisition, performance, and extinction. We found that microinfusions of procaine into the ACC did not significantly alter the rate of behavioral learning or the amplitude of hippocampal conditioned unit responses, but that they disrupted the rhythmic periodicity of conditioned jaw movements. During extinction, whereas controls showed a rapid decline in behavioral CRs and active inhibition of hippocampal unit responses, ACC lesioned rabbits showed a persistence of conditioning-related hippocampal activity and behavioral responding. The results show that the ACC can be important for adaptive suppression of conditioned behavior and suggest a crucial physiological modulation of hippocampus by ACC during extinction.     

Multiple-family group treatment of outpatients with schizophrenia: impact on service utilization

The impact of multiple-family group treatment (MFGT) on outpatient and inpatient mental health service utilization of 97 persons with schizophrenia was investigated. Participants were randomly assigned to standard care (n = 44) or standard care plus MFGT (n = 53). Service use for a year prior to randomization, the 2-year study period, and a 1-year follow-up were examined. Relative to standard care participants, the MFGT group had reduced community hospitalization during year 1 of the intervention and reduced state hospitalization at follow-up. During the intervention period, MFGT participants demonstrated a significant increase in outpatient utilization as a direct consequence of the intervention. However, when service use was summed across 3 years post-randomization, no group differences were observed. Results suggest that implementation of MFGT in a community mental health setting reduces inpatient service at specific time periods, without significantly increasing outpatient service utilization. These findings add to other outcomes from this study that demonstrate decreased psychiatric symptoms and caregiver distress.     

Comprehending narratives containing flashbacks: evidence for temporally organized representations

This study investigated the representations that readers construct for narratives describing a sequence of events. Participants read narratives describing 4 successive events in chronological order (Event 1, Event 2, Event 3, Event 4 [E1, E2, E3, E4] Experiment 1) or in nonchronological order with E1 being mentioned in a flashback (E2, E3, E1, E4; Experiments 2-4). The information about the duration of E2 was manipulated, and the mental accessibility of E1 was tested at the end of a passage. All 4 experiments showed that E1 was less accessible if the text implied that it occurred a relatively long time ago in the described world compared with when it occurred a shorter time ago. This result suggests that readers construct a temporally organized representation even if the text structure does not suggest such an organization.     

Multivariate multiple regression analyses: a permutation method for linear models

A multivariate extension of a univariate procedure for the analysis of experimental designs is presented. A Euclidean-distance permutation procedure is used to evaluate multivariate residuals obtained from a regression algorithm, also based on Euclidean distances. Applications include various completely randomized and randomized block experimental designs such as one-way, Latin square, factorial, nested, and split-plot designs, with and without covariates. Unlike parametric procedures, the only required assumption is the randomization of subjects to treatments.     

Screening for feigned psychiatric symptoms in a forensic sample by using the MMPI-2 and the structured inventory of malingered symptomatology

Fifty-five men undergoing pretrial psychological evaluations for competency to stand trial or criminal responsibility in the federal justice system were administered the Structured Interview of Reported Symptoms (SIRS), the Minnesota Multiphasic Personality Inventory--2 (MMPI-2), and the Structured Inventory of Malingered Symptomatology (SIMS). On the basis of results from the SIRS, 31 were classified as honest responders and 24 as feigning. Significant differences between the 2 groups were found on all SIMS scales as well as on all tested MMPI-2 fake bad validity scales. The SIMS total score and the MMPI-2 Backpage Infrequency (Fb) scale had relatively high negative predictive power (100% and 92%, respectively). On the basis of this clinically relevant methodology, both tests have potential usefulness as screens for malingering.     

Auditory memory and the irrelevant sound effect: Further evidence for changing-state disruption

Four experiments investigate the hypothesis that irrelevant sound interferes with serial recall of auditory items in the same fashion as with visually presented items. In Experiment 1 an acoustically changing sequence of 30 irrelevant utterances was more disruptive than 30 repetitions of the same utterance (the changing-state effect; Jones, Madden, & Miles, 1992) whether the to-be-remembered items were visually or auditorily presented. Experiment 2 showed that two different utterances spoken once (a heterogeneous compound suffix; LeCompte & Watkins, 1995) produced less disruption to serial recall than 15 repetitions of the same sequence. Disruption thus depends on the number of sounds in the irrelevant sequence. In Experiments 3a and 3b the number of different sounds, the "token-set" size (Tremblay & Jones, 1998), in an irrelevant sequence also influenced the magnitude of disruption in both irrelevant sound and compound suffix conditions. The results support the view that the disruption of memory for auditory items, like memory for visually presented items, is dependent on the number of different irrelevant sounds presented and the size of the set from which these sounds are taken. Theoretical implications are discussed.     

The nonconscious influence of religious symbols in motivated performance situations

Anthropological, sociological, and psychological theories suggest that religious symbols should influence motivational processes during performance of goal-relevant tasks. In two experiments, positive and negative religious (Christian) symbols were presented outside of participants' conscious awareness. These symbols influenced cardiovascular responses consistent with challenge and threat states during a subsequent speech task, particularly when the speech topic concerned participants' mortality, and only for Christian participants; similar images lacking Christian meaning were not influential. Results suggested that these effects were due to the learned meaning of the symbols and point to the importance of religion as a coping resource.