How to Assess a Model's Testability and Identifiability

Formal definitions are given of the following intuitive concepts: (a) A model is quantitatively testable if its predictions are highly precise and narrow. (b) A model is identifiable if the values of its parameters can be ascertained from empirical observations. (c) A model is redundant if the values of some parameters can be deduced from others or if the values of some observables can be deduced from others. Various rules of thumb for nonredundant models are examined. The Counting Rule states that a model is quantitatively testable if and only if it has fewer parameters than observables. This rule can be safely applied only to identifiable models. If a model is unidentifiable, one must apply a generalization of the Counting Rule known as the Jacobian Rule. This rule states that a model is quantitatively testable if and only if the maximum rank (i.e., the number of linearly independent columns) of its Jacobian matrix (i.e., the matrix of partial derivatives of the function that maps parameter values to the predicted values of observables) is smaller than the number of observables. The Identifiability Rule states that a model is identifiable if and only if the maximum rank of its Jacobian matrix equals the number of parameters. The conclusions provided by these rules are only presumptive. To reach definitive conclusions, additional analyses must be performed. To illustrate the foregoing, the quantitative testability and identifiability of linear models and of discrete-state models are analyzed. Copyright 2000 Academic Press.     

The sounds of dominance.

A study was conducted to determine the effects of vocal cues on judgements of dominance in an interpersonal influence context. Physical measures of human vocal cues and participant ratings of dominance were obtained from videotapes of actors delivering short influence messages. After controlling for linguistic and visual content of messages, results indicated that mean amplitude and amplitude standard deviation were positively associated with dominance judgments, whereas speech rate was negatively associated with dominance judgments. An unexpected interaction revealed that mean fundamental frequency (F₀) was positively associated with dominance judgments for male speakers but not significantly associated with dominance judgments for female speakers. F₀ standard deviation was not significantly associated with dominance judgments. Results support the conclusion that dominance judgments are inferred from multiple sources of information and that some vocal markers of dominance are more influential than others.     

Hypothalamo-Pituitary-Adrenocortical Regulation Following Lesions of the Central Nucleus of the Amygdala

Previous reports indicate that the central nucleus of the amygdala (CeA) stimulates adrenocorticotropin and corticosterone secretion, suggesting a role for this region in central hypothalamo-pituitary-adrenocortical (HPA) stress regulation. To evaluate this hypothesis, this study assessed the impact of CeA lesion on the response of hypophysiotrophic paraventricular nucleus (PVN) neurons to acute restraint and chronic unpredictable stress exposure. In contrast to previous reports, CeA lesions did not affect corticosterone or ACTH secretion induced by acute stress. Acute restraint increased PVN corticotropin releasing hormone (CRH) mRNA expression, increased the number of parvocellular PVN neurons expressing the co-secretagogue arginine vasopressin (AVP), and induced cFOS mRNA expression in the parvocellular PVN. However, there was no additional effect of CeA lesion on any measure of PVN activation. Chronic unpredictable stress exposure induced long-term activation of the HPA axis, noted by thymic involution, adrenal hypertrophy and increased PVN CRH mRNA expression. Stress-induced changes in thymus and adrenal weights were not affected by CeA lesion. Further, CeA lesion rats did not differ from controls in post-stress CRH mRNA expression. However, basal CRH mRNA expression was increased in the PVN of CeA rats, suggesting that the CeA plays a role in long-term inhibition of the PVN. The results of these studies are not consistent with the hypothesis that the CeA is necessary for stress-induced pituitary-adrenocortical activation. Rather, this region may play a stressor-specific modulatory role in regulation of HPA function.     

Emotional response to abortion: a critical review of the literature

Anti-abortion groups in the US cite the existence of a post-abortion syndrome--a sense of loss, emptiness, and grief similar to that reported by trauma survivors. Although research on the longterm effects of induced abortion is marred by methodological errors, most studies have found no adverse psychological sequelae; rather, there appears to be a sense of relief and opportunity for personal growth. Nevertheless, there is a small group of women who do experience emotional distress after abortion and it is important to identify the demographic, social, and psychological factors that place women at risk of such a reaction. In terms of demographic factors, young age (adolescence), low or nulliparity, 2nd-trimester procedures, and Catholicism have been characteristics of women who suffered post-abortion depression. Of the social variables that have been examined, a lack of support from significant others (parents or partner) has been linked in some studies to emotional distress after abortion. A relatively consistent finding is that women who feel coerced to abort or are ambivalent about their decision at the time of the procedure are most likely to experience regret, depression, and anger. Women whose coping style involves avoiding responsibility are also prone to post-abortion distress. As noted, the literature does not support the contention that abortion causes longterm trauma. On the other hand, given the fact that 1.5 million abortions take place each year in the US, the existence of some post-abortion distress in even as small percentage of acceptors is enough to indicate a need for pre- and post-abortion counseling to help women determine the meaning of the experience and own their decisions.     

Persuasion and the structure of affect.

Participants viewed eight PSAs, providing data on their cognitive and emotional responses to each, as well as judgments of the perceived effectiveness of the messages. They also responded to Carver and White's (1994) BIS/BAS scales designed to measure individual differences in the behavioral inhibition and behavioral activation systems. Consistent with dual‐systems theories of affect, the BIS scales predicted arousal of negative emotions, while BAS was associated with the elicitation of positive emotions. However, when predicting perceived message effectiveness, the positive affects showed variation in the sign and magnitude of the coefficients, as did the negative affects. This latter finding supports a discrete‐emotions perspective. Knowledge that the two affect structures are appropriate to different conceptual domains (i.e., elicitation vs. effect) should enable researchers to formulate more precise questions regarding the role of affect in persuasion.     

The Washington University Sentence Complete Test: are the two halves alternate forms? Are the female and male forms comparable?

Evidence from 85 adult medical outpatients supported psychometric comparability of the 2 halves of the Washington University Sentence Completion Test (SCT) Form 81 and of the female and male forms of the SCT. There was slightly stronger internal consistency for the first versus the second half of the SCT. Each half correlated highly with the ogive total protocol rating and 36-item-sum rating. Intercorrelations of the 2 halves with external measures also suggested essentially equivalent relations. For the 30 identical items across gender, the median correlation between individual item ratings with the item-sum ratings was nearly equal for women and men. When the 6 nonidentical items were considered with the identical items, the median item-total correlation was slightly higher for men (45) than women (41). This difference was accounted for by the slightly larger variability in the mate subsample. Practically speaking, the 2 halves and the female and male forms may be used with minimal concern regarding psychometric comparability in similar medical outpatient settings.     

The association between patterns of family functioning and ego development of the juvenile offender.

The present study revealed an association between the family configurations of cohesion and adaptability and juvenile offenders' level of ego development. This association was explained by four post hoc comparisons which revealed that functional perspectives of family cohesion and adaptability by the juvenile offender and one or both parents were associated with higher levels of ego development. Lower levels of ego development were associated with (a) shared dysfunctional perspectives of the family dimensions by the juvenile offender and both parents, and (b) a functional perspective of the family dimensions by the juvenile offender which was not shared by either parent. These results were based on 61 nonchronic juvenile offenders and their parents who were assessed by the Family Adaptability and Cohesion Evaluation Scales II. The offenders' level of ego development was assessed by the Washington University Sentence Completion Test.     

Domain specific aspects of locus of control: Implications for modifying locus of control orientation

An examination was made to see if locus of control orientation with respect to intellectual achievement could be changed and to determine whether the change generalized to other types of situations. Goal-setting conferences were employed to improve LOC orientation for academic achievement situations among junior high school students. Significant differences were observed between the goal-setting conference group, the conference only group, and the control group on three measures of LOC orientation pertaining to academic situations: IAR⁺ and IAR- scores from the Intellectual Achievement Responsibility Questionnaire, plus the IA subscale of LOCITAD. No significant differences were recorded on the SA (LOC orientation for social achievement situations) and the PA (LOC orientation for physical achievement situations) of LOCITAD. High correlations were observed between Intellectual Achievement Responsibility scores and scores on the IA subscale of LOCITAD. More moderate correlations were observed between IAR scores and the other LOCITAD subscales. Results were interpreted as supporting domain-specific aspects of LOC. Results implied that educators can design programs to modify LOC orientation with less fear that a more internal orientation for academic situations will lead to maladaptive responses in other types of situations. Results also support the development of more precise measures of LOC.     

Expansion of Genetic Services Utilizing a General Genetic Counseling Clinic

We established a general genetic counseling clinic (GCC) to help reduce long wait times for new patient appointments and to enhance services for a subset of patients. Genetic counselors, who are licensed in Tennessee, were the primary providers and MD geneticists served as medical advisors. This article describes the clinic referral sources, reasons for referral and patient dispositions following their GCC visit(s). We obtained patients by triaging referrals made to our medical genetics division. Over 24 months, our GCC provided timely visits for 321 patients, allowing the MD geneticists to focus on patients needing a clinical exam and/or complex medical management. Following their GCC visit(s), over 80 % of patients did not need additional appointments with an MD geneticist. The GCC allowed the genetic counselor to spend more time with patients than is possible in our traditional medical genetics clinic. Patient satisfaction surveys (n?=?30) were very positive overall concerning the care provided. Added benefits for the genetic counselors were increased professional responsibility, autonomy and visibility as health care providers. We conclude that genetic counselors are accepted as health care providers by patients and referring providers for a subset of clinical genetics cases. A GCC can expand genetic services, complement more traditional genetic clinic models and utilize the strengths of the genetic counselor health care provider.