Latent curve analysis

As a method for representing development, latent trait theory is presented in terms of a statistical model containing individual parameters and a structure on both the first and second moments of the random variables reflecting growth. Maximum likelihood parameter estimates and associated asymptotic tests follow directly. These procedures may be viewed as an alternative to standard repeated measures ANOVA and to first-order auto-regressive methods. As formulated, the model encompasses cohort sequential designs and allow for period or practice effects. A numerical illustration using data initially collected by Nesselroade and Baltes is presented.The authors wish to thank John Nesselroade for providing us the data for our illustration and Karen Paul and Connie Tilse for assisting in the data analysis. This research was supported by a grant (No. AG03164) from the National Institute on Aging to the senior author.     

Change and stability in adult intellectual functioning assessed by Wechsler item responses

Change in adult intellectual performance was assessed with longitudinal data from the Intergenerational Studies at the Institute of Human Development. Wechsler Intelligence data from two age cohorts spanning ages 18 to 61 were analyzed at the subtest and item level. Hotelling T2 analyses on sets of equivalent items from Wechsler subtests were studied to determine if change in response occurred between pairwise combinations of occasions of test administrations. We used Bowker's test to analyze data at the item level to determine the direction of change in performance. Consistent improvement in performance occurred between the ages of 18-40 and 18-54. Between the ages of 40 and 61, results showed mostly improved performance on the Information, Comprehension, and Vocabulary subtests, mixed change on the Picture Completion subtest, and decline on the Digit Symbol and Block Design subtests. The pattern of mixed change on the Picture Completion subtest indicated improvement on the easy items and decline on the difficult items. Decline in performance on the Block Design test occurred only for the most difficult items.     

A Brain of Her Own: A Neural Correlate of Song Assessment in a Female Songbird

The song control region in the avian forebrain is a series of discrete, interconnected nuclei mediating song learning and production. It has been studied in males or in species where both sexes sing. Little is known about the neural correlates of song perception in nonsinging females, often the intended recipients of song. We studied cowbirds (Molothrus ater), a species in which only males sing but in which females discriminate between males on the basis of song. We focused on nucleus lMAN because it has been implicated in early song acquisition, a stage relevant to both sexes to choose among competing acoustic models. We found that volume of lMAN was monomorphic in cowbirds. Moreover, the volume and neuronal number of female lMAN were positively correlated with selectivity of copulatory responding. The results provide strong evidence of nonsinging female's use of “song” control nuclei for song perception without the possibility of song production.     

Other mothers: toward an ethic of postmaternal practice

This essay attempts a deliberately perverse interpretation of die new reproductive practices (e.g., contract pregnancy, in vitro fertilization, etc.) in an effort to rethink maternal subjectivity and the bodies that might accompany it.     

Work and nonwork stressors,negative affective states,and pain complaints among firefighters and paramedics

Prior research has suggested that occupational stressors may contribute to the etiology, progression, and chronicity of pain problems in workers. This study used anonymous survey methods to assess the prevalence and frequency of self-reported pain symptoms and their relationships to demographic variables, sources of occupational stressors, nonwork stressors and affective distress in a large sample (N2000) of employed career public sector firefighters and paramedics. The findings were consistent with those of previous studies of high strain workers. More than 95% of the firefighter/paramedic sample reported at least one pain complaint (using a 1 week assessment time frame). A hierarchical multiple regression analysis entering demographic, occupational, and nonwork stressors, as well as measures of negative affective states targeting total pain scores, yielded significant relationships. Five occupational stressors were associated with respondent pain complaints. The results also suggest that negative affective states mediated the relationships between work and nonwork variables, and pain complaint outcomes. The implications of these findings for the development of preventive interventions for firefighters and paramedics as well as other emergency service workers are considered.     

The components of latency of response in two models for auditory detection with deadlines

Two models are described for the case of auditory detection with response time deadlines. These are the “timing” model, modified from Luce and Green (1972), and the “interval of uncertainty” (IU) model, modified from the “counting” model of McGill (1967). The two models are expressed in the form of additive component latencies, including a component which varies inversely with probability of response and a component for a longer response on the “nondeadline” response condition. An experiment is described, incorporating deadlines on both s and n trials separately, and the additive component latencies of the models are calculated. The “interval of uncertainty” model is seen to represent the data better than the “timing” model, even though different versions of the latter model are considered. Parameters are then fitted to give a representation of the IU model. The data from one subject of another study not employing deadlines can also be fitted to the model, and an interesting problem then arises concerning the exact locus of the speed-accuracy tradeoff. It is concluded that the IU model needs extending if it is to describe the data without the use of a component of latency which varies inversely with response probability.     

The latencies of correct and incorrect responses in discrimination and detection tasks: Their interpretation in terms of a model based on simple counting

A model for two-choice discrimination based on a process of simple counting is described, and two experiments are performed to test the predictions of the model concerning the graph of latency as a function of response proportion. Two main forms of this graph are identified and predicted to arise in different circumstances. The experimental results support the model, and its possible extension to other psychophysical situations, especially signal detection, are then discussed. It is compared with a model derived directly from the detection situation, and the usefulness of testing these models is pointed out.     

Response latencies in the yes/no detection task: An assessment of two basic models

Two general forms of model for response latency in the yes no signal detection task are described and their predictions examined in the light of experimental data. One model supposes a latency function along the detection axis and the other supposes that a count is made of multiple observation, Experiment I looks at the auditory detection situation with short observation interval, but the results are generally equixocal, although the latency function model gives a simpler interpretation Other results are then discussed, particularly those of Gescheider et al (1969). and it is concluded that an attempt must be made to replicate the results of Carterette et al (1965) for the extended observation interval detection experiment. This is achieved in Experiment II. and the obtained order of mean latencies is then examined in terms of the models The counting model appears by far the more suitable for this situation.