Using a Gaussian Graphical Model to Explore Relationships Between Items and Variables in Environmental Psychology Research

Exploratory analyses are an important first step in psychological research, particularly in problem-based research where various variables are often included from multiple theoretical perspectives not studied together in combination before. Notably, exploratory analyses aim to give first insights into how items and variables included in a study relate to each other. Typically, exploratory analyses involve computing bivariate correlations between items and variables and presenting them in a table. While this is suitable for relatively small data sets, such tables can easily become overwhelming when datasets contain a broad set of variables from multiple theories. We propose the Gaussian graphical model as a novel exploratory analyses tool and present a systematic roadmap to apply this model to explore relationships between items and variables in environmental psychology research. We demonstrate the use and value of the Gaussian graphical model to study relationships between a broad set of items and variables that are expected to explain the effectiveness of community energy initiatives in promoting sustainable energy behaviors.

Computational nature of human adaptive control during learning of reaching movements in force fields

Learning to make reaching movements in force fields was used as a paradigm to explore the system architecture of the biological adaptive controller. We compared the performance of a number of candidate control systems that acted on a model of the neuromuscular system of the human arm and asked how well the dynamics of the candidate system compared with the movement characteristics of 16 subjects. We found that control via a supra-spinal system that utilized an adaptive inverse model resulted in dynamics that were similar to that observed in our subjects, but lacked essential characteristics. These characteristics pointed to a different architecture where descending commands were influenced by an adaptive forward model. However, we found that control via a forward model alone also resulted in dynamics that did not match the behavior of the human arm. We considered a third control architecture where a forward model was used in conjunction with an inverse model and found that the resulting dynamics were remarkably similar to that observed in the experimental data. The essential property of this control architecture was that it predicted a complex pattern of near-discontinuities in hand trajectory in the novel force field. A nearly identical pattern was observed in our subjects, suggesting that generation of descending motor commands was likely through a control system architecture that included both adaptive forward and inverse models. We found that as subjects learned to make reaching movements, adaptation rates for the forward and inverse models could be independently estimated and the resulting changes in performance of subjects from movement to movement could be accurately accounted for. Results suggested that the adaptation of the forward model played a dominant role in the motor learning of subjects. After a period of consolidation, the rates of adaptation in the internal models were significantly larger than those observed before the memory had consolidated. This suggested that consolidation of motor memory coincided with freeing of certain computational resources for subsequent learning.

Rising trend in the prevalence of HIV infection among blood donors

The prevalence of HIV infection among blood donors was analysed, for the five year period from April 1988 to March 1993. All donors were patients' relatives or volunteers; no paid/commercial donors were accepted. Each year between 14,084 and 15,544 donor blood samples were screened by ELISA and those found reactive were tested by Western blot. Western blot positive samples were considered to be infected with HIV. The prevalence rates were 1.5 per 1000 (1988-89), 1.1 per 1000 (1989-90 and 1990-91) 1.9 per 1000 (1991-92) and 3.1 per 1000 (1992-93). When the mean prevalence rate over the first three years [1.3 per 1000 (1988-89 to 1990-91)] was compared to the prevalence in 1991-92 (1.9/1000), increase was statistically significant (P < 0.05). The prevalence rate in 1992-93 (3/1000) was significantly higher than that of the previous year (P < 0.01). These data suggest that the prevalence of HIV infection in blood donors is increasing and this could be a reflection of the rising prevalence of HIV infection in the general population.

Prevalence of HIV infection in pregnant women in Vellore region

All pregnant women attending the antenatal clinic of a large hospital in Vellore, India (Christian Medical College Hospital) were screened for HIV infection between October 1987 and June 1992. A total of 36,953 blood samples were thus screened and 20 infected women were identified. Among these 18 women had acquired HIV infection from their husbands, who were also detected to be HIV infected. While these 18 women were monogamous, all the husbands had multiple sex partners. Two of the 20 women in this series were commercial sex workers. Among the 20, 17 (85%) women belonged to low socio-economic status, while three were from well-to-do families, with the husbands being businessmen or teachers. As the overall prevalence (0.054%) of HIV infection among pregnant women was relatively high and equal to or higher than many States in the USA and in areas outside London in the UK, the authors recommend that strict universal precautions be instituted in all obstetric practice in India.