Prediction of university students' academic achievement by linear and logistic models

University students' academic achievement measured by means of academic progress is modeled through linear and logistic regression, employing prior achievement and demographic factors as predictors. The main aim of the present paper is to compare results yielded by both statistical procedures, in order to identify the most suitable approach in terms of goodness of fit and predictive power. Grades awarded in basic scientific courses and demographic variables were entered into the models at the first step. Two hypotheses are proposed: (a) Grades in basic courses as well as demographic factors are directly related to academic progress, and (b) Logistic regression is more appropriate than linear regression due to its higher predictive power. Results partially confirm the first prediction, as grades are positively related to progress. However, not all demographic factors considered proved to be good predictors. With regard to the second hypothesis, logistic regression was shown to be a better approach than linear regression, yielding more stable estimates with regard to the presence of ill-fitting patterns.     

Maternal anxiety and depression and development of prematurely born infants in the first year of life

The purpose of this study was: (a) to assess and to compare anxiety and depression symptoms in mothers of preterm neonates during hospitalization in the Neonatal Intensive Care Unit, after discharge, and at the end of the infants' first year of life; and (b) to assess the child's development at 12 months of chronological corrected age (CCA). Thirty-six mothers, with no psychiatric antecedents assessed with the SCID-NP, were evaluated by STAI and BDI. The infants were assessed with Bayley-II Scales. There was a significant decrease in clinical symptoms of state-anxiety in mothers (p = .008), comparing the period during hospitalization and after discharge of the infants. Clinical symptoms of anxiety and depression were observed in 20% of the mothers at the end of the infants' first year of age. The majority of the infants exhibited normal development on Bayley-II at 12 months CCA; however, 25% of the infants displayed cognitive problems and 40% motor problems. The mothers' anxiety and depression symptoms decreased at the end of the first year of life of the pre-term infants and the children showed predominately normal development at this phase.     

Maternal concepts and expectations regarding a preterm infant

The objective of the present study was: (a) to identify the concerns, verbally expressed, of 50 mothers regarding their preterm infants (PT) and then compare their verbal expression with those of 25 mothers of full-term infants (FT); and (b) to correlate the mothers' verbal expressions with maternal and infant variables. The following instruments were used to compose and characterize the sample: Structure Clinical Interview for DSM III-R Non-Patient (SCID/NP), State-Trait Anxiety Inventory (STAI), Beck Depression Inventory (BDI), and medical charts. Results showed that there was no difference between groups in term of mothers' expectations and conceptualizations; both groups exhibited predominantly positive expectations and concepts. In comparison with FT mothers, PT mothers verbally expressed more feelings and reactions predominantly negative or conflicting in relation to infant birth. Higher levels of maternal anxiety and depression in the PT Group were correlated with more verbal expressions about negative or conflicting emotions. In addition, lower birth weight, higher neonatal risk and longer length of stay in intensive care nursery of the infants were related with more negative or conflicting concepts by the mothers.     

A comparison of the peers method and traditional methodologies, and risk behaviors in studies of the prevalence of drug consumption in a population of female, Chilean students

The present study investigates drug consumption and risk behaviors among female students between 8th and 12th grade in two communities in the city of Santiago, Chile. Based on studies of university populations, we hypothesize that the students' reports of their consumption of licit drugs will tend to be consistent with their actual use of said drugs using two methods to investigate consumption, while their consumption of illicit drugs will be susceptible, and will tend to be under-reported when evaluated through traditional self-report measures. In order to compare the two methods, a cross-sectional study was designed that would compare reported drug consumption, first using the peers method, and then by means of traditional self-report in a group of 350 students. The results show that women's reports of licit drug consumption converge using the two methods, while as earlier suggested, women's illicit drug consumption was found to be under-reported when traditional methodologies were used.     

Structure and conventions

Wayne Davis’s Meaning, Expression and Thought argues that linguistic meaning is conventional use to express ideas. An obvious problem with this proposal is that complex expressions that have never been used are nonetheless meaningful. In response to this concern, Davis associates conventions of use not only with linguistic expressions but also with the modes in which such expressions can combine into larger expressions. I argue that such constructive conventions are in conflict with the principle of compositionality (as it is usually understood) and that (at least in the cases Davis considers) they are unnecessary for semantic explanations.

On the Relationships between Sum Score Based Estimation and Joint Maximum Likelihood Estimation

This paper analyzes the sum score based (SSB) formulation of the Rasch model, where items and sum scores of persons are considered as factors in a logit model. After reviewing the evolution leading to the equality between their maximum likelihood estimates, the SSB model is then discussed from the point of view of pseudo-likelihood and of misspecified models. This is then employed to provide new insights into the origin of the known inconsistency of the difficulty parameter estimates in the Rasch model. The main results consist of exact relationships between the estimated standard errors for both models; and, for the ability parameters, an upper bound for the estimated standard errors of the Rasch model in terms of those for the SSB model, which are more easily available. The authors acknowledge partial financial support from the FONDECYT Project No. 1060722 from the Chilean Government, and the BIL05/03 grant to P. De Boeck, E. Lesaffre and G. Molenberghs (Flanders) for a collaboration with G. del Pino, E. San Martín, F. Quintana and J. Manzi (Chile).     

Neophilia in domestic dogs (Canis familiaris) and its implication for studies of dog cognition

This study examined novel-object preference in dogs. In a free choice test 17 dogs were presented with a novel toy in a line up with two familiar toys. The unfamiliar object was chosen first in 38 out 50 tests suggesting a strong preference for novel over familiar items. Neophilia may be an adaptive trait for domestic dogs that has helped their adaptation towards man.     

Female degus (Octodon degus) monitor their environment while foraging socially

Vigilance or scanning involves interruptions in foraging behavior when individuals lift their heads and conduct visual monitoring of the environment. Theoretical considerations assume that foraging with the "head down", and scanning ("head up") are mutually exclusive activities, such that foraging precludes vigilance. We tested this generalization in a socially foraging, small mammal model, the diurnal Chilean degu (Octodon degus). We studied spontaneous bouts of scanning of captive degus when foraging in pairs of female sibs and non-sibs. We examined the extent to which foraging (head down postures) and scanning (head up postures) were mutually exclusive in subjects exposed to none, partial, and complete lateral visual obstruction of their partners. In addition, we monitored the orientation of their bodies to examine the target of attention while foraging and scanning. Lastly, we examined the temporal occurrence of scanning events to assess the extent of scanning coordination, and whether this coordination is kin-biased. Visual obstruction had a significant influence on degu vigilance. Focal degus increased their quadrupedal and semi-erect scanning when foraging under a partially obstructed view of their partners. Degus oriented their bodies toward partners when foraging and scanning. Despite this, degus did not coordinate scanning bouts; instead, they scanned independently from one another. Relatedness among cage mates did not influence any aspect of degu behavior. Contrary to theoretical expectations, these results indicate that foraging and vigilance are not mutually exclusive, and that kinship per se does not influence scanning behavior and coordination.