On the loss of information in conditional maximum likelihood estimation of item parameters

In item response models of the Rasch type (Fischer & Molenaar, 1995), item parameters are often estimated by the conditional maximum likelihood (CML) method. This paper addresses the loss of information in CML estimation by using the information concept of F-information (Liang, 1983). This concept makes it possible to specify the conditions for no loss of information and to define a quantification of information loss. For the dichotomous Rasch model, the derivations will be given in detail to show the use of the F-information concept for making comparisons for different estimation methods. It is shown that by using CML for item parameter estimation, some information is almost always lost. But compared to JML (joint maximum likelihood) as well as to MML (marginal maximum likelihood) the loss is very small. The reported efficiency in the use of information of CML to JML and to MML in several comparisons is always larger than 93%, and in tests with a length of 20 items or more, larger than 99%.     

Born to adapt, but not in your dreams

The brain adapts to changes that take place in the body. Deprivation of input results in size reduction of cortical representations, whereas an increase in input results in an increase of representational space. Amputation forms one of the most dramatic disturbances of the integrity of the body. The brain adapts in many ways to this breakdown of the afferent–efferent equilibrium. However, almost all studies focus on the sensorimotor consequences. It is not known whether adaptation takes place also at other “levels” in the system. The present study addresses the question whether amputees dream about their intact body, as before the amputation, or about the body after the amputation and whether the dream content was a function of time since the amputation and type of amputation. The results show that the majority of the dreamers reported dreams about their intact body although the mean time that elapsed since the amputation was twelve years. There is no clear relation with the type of amputation. The results give modest evidence for the existence of a basic neural representation of the body that is, at least, partly genetically determined and by this relatively insensitive for changes in the sensory input.     

RECURRING THEMES IN THE DEBATE ABOUT EUTHANASIA AND ASSISTED SUICIDE

During the past four decades, the Netherlands played a leading role in the debate about euthanasia and assisted suicide. Despite the claim that other countries would soon follow the Dutch legalization of euthanasia, only Belgium and the American state of Oregon did. In many countries, intense discussions took place. This article discusses some major contributions to the discussion about euthanasia and assisted suicide as written by Nigel Biggar (2004) , Arthur J. Dyck (2002) , Neil M. Gorsuch (2006) , and John Keown (2002) . They share a concern that legalization will undermine a society's respect for the inviolability and sanctity of life. Moreover, the Report of the House of Lords Select Committee on the Assisted Dying for the Terminally Ill Bill (2005) is analyzed. All studies use ethical, theological, philosophical, and legal sources. All these documents include references to experiences from the Netherlands. In addition, two recent Dutch documents are analyzed which advocate further liberalization of the Dutch euthanasia practice, so as to include infants (Groningen Protocol, NVK 2005 ) and elderly people “suffering from life” (Dijkhuis Report, KNMG 2004 ).     

Selective reaching: evidence for multiple frames of reference

Students participated in 3 experiments investigating the use of environment- and action-centered reference frames in selective reaching. They pointed to a green target appearing either with or without a red distractor. Target-distractor distance was manipulated, and distractor interference (difference between distractor trials and no-distractor trials) was measured in reaction time, movement time, and movement endpoint. Target-distractor distance determined the dominant frame of reference. Small distances evoked an environment-centered framework that encoded targets within an external context. Large distances evoked an action-centered framework that encoded targets relative to the start position of the hand. Results support the hypothesis that the brain represents spatial information in multiple frames of reference, with the dominant frame of reference being dependent on the task demands.     

Identifying Children at Risk of Problematic Development: Latent Clusters Among Childhood Arrestees

The presence of clusters characterized by distinct profiles of individual, family and peer characteristics among childhood arrestees was investigated and cluster membership stability after 2 years was determined. Identification of such clusters in this heterogeneous at-risk group can extend insight into the presence and severity of children’s co-occurring problems and guide intervention and prevention efforts. Latent class analysis (LCA) was used to detect clusters among 308 childhood arrestees (mean age 10.7 years), based on dichotomous dynamic correlates of offending present at the time of first arrest. Correlates in the individual, peer and family domains were assessed at baseline and 2-year follow-up, using standardized instruments. This resulted in identification of a low problem group characterized by few problems across all domains (40.2 %), an externalizing intermediate problem group characterized by mainly externalizing problems on the individual and peer domains (39.4 %), and a pervasive high problem group characterized by numerous problems across all domains (20.4 %). Cluster membership was most stable for the low problem group (71.4 %), followed by the externalizing intermediate problem group (49.5 %). Transition was highest in the pervasive high problem group (63.0 %), with the majority of children progressing to the externalizing intermediate problem group. The identification of such distinct clusters among childhood arrestees, differing in the presence of co-occurring problems, stresses the importance of a first police arrest as an opportunity for early recognition of children in need of care. As problems present at the time of first arrest do not persist in every child, careful periodic monitoring is needed.     

The role of the degree of acquaintance with teachers on students’ interpersonal perceptions of their teacher

Some researchers suggest that the way a teacher is perceived during the first encounter with a classroom group resembles, and therefore is predictive of, later classroom processes as perceived by students. This study investigated the degree to which interpersonal ratings (i.e., control and affiliation), given by secondary school students to teachers unknown to them, are comparable to ratings given by students who are well acquainted with that teacher, by means of a quasi-experimental design. Ratings concerning a teacher students had not met before, based on a 5 min video vignette, were compared to ratings given by students who had been taught by the same teacher for at least a year (N $\,{=}\,$ 489). Students at no acquaintance perceived a teacher’s interpersonal traits in a similar way as students who were familiar with that teacher. It is concluded that students’ early interpersonal perceptions of a teacher largely resemble perceptions formed by students that know this teacher well.     

After the slippery slope: Dutch experiences on regulating active euthanasia

"When a country legalizes active euthanasia, it puts itself on a slippery slope from where it may well go further downward." If true, this is a forceful argument in the battle of those who try to prevent euthanasia from becoming legal. The force of any slippery slope argument, however, is by definition limited by its reference to future developments which cannot empirically be sustained. Experience in the Netherlands--where a law regulating active euthanasia was accepted in April 2001--may shed light on the strengths as well as the weaknesses of the slippery slope argument in the context of the euthanasia debate. This paper consists of three parts. First, it clarifies the Dutch legislation on euthanasia and explains the cultural context in which it originated. Second, it looks at the argument of the slippery slope. A logical and an empirical version are distinguished, and the latter, though philosophically less interesting, proves to be most relevant in the discussion on euthanasia. Thirdly, it addresses the question whether Dutch experiences in the process of legalizing euthanasia justify the fear of the slippery slope. The conclusion is that Dutch experiences justify some caution.