Multilevel Mixture Factor Models

Factor analysis is a statistical method for describing the associations among sets of observed variables in terms of a small number of underlying continuous latent variables. Various authors have proposed multilevel extensions of the factor model for the analysis of data sets with a hierarchical structure. These Multilevel Factor Models (MFMs) have in common that—as in multilevel regression analysis—variation at the higher level is modeled using continuous random effects. In this article, we present an alternative multilevel extension of factor analysis which we call the Multilevel Mixture Factor Model (MMFM). It is based on the assumption that higher level units belong to latent classes that differ in terms of the parameters of the factor model specified for the lower level units. We demonstrate the added value of MMFM compared with MFM, both from a theoretical and applied perspective, and we illustrate the complementarity of the two approaches with an empirical application on students' satisfaction with the University of Florence. The multilevel aspect of this application is that students are nested within study programs, which makes it possible to cluster these programs based on their differences in students' satisfaction.     

The role of explicit and implicit learning processes in concept discovery

Analysis of individual learning curves and concurrent verbal protocols from three experiments concerning discovery of a non-salient verbal concept and a pictorial analogue (Chinese ideograph) of the concept show that a substantial transition phase occurs in which discrimination of exemplars from non-exemplars of the concept is above chance but not yet asymptotic. Under most conditions the ability to verbalize knowledge of the concept occurred almost simultaneously with the onset of the transition phase. However, the addition of noise in the form of false feedback (Experiment 3) created a temporary dissociation between task performance and verbalizable knowledge. Additional results suggest that individual hypothesis revision/rejection strategies affect the length of the transition phase of learning, whereas the size of the domain of hypotheses being sampled affects the number of trial blocks before the transition phase begins. The effect of feedback error on the relation between early rates of hypothesis generation and subsequent transition phase length also suggests that a strategy of quick rejection of falsified hypotheses becomes less adaptive in noisy task environments (e.g. when there are many exceptions to a rule or the concept is probabilistic). Finally, failure to find effects of variables known to affect implicit learning suggests that implicit learning processes do not play a large role in the discovery of this type of concept.     

Infants discriminate manners and paths in non-linguistic dynamic events

Do 14- to 17-month-olds notice the paths and manners of motion events? English- and Spanish-learning infants were habituated to an animated motion event including a manner (e.g., spinning) and a path (e.g., over). They were then tested on four types of events that changed either the manner, the path, both, or neither component. Both English- and Spanish-learning infants attended to changes of manner and changes of path. Thus, infants from two different language communities proved sensitive to components of events that undergird relational term learning.     

Orientation illusions vary in size and direction as a function of task-dependent attention

Adding an upright inner square frame to an outer tilted square frame causes a central rod's perceived orientation to be directionally opposite the usual rod-and-frame illusion (RFI). Zoccolotti, Antonucci, Daini, Martelli, and Spinelli (1997) attributed this double RFI (DRFI) to Rock's (1990) hierarchical organization principle. In Experiment 1, this explanation predicted results for small (11 degrees ) but not larger (22 degrees and 33 degrees ) outer frame orientations. In two experiments with the DRFI, bottom-up, goal-driven attention was varied and direct and indirect measures of the framework's influence were compared. In Experiment 2, the RFI angular function was compared with two other DRFI conditions: a direct measure of perceived rod orientation and an indirect measure of the inner frame. These conditions induced directionally opposite effects. In Experiment 3, direct and indirect measures of the inner frame's perceived tilt were compared. Angular functions differing in size and direction were obtained. Experiment 4 replicated the previous results, using a different psychophysical procedure. All the results were consistent with the hierarchical organization mechanism but suggested different processing strategies due to different attentional weights. They were also consistent with other recent findings based on the Bayesian approach to accounts of illusory phenomena (e.g., Jazayeri & Movshon, 2006, 2007; Weiss, Simoncelli, & Adelson, 2002).     

How toddlers begin to learn verbs

Any theory of language must account for how children learn verbs, the gateway to grammar. Yet verbs can be difficult to learn. Building on Gentner's 'natural partitions hypothesis' we suggest that, to learn a verb, infants must conceptualize components of events and map verbs in the ambient language onto those components. Although toddlers detect and categorize at least some of the conceptual underpinnings of verb categories, the mapping of verbs onto these representations is not transparent. Mapping is a difficult problem in its own right. The Emergentist Coalition Model that has been used to explain noun learning also begins to explain how children move from perceptual to social and then to linguistic information to link verbs to actions and events.     

Subjectivity and essential individuality: A dialogue with Peter Van Inwagen and Lynne Baker

Each person is perceived by others and by herself as an individual in a very strong sense, namely as a unique individual. Moreover, this supposed uniqueness is commonly thought of as linked with another character that we tend to attribute to persons (as opposed to stones or chairs and even non-human animals): a kind of depth, hidden to sensory perception, yet in some measure accessible to other means of knowledge. I propose a theory of strong or essential individuality. This theory is introduced by way of a critical discussion of Van Inwagen’s and Baker’s ontologies of persons. Composition Theory and Constitution Theory are shown to be complementary, in their opposite strong and weak points. I argue that both theories have unsatisfactory consequences concerning personal identity, a problem which the proposed theory seems to solve more faithfully both to folk intuitions and the phenomenology of personal life.

Theory‐Based Determinants of Youth Smoking: A Multiple Influence Approach1

This study tested a broad array of determinants of smoking grounded in general social psychological theories, as well as personality and social development theories. Using data from 2,004 middle school students, all proximal and distal determinants significantly predicted smoking in the hypothesized direction. Further, hierarchical logistic regressions showed that intention to smoke, positive and negative attitudes toward smoking, impediments to smoking, self‐efficacy to resist smoking, parent norms, and academic success most strongly predicted current smoking. Hierarchical linear regressions suggested that parental relatedness, maladaptive coping strategies, depression, and low academic aspirations most strongly predicted susceptibility to smoking for those who had not yet smoked a cigarette. Global expectancies were the strongest predictor of susceptibility in low socioeconomic status students. These findings may guide the development of future theory‐based interventions that produce the greatest reductions in youth smoking.     

Service in the Gulf War and Significant Health Problems: Focus on the Central Nervous System

The consensus of several studies on health among Gulf War (GW)-deployed veterans is that they have elevated symptom complaints. Central nervous system (CNS) symptoms among these veterans have been assessed in several investigations. Studies have disagreed as to whether there are neuropsychological deficits in GW-deployed veterans relative to controls. When differences between these groups have been found, they have often been attributed to stress or psychiatric factors, although exposures to neurotoxic substances present in the GW theatre have also been indicted as possible explanations. A review of the existing literature as well as the 5 papers contained in this issue of Journal of Psychopathology and Behavioral Assessment suggests that the neuropsychological and health symptom sequelae of GW zone service are multidetermined and cannot easily be explained on the basis of simplistic models of causation. Psychological, historical, and exposure parameters must be considered in the scientific evaluation of this problem.     

Spatial updating of multiple targets: Comparison of younger and older adults

When walking without vision, people mentally keep track of the directions and distances of previously viewed objects, a process called spatial updating. The current experiment indicates that while people across a large age range are able to update multiple targets in memory without perceptual support, aging negatively affects accuracy, precision, and decision time. Participants (20 to 80 years of age) viewed one, three, or six targets (colored lights) on the floor of a dimly lit room. Then, without vision, they walked to a target designated by color, either directly or indirectly (via a forward turning point). The younger adults’ final stopping points were both accurate (near target) and precise (narrowly dispersed), but updating performance did degrade slightly with the number of targets. Older adults’ performance was consistently worse than the younger group, but the lack of interaction between age and memory load indicates that the effect of age on performance was not further exacerbated by a greater number of targets. The number of targets also significantly increased the latency required to turn toward the designated target for both age groups. Taken together, results extend previous work showing impressive updating performance by younger adults, with novel findings showing that older adults manifest small but consistent degradation of updating performance of multitarget arrays.