Generating interior search directions for multiobjective linear programming

A new multiobjective linear programming (MOLP) algorithm is presented. The algorithm uses a variant of Karmarkar's interior-point algorithm known as the affine-scaling primal algorithm. Using this single-objective algorithm, interior search directions are generated and used to provide an approximation to the gradient of the (implicitly known) utility function. The approximation is guided by assessing locally relevant preference information for the various interior directions through interaction with a decision maker (DM). The resulting algorithm is an interactive approach that makes its progress towards the solution through the interior of the constraints polytope.     

Estrogen abolishes latent inhibition in ovariectomized female rats

Estrogen is frequently prescribed as a method of birth control and as hormone replacement therapy for post-menopausal women with varied effects on cognition. Here the effects of estrogen on attention were examined using the latent inhibition (LI) behavioral paradigm. Ovariectomized (OVX) female rats were given either estrogen benzoate (EB, 10 or 100 microg/ml/kg; SC) or sesame oil vehicle. Males and OVX females receiving vehicle displayed normal LI. In contrast, LI was abolished in OVX females receiving EB. The lack of LI in OVX females receiving EB was a result of low suppression ratios, reflecting strong conditioning between the tone and the shock in these subjects even if they were pre-exposed to the tone. Thus, estrogen impaired the ability of OVX females to ignore irrelevant stimuli. Since different cognitive tasks vary in their required ability to ignore irrelevant stimuli, these results may account for some of the variations in the current literature on estrogen and cognition.     

The impact of landmark properties in shaping exploration and navigation

This study was aimed at uncovering physical and geometric properties that make a particular landmark a target of exploration and navigation. Rats were tested in a square open-field arena with additional portable corners featuring the same properties as the arena corners. It was found that the routes of progression converged upon the added corners, whether located at the arena wall or the arena center. Route convergence upon the added corners involved numerous visits to these corners. However, time spent at the added corners was relatively short compared with the arena corners, including that from which rats were introduced into the arena. There was no differential effect of testing rats in light or dark, or with a low versus a high portable corner. It is suggested that the added corners were distinct against the background of the arena enclosure, whereas the four arena corners and walls were encoded by the rats as one geometric module. This distinctness, together with the greater accessibility of the added corners, made them salient landmarks and a target of exploration. Thus, the impact of a landmark extended beyond its specific self-geometry to include accessibility and distinctness, which are contextual properties. In addition to the contextual impact on locomotor behavior there was also a temporal effect, with security initially dominating the rats’ behavior but then declining along with an increased attraction to salient landmarks. These spatiotemporal patterns characterized behavior in both lit and dark arenas, indicating that distal cues were secondary to local proximal cues in shaping routes.     

City rats: insight from rat spatial behavior into human cognition in urban environments

The structure and shape of the urban environment influence our ability to find our way about in the city. Understanding how the physical properties of the environment affect spatial behavior and cognition is therefore a necessity. However, there are inherent difficulties in empirically studying complex and large-scale urban environments. These include the need to isolate the impact of specific urban features and to acquire data on the physical activity of individuals. In the present study, we attempted to overcome the above obstacles and examine the relation between urban environments and spatial cognition by testing the spatial behavior of rats. This idea originated from the resemblance in the operative brain functions and in the mechanisms and strategies employed by humans and other animals when acquiring spatial information and establishing an internal representation, as revealed in past studies. Accordingly, we tested rats in arenas that simulated a grid urban layout (e.g. Manhattan streets) and an irregular urban layout (e.g. Jerusalem streets). We found that in the grid layout, rat movement was more structured and extended over a greater area compared with their restricted movement in the irregular layout. These movement patterns recall those of humans in respective urban environments, illustrating that the structure and shape of the environment affect spatial behavior similarly in humans and rats. Overall, testing rats in environments that simulate facets of urban environments can provide new insights into human spatial cognition in urban environments.     

Identification with groups: the role of personality and context

Is identification a product of personality or of the context? We examine this question by adopting a multidimensional conceptualization of identification (the CIDS model) that integrates research perspectives on personality and contextual effects. We investigate (Study 1) the relationships of traits to identification with the nation (students, N = 77), the army (soldiers, N = 220), and a business school (students, N = 123). Then we show that the modes of identification vary in their stability across social contexts and in their susceptibility to contextual change. Idealizing groups' symbols (“deference” identification) is especially stable across different foci of identification (Study 2): the military and former high school (soldiers, N = 188), the business school and the nation (students, = 62), and the military and one's ethnic group (soldiers, N = 95). Perceiving the group as a central part of the self (“importance” identification) is the most susceptible to contextual effects of priming values (Study 3; students, N = 80, 60) and the group's status (Study 4; students, N = 68).     

Antecedents of mirror self‐recognition of toddlers: Emotional availability,birth order,and gender

The present study employed a longitudinal design for examining the role of emotional availability of child–mother dyads, birth order of children, and their gender as determinants of mirror self‐recognition of toddlers. It was hypothesized that toddlers who maintained more optimal emotional availability with mother at the age of 12 months would tend to identify themselves more readily at the age of 20 months. We assumed further that first‐born children and females would identify themselves more readily than males and younger siblings. A sample of 54 nonrisk children and their mothers was investigated. Path analysis model showed that emotional availability partly predicted self‐recognition: responsive toddlers identified themselves more often than less responsive peers. No significant effects were found for the other scales of emotional availability. A nonlinear birth order effect was observed, with second‐born children being less likely to show mirror self‐recognition than first‐borns or third‐borns. Child gender was not significantly associated with self‐recognition at the age of 20 months. The data showed further that birth order was significantly linked with components of emotional availability. No significant correlations were found between emotional availability scores and child gender. Results were discussed in light of the different components of emotional availability, and the psychological correlates of ordinal position in the family. ©2002 Michigan Association for Infant Mental Health.     

Probabilistic assignments of sentence relations on the basis of differentially weighted interpretive cues

Recent treatments of comprehension have emphasized the role of surface structure characteristics. In many circumstances, meanings that are inferred on the basis of such cues will not be deterministic. This study investigated a probabilistic system of sentence comprehension. Hebrew-speaking university studients interpreted utterances that varied and balanced the contradictory and complementary effects of three interpretive cues. Sentence interpretations were systematically affected by the relative weights of cues that supported and opposed different interpretations. Adults therefore seemed to deploy a probabilistic strategy of assigning internal relations to a preferred alternative, a greatest composite of component likelihoods. While the present treatment emphasized a syntactic level of processing, it was suggested that the probabilistic strategy could easily accommodate pragmatic and semantic effects as well. The probabilistic strategy implies that given a conflict between interpretive cues, a decision needs to be made between alternative assignments of internal relations. It was therefore suggested that ambiguous and unambiguous utterances typically may be processed in a similar fashion; for both, more than one meaning may be processed at least in part before a single probabilistic interpretation is finally assigned to the utterance.     

Romantic Contexts, Sexual Behavior, and Depressive Symptoms among Adolescent Males and Females

In order to examine the association between sexual behavior and depressive affect among adolescents, 122 and 219 Israeli adolescents, in two separate studies, reported their romantic and sexual history, the quality of their relationships and level of depressive symptoms. Findings show that a higher level of sexual activity in short-term romantic relationships, which were low in intimacy and authenticity, was related to increased levels of depressive symptoms among females but not among males. In contrast, involvement in stable romantic relationships was not associated with increased depressive affect for either gender. Findings from a 3 month follow-up suggested that it may be that an increased level of depressive symptoms leads adolescent females to become more sexually involved in short romantic encounters.     

Linguistic Markers and Emotional Intensity

The purpose of this experiment is to explore possible relationships between the intensity of emotions and the lexical modalities for expressing those emotions. In this experiment, 60 Hebrew-speaking subjects were asked to watch four short films that aroused emotion. Two of the films gave rise to different degrees of happiness, and two produced sadness. At the end of each film, subjects were asked to report on their emotions. This experiment was based on the supposition that there is a relationship between the various lexical modalities used by the subjects when writing about their emotions and the intensity of those emotions. The lexical modalities examined included intensifiers, the use of emotion words, repetitions, the use of first person singular, the use of metaphors, and the use of exclamations, among others. This experiment supported the research hypothesis, as it confirmed that significant differences existed between the lexical modalities found in texts written with lower emotional intensity (for both happiness and sadness) and those written with greater emotional intensity.