On uniqueness in candecomp/parafac

One of the basic issues in the analysis of three-way arrays by CANDECOMP/PARAFAC (CP) has been the question of uniqueness of the decomposition. Kruskal (1977) has proved that uniqueness is guaranteed when the sum of thek-ranks of the three component matrices involved is at least twice the rank of the solution plus 2. Since then, little has been achieved that might further qualify Kruskal's sufficient condition. Attempts to prove that it is also necessary for uniqueness (except for rank 1 or 2) have failed, but counterexamples to necessity have not been detected. The present paper gives a method for generating the class of all solutions (or at least a subset of that class), given a CP solution that satisfies certain conditions. This offers the possibility to examine uniqueness for a great variety of specific CP solutions. It will be shown that Kruskal's condition is necessary and sufficient when the rank of the solution is three, but that uniqueness may hold even if the condition is not satisfied, when the rank is four or higher. The authors are obliged to Henk Kiers for commenting on a previous draft, and to Tom Snijders for suggesting a proof mentioned in the appendix.     

Selective hippocampal lesions disrupt a novel cue effect but fail to eliminate blocking in rabbit eyeblink conditioning

The classical conditioning task of blocking involves the adding of a novel but redundant stimulus to a previously trained stimulus. Both blocking and novelty detection are thought to involve the hippocampus. Previously, Solomon (1977) found that nonselective aspiration lesions of the hippocampal region eliminated blocking in rabbit eyeblink conditioning. We tested the effects of selective ibotenic acid lesions of the hippocampus on blocking, as well as on novelty detection, when training is switched from a tone conditioned stimulus (CS) to a compound tone-light CS in eyeblink conditioning. Selective hippocampal lesions did not eliminate blocking but did lead to a facilitation of conditioned response (CR) acquisition to the tone and to the light, but not to the tone-light compound. Selective hippocampal lesions disrupted a CR decrement observed in sham surgical controls when transferred from tone training to tone-light training. It appears that although selective hippocampal lesions do not eliminate blocking in eyeblink conditioning, they do disrupt novelty detection and may facilitate learning to a previously blocked cue.     

Predictors of loneliness among students and nuns in Angola and Portugal

The authors conducted 2 studies to examine the relationship between loneliness and psychosocial variables among people from Angola and Portugal. In the 1st study, the participants were 129 college students from Angola and 122 from Portugal, and in the 2nd study participants were 105 nuns from Angola and 74 from Portugal. The following instruments were administered to all participants in both studies: the Revised UCLA Loneliness Scale (D. Russell, L. Peplau, & C. Cutrona, 1980), the Neuroticism Scale (J. Barros, 1999), the Optimism Scale (J. Barros, 1998), and the Satisfaction With Life Scale (E. Diener, R. Emmons, R. Larsen, & S. Griffin, 1985). Ethnic differences were found in loneliness. The Angolan participants recorded higher scores for loneliness than did the Portuguese participants. For both samples the most prominent predictors of loneliness were neuroticism and dissatisfaction with life.     

"Not just right experiences": perfectionism,obsessive-compulsive features and general psychopathology

Individuals with obsessive-compulsive disorder (OCD) frequently report uncomfortable sensations of things not being just right ("not just right experiences"; NJREs) and a need to ritualize until they quiet these sensations. However, very little work has been conducted to empirically examine the nature and characteristics of this phenomenon. In this paper, we present two studies that systematically examine NJREs in large undergraduate samples. In Study 1, NJREs were shown to be related to both OCD features and maladaptive domains of perfectionism. In Study 2, NJREs were again significantly related to OCD features. Further, NJREs were shown to have particularly strong relationships with specific OCD symptom clusters (e.g., checking, ordering). Finally, NJREs were significantly more strongly correlated with features of OCD than symptoms from other domains of psychopathology (e.g., social anxiety, trait anxiety, worry, depression). General conclusions are drawn, and future directions are discussed.     

Mental workload while driving: effects on visual search,discrimination, and decision making

The effects of mental workload on visual search and decision making were studied in real traffic conditions with 12 participants who drove an instrumented car. Mental workload was manipulated by having participants perform several mental tasks while driving. A simultaneous visual-detection and discrimination test was used as performance criteria. Mental tasks produced spatial gaze concentration and visual-detection impairment, although no tunnel vision occurred. According to ocular behavior analysis, this impairment was due to late detection and poor identification more than to response selection. Verbal acquisition tasks were innocuous compared with production tasks, and complex conversations, whether by phone or with a passenger, are dangerous for road safety.     

Cholinergic dependence of taste memory formation: evidence of two distinct processes

Learning the aversive or positive consequences associated with novel taste solutions has a strong significance for an animal's survival. A lack of recognition of a taste's consequences could prevent ingestion of potential edibles or encounter death. We used conditioned taste aversion (CTA) and attenuation of neophobia (AN) to study aversive and safe taste memory formation. To determine if muscarinic receptors in the insular cortex participate differentially in both tasks, we infused the muscarinic antagonists scopolamine at distinct times before or after the presentation of a strong concentration of saccharin, followed by either an i.p. injection of a malaise-inducing agent or no injection. Our results showed that blockade of muscarinic receptors before taste presentation disrupts both learning tasks. However, the same treatment after the taste prevents AN but not CTA. These results clearly demonstrate that cortical cholinergic activity participates in the acquisition of both safe and aversive memory formation, and that cortical muscarinic receptors seem to be necessary for safe but not for aversive taste memory consolidation. These results suggest that the taste memory trace is processed in the insular cortex simultaneously by at least two independent mechanisms, and that their interaction would determine the degree of aversion or preference learned to a novel taste.     

Epidemiology of trauma and posttraumatic stress disorder in Mexico

Prevalence rates of trauma and posttraumatic stress disorder (PTSD) were estimated from a probability sample of 2,509 adults from 4 cities in Mexico. PTSD was assessed according to Diagnostic and Statistical Manual of Mental Disorders (American Psychiatric Association, 1994) criteria using the Composite International Diagnostic Interview (CIDI; WHO, 1997). Lifetime prevalence of exposure and PTSD were 76% and 11.2%, respectively. Risk for PTSD was highest in Oaxaca (the poorest city), persons of lower socioeconomic status, and women. Conditional risk for PTSD was highest following sexual violence, but nonsexual violence and traumatic bereavement had greater overall impact because of their frequency. Of lifetime cases, 62% became chronic; only 42% received medical or professional care. The research demonstrates the importance of expanding the epidemiologic research base on trauma to include developing countries around the world.     

Diminished performance on response-selection tasks in Type 2 diabetes

Comparisons of visual perception, response-selection, and response-execution performance were made between Type 2 diabetes mellitus patients and a matched nondiabetic control group. 10 well-controlled male patients with Type 2 diabetes without diabetic complications (M age 58 yr.) and an age and IQ-matched non-diabetic control group consisting of 13 male healthy volunteers (M age 57 yr.) were included. Significant differences were found only between the two groups on response-selection performance, which concerns the selection and preparation of an appropriate motor action.     

Psychological inertia in adolescence: Sexist attitudes and cognitive and social strategies that hinder gender equality

Current Psychology - This work analyses sexist attitudes, cognitive strategies and social attitudes in young people between 12 and 16 years of age, attending secondary education. The...