A study of the classification capabilities of neural networks using unsupervised learning: A comparison withK-means clustering

Several neural networks have been proposed in the general literature for pattern recognition and clustering, but little empirical comparison with traditional methods has been done. The results reported here compare neural networks using Kohonen learning with a traditional clustering method (K-means) in an experimental design using simulated data with known cluster solutions. Two types of neural networks were examined, both of which used unsupervised learning to perform the clustering. One used Kohonen learning with a conscience and the other used Kohonen learning without a conscience mechanism. The performance of these nets was examined with respect to changes in the number of attributes, the number of clusters, and the amount of error in the data. Generally, theK-means procedure had fewer points misclassified while the classification accuracy of neural networks worsened as the number of clusters in the data increased from two to five.Acknowledgements: Sara Dickson, Vidya Nair, and Beth Means assisted with the neural network analyses.     

Borderline personality disorder and laboratory-induced cold pressor pain: Evidence of stress-induced analgesia

Behavioral neuroscience findings regarding stress-induced analgesia may be an appropriate model for the paradoxical effects of self-mutilative pain of patients with borderline personality disorder (BPD). We hypothesized that BPD patients would show an exaggerated antinociceptive effect from an uncontrollable cold pressor stress, compared to persons with other personality disorders or to a nonpsychiatric control group. This hypothesis was supported. Limitations of the study and directions for future research are discussed.     

The Structure of Anxiety and Depression in a Normative Sample of Younger and Older Australian Adolescents

It has been reported that depression and anxiety have overlapping symptoms and are conceptually interrelated. One of the most prominent theoretical developments that explain this association is Clark and Watson’s tripartite model (Journal of Abnormal Psychology, 100:316–336, 1991) that posits these two disorders and negative emotions share a latent component of negative affect (NA). The current study had two aims, (a) to compare a tripartite factor structure against competing models by Confirmatory Factor Analysis (CFA) of the Depression Anxiety and Stress Scales (DASS-21) (Lovibond and Lovibond 1995), and (b) explore the psychometric properties of the DASS-21. The DASS-21 was completed by a representative sample of 4039 young Australians, aged 12–18 years, as part of the South Australian Youth Mental Health Survey (SAYMHS), South Australia, Australia. The best fitting model for the data consisted of anhedonic depression, physiological hyperarousal, and general NA. The psychometric properties of the DASS-21 were excellent with a stable and interpretable factor structure and good internal consistency. The results of the current study suggest that the theoretical tripartite structure of depression and anxiety is robust and applicable among Australian youth. The diagnostic, clinical and theoretical implications of these findings are discussed.     

Electrophysiological evidence for size invariance in masked picture repetition priming

This experiment examined invariance in object representations through measuring event-related potentials (ERPs) to pictures in a masked repetition priming paradigm. Pairs of pictures were presented where the prime was either the same size or half the size of the target object and the target was either presented in a normal orientation or was a normal sized mirror reflection of the prime object. Previous masked repetition priming studies have found a cascade of priming effect sensitive to perceptual (N190/P190) and semantic (N400) properties of the stimulus. This experiment found that both early (N190/P190 effects) and later effects (N400) were invariant to size, whereas only the N190/P190 effect was invariant to mirror reflection. The combination of a small prime and a mirror reflected target led to no significant priming effects. Taken together, the results of this set of experiments suggests that object recognition, more specifically, activating an object representation, occurs in a hierarchical fashion where overlapping perceptual information between the prime and target is necessary, although not always sufficient, to activate a higher level semantic representation.     

Intergenerational Fusion and Nuclear Family Functioning

Bowen theory hypothesizes that undifferentiation or fusion between the generations influences nuclear family functioning. Using qualitative and quantitative methods this longitudinal study tested this idea with 49 newly developing nuclear families. Analysis of the first five years of data offered support to the hypothesis. Qualitative analyses of the participants' interviews gave the strongest support for higher levels of intergenerational fusion being associated with higher levels of nuclear family symptomology. Quantitative analyses also supported the hypothesis. The association between intergenerational fusion, as measured by couple-parent fusion and family financial dependence, and nuclear family functioning increased over the five-year period.     

Using Mnemonics to Increase Early Literacy Skills in Urban Kindergarten Students

The purpose of this study was to examine the effects of an integrated mnemonics strategy on consonant letter naming and consonant sound production on three kindergarten students at-risk for academic failure. Flashcards were developed where the target capital letter was enhanced and imbedded as part of the known picture (e.g., the letter D as the doorknob on a door, the letter F as the flag and flagpole). The mnemonic strategy was assessed using a multiple baseline across students design. Results showed that all three students increased in both the number of consonants named and the number of consonant sounds produced. In addition, all three students maintained performance at the 1 and 3 week followup. Also, based on a pre- and post-assessment, 2 students demonstrated generalization to the ability to name words beginning with consonants letter-sound learned.     

Perceived versus used workplace flexibility in Singapore: predicting work-family fit

This study examined the relationship of 2 types of workplace flexibility to work-family fit and work, personal, and marriage-family outcomes using data (N = 1,601) representative of employed persons in Singapore. We hypothesized that perceived and used workplace flexibility would be positively related to the study variables. Results derived from structural equation modeling revealed that perceived flexibility predicted work-family fit; however, used flexibility did not. Work-family fit related positively to each work, personal, and marriage-family outcome; however, workplace flexibility only predicted work and personal outcomes. Findings suggest work-family fit may be an important facilitating factor in the interface between work and family life, relating directly to marital satisfaction and satisfaction in other family relationships. Implications of these findings are discussed.     

INCREASING HANDICAPPED PRESCHOOLERS' PEER SOCIAL INTERACTIONS: CROSS-SETTING AND COMPONENT ANALYSIS

The purposes of our study were: (a) to train a set of observationally determined social behaviors via peer initiation; (b) to determine if effects generalized across classroom settings and to directly intervene if generalization did not occur; and (c) to analyze components of the peer-initiation intervention. After baseline, nonhandicapped preschool children (confederates) were taught to direct social initiations to the three handicapped preschool-aged students. Teachers prompted the confederates to engage the students in social interaction when necessary and rewarded the confederates with tokens. Confederates' initiations to the students resulted in increased frequencies of positive social interaction. There was no generalization to other classroom settings, and the intervention was subsequently implemented in a second and third classroom. Next, the confederates' token reinforcement system was withdrawn, with no apparent deleterious effects on the confederates' or students' social interactions. When teachers substantially reduced their prompts to the confederates, students' social interactions decreased. Finally, reinstatement of teacher prompts resulted in increases in the confederates' social initiations and, consequently, the positive social interactions of the students.     

Group comparisons of DSM-IV subtypes of chronic depression: validity of the distinctions, part 2

The nosology of chronic depression in Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV, American Psychiatric Association, 1994) is highly complex and requires clinicians to differentiate among several chronic course subtypes. This study replicates an earlier investigation (J. McCullough et al., 2000; see record 2000-05424-007) that found few differences among Diagnostic and Statistical Manual of Mental Disorders (3rd ed. rev.; DSM-III-R; American Psychiatric Association, 1987) categories of chronic depression. In the present study, 681 outpatients with chronic major depression, double depression, recurrent major depression without full interepisode recovery, and chronic major depression superimposed on antecedent dysthymia were compared. Few differences were observed on a broad range of demographic, clinical, psychosocial, family history, and treatment response variables. The authors suggest that chronic depression should be viewed as a single, broad condition that can assume a variety of clinical course configurations.