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.     

Attachment Styles and Personality Disorders: Their Connections to Each Other and to Parental Divorce, Parental Death, and Perceptions of Parental Caregiving

Attachment theory was explored as a means of understanding the origins of personality disorders. We investigated whether adult attachment styles and personality disorders share a common underlying structure, and how both kinds of variables relate to family background factors, including parental death, parental divorce, and current representations of childhood relationships with parents. A nonclinical group of 1407 individuals, mostly adolescents and young adults, were surveyed about their attachment styles, parental marital status, parental mortality status, perceptions of treatment by parents in childhood, and 13 personality disorders. Results indicated substantial overlap between attachment and personality-disorder measures. Two of the personality-disorder dimensions are related to the two dimensions of the attachment space; that is, there is a two-dimensional space in which both the attachment patterns and most of the personality disorders can be arrayed. The one personality-disorder factor that is unrelated to attachment appears akin to psychopathy. Both personality disorders and attachment styles were associated with family-of-origin variables. Results are discussed in terms of encouraging further research to test the idea that insecure attachment and most of the personality disorders share similar developmental antecedents.     

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.     

Acute Ethanol Administration Impairs Spatial Performance While Facilitating Nonspatial Performance in Rats

Acute ethanol administration produces learning and memory impairments similar to those found following lesions to the hippocampal system in rats. For example, both ethanol and hippocampal lesions impair performance on spatial learning and memory tasks while sparing performance on many nonspatial learning and memory tasks. Lesions to the hippocampal system can also alter the nature of the information that the animal uses to guide its behavior, from using spatial information to using individual cues. In the present experiment, rats were trained, while sober, to navigate on an eight-arm radial arm maze to a specific arm for food reward. During training, the rewarded arm was always in the same specific location and contained well-defined cues. After the rat learned the task, a memory test was conducted under different doses of ethanol (0.0 g/kg [saline control], 1.0, 1.5, or 2.0 g/kg, intraperitoneal). On the test day the maze was rotated so that the cued arm was 90 degrees to the right of its original position. During testing, intact rats showed a significant bias to approach the place where they had been previously rewarded, even though the cue was no longer located there. Acute ethanol administration dose dependently reduced approaches to the rewarded place. However, ethanol administration did not result in increases in random choices; rather, it resulted in a dose-dependent increase in approaches to the cued arm, now in a new location. These results extend previous research showing that acute ethanol administration and lesions to the hippocampal system produce similar effects on learning and memory in rats.     

Psychological Dysfunction in Southeast Asian Refugees as Mediated by Sense of Coherence

Investigated Antonovky's (1979, 1987) construct of sense of coherence (i.e., an individual's belief that the world was comprehensible, manageable, and meaningful) as the internal psychological mechanism mediating the effects of external stressors (generalized resistance deficits) and resources on psychological dysfunction (measured by depression, anxiety, and psychosocial dysfunction) in 2,234 Vietnamese, Cambodian, Laotian, Hmong, and Chinese-Vietnamese refugees. Generalized resistance and deficits significantly predicted sense of coherence as well as psychological dysfunction. The amount of variance accounted for increased significantly when the mediating effect of sense of coherence was tested using a path analysis. Sense of coherence significantly reduced the predictive power of generalized resistance and deficits in the psychological dysfunction models. Results support the hypothesized mediating role of sense of coherence. Thus, interventions aiming to enhance Southeast Asian refugees' functioning may gain in effectiveness by targeting and promoting their sense of coherence.     

Comparison of the Effects of Formal and Informal Accountability on the Correct Performance of a Lifeguard Rescue

We compared instructional strategies used to train lifeguards. Fifteen undergraduates participated in the study during their twice weekly 90 minute lifeguard classes. A checklist of 15 steps was used to define correct performance of a lifeguard (water) rescue. The dependent variable was the percentage of steps completed correctly. Data were collected from videotapes of 32 sessions. A multi-treatment reversal design was used to assess the efficacy of typical peer instruction, a triad where students verbally supported one another, a triad where members used a checklist to prompt correct performance, and a instructor-mediated condition where for each 90% or better correct performance the participant received a bonus grade point. The significance of the rescue was not enough to produce competent performance, neither was peer support, nor peer-mediated instruction using a checklist, but all participants achieved 90% correct performance or better during the instructor-mediated condition. Our results suggest that the instructor-mediated condition is considerably more effective than informal accountability.     

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.