Use of clustering techniques in deriving psychoeducational profiles

This study explores whether a synthesis of clinical and statistical data taken from the psychoeducational reports completed on a group of 42, 9- to 11-year-old boys referred to a Child Psychiatric Outpatient Department for school-learning problems, would yield discrete clinical categories or clusters of children. An amalgamated hierarchical clustering technique which formed clusters by subjects based on a measure of euclidean distance was used. Forty-two reports were evaluated by licensed educational psychologists in five input areas: Developmental History, School History, Cognitive Functioning, Sensorimotor/Perceptual Functioning, and Academic Achievement. One of three educational placement recommendations was identified for each subject: No Educational Placement Intervention Necessary, Special Tutoring or Remediation, and Special Class Placement. Using clinical characteristic ratings given by the evaluators on each variable, a similarity-dissimilarity matrix was formed which classified subjects into four discrete clusters based on their clinical profiles. A χ² test determined that there was a significant association (p < .01) between cluster membership and educational placement recommendations.     

Modulation of an activity response with associative and nonassociative fear in the rat: A lighting differential influences the form of defensive behavior evoked after fear conditioning

Rats confronted with the onset of a light gradient display a transient increase in locomotion called theactivity response (AR) and a dark preference (Godsil & Fanselow, 2004). These experiments demonstrate that the magnitude of the AR can be blunted with Pavlovian fear-conditioning procedures via associative and nonassociative fear. Although manifested in decreased locomotion, the blunted AR effect was not due to increased freezing or immobility behaviors. Instead, rats displayed reduced rearing and an increase in a class of behaviors calledstationary activity. These results suggest that the lighting differential supplied by the cue influences the topography of defensive behavior and reduces the expression of freezing. This procedure provides a means by which to examine learned and unlearned defensive responses to the same stimulus.