A computational analysis of mental image generation: evidence from functional dissociations in split-brain patients

Recent efforts to build computer simulation models of mental imagery have suggested that imagery is not a unitary phenomenon. Rather, such efforts have led to a modular analysis of the image-generation process, with separate modules that can activate visual memories, inspect parts of imaged patterns, and arrange separate parts into a composite image. This idea was supported by the finding of functional dissociations between the kinds of imagery tasks that could be performed in the left and right cerebral hemispheres of two patients who had previously undergone surgical transection of their corpus callosa. The left hemisphere in both subjects could inspect imaged patterns and could generate single and multipart images. In contrast, although the right hemisphere could inspect imaged patterns and could generate images of overall shape, it had difficulty in generating multipart images. The results suggest a deficit in the module that arranges parts into a composite. The observed pattern of deficits and abilities implied that this module is not used in language, visual perception, or drawing. Furthermore, the results suggest that the basis for this deficit is not a difficulty in simply remembering visual details or engaging in sequential processing.     

Effect of classical conditioning on an internal clock

Six experiments with rats used a psychophysical choice procedure to study the internal clock used to discriminate duration. They investigated if the clock is sensitive to the signal value (associative strength) of a stimulus. The experiments involved two types of trials. On choice trials, a stimulus lasted a short (e.g., 3 s) or long (e.g., 12 s) duration; then the rats chose between two levers. The rewarded choice depended on the duration of the stimulus. On conditioning trials, the stimulus used on choice trials was presented, but it ended without food (extinction trials) or with food (pairing trials) regardless of what the rat did. The main stimulus minus accuracy with the long stimulus. Experiment 1 showed that extinction trials increased short bias relative to training without conditioning trials or to training with pairing trials. The rest of the experiments tested explanations of these results. The same results were found when extinction trials were the same duration as the short stimulus (Experiment 2), when extinction trials were a random duration (Experiment 5), and when the signal value of the conditioned stimulus was changed in another way (Experiment 6). The effect of conditioning trials was modality specific (Experiments 3 and 4). Of the explanations considered, the best one--the only one not contradicted at least once--is that changing the signal value of a stimulus changes how the clock times the stimulus. Reducing signal value reduces the measured duration.     

Reflex modification in the rat: the inhibitory effects of intensity and frequency changes in steady tones

In laboratory rats (as in humans) a low-intensity tone that precedes a high-intensity burst of noise by approximately 100 ms can reduce the amplitude of the startle reaction elicited by the burst of noise. A series of four experiments with rats investigated the relation between the inhibitory effects of tonal frequency change and the length of the silent period (gap) preceding it. The major findings were the following: (a) A gap in an otherwise continuous pure tone inhibited startle when the gap occurred approximately 100 ms prior to the noise burst. (b) Although an increase in gap duration increased the inhibition afforded by the gap, the maximum inhibition was yielded by gaps of 100 ms and greater; this maximum was equivalent to the inhibition yielded by the presentation of a postgap tone alone. (c) A shift in tonal frequency across a 10-ms gap yielded more inhibition than did the same gap with no frequency shift; again the shift yielded equivalent inhibition to the presentation of the postgap tone alone. (d) An increase in the frequency shift increased inhibition when the shift occurred across a 10-ms gap, but not when the shift occurred across a 100-ms gap.     

The word-superiority effect under conditions that approximate reading

Observers detected a briefly flashed target letter embedded in word, pronounceable nonword, and unpronounceable nonword contexts. The word context facilitated perception under both holistic and analytical processing strategies; the facilitative effect was enhanced when processing was analytical.     

The impact of high school on social development

In reviewing the literature on the social impact of high school, six themes were identified: (1) students perceive strong norms for conformity to school rules, (2) the emphasis on conformity and control influences the quality of student/teacher relations which tend to be role bound and inflexible, (3) paths to social status continue to emphasize athletic competence, (4) peer group identification has an impact on social relations within the larger community as well as in the school setting, (5) powerlessness is felt as a result of the authoritarian approach to decision making, and (6) the overall high school environment does not enhance students' beliefs in the Bill of Rights. It was concluded that high school students have limited opportunities for flexible self-definition. As a result of the way they are treated by authority figures and the strong pressures toward conformity, many adolescents fail to learn the extent of their rights or effective strategies for the exercise of power.     

Young adults' contraceptive practices: an investigation of influences

This study investigated young adults' contraceptive behaviors and attitudes through application of a comprehensive, theoretical framework. Specifically, a social-psychological approach to understanding preventive behaviors (e.g., contraceptive practices), was developed, incorporating the Health Belief Model and other factors, which offered a means for evaluating the extent to which contraceptive behaviors were influenced by individual and group characteristics. The study group consisted of 283 unmarried students at several schools who were, on average, 19 years of age. Results suggested that effective contraceptive behavior associated most strongly with respondents' perceiving relatively few barriers to their use of contraception, their maintenance of extensive interpersonal skills, and their regarding peer norms as consistent with effective contraceptive behavior. Findings also underlined a need for continuing education about sexuality and contraception. Dangerous misinformation prevailed regarding respondents' knowledge of areas that include anatomy, physiology, and appropriate use of effective contraceptive methods. Finally, results implied a need to consider broad behavioral, social, and interpersonal issues as they relate to young adults' effective contraceptive behavior. Future studies of contraceptive risk taking are encouraged to examine both individual and social factors affecting sexual and contraceptive practices if unplanned pregnancy is to be minimized, if not eliminated.     

Validity and reliability of the EOM-EIS for early adolescents

The Extended Objective Measure of Ego Identity Status (EOM-EIS) was examined for reliability and validity among early/middle adolescent subjects. The EOM-EIS represents a combination of the Objective Measure of Ego Identity Status and a structured interview of identity status. The instrument was designed to measure ego identity with regard to occupational, religious, political, philosophical, and social contexts along ideological and interpersonal dimensions. A total of 467 students aged 12 to 18 (median = 15.73) responded to the instrument. In general the results from the analyses of reliability, validity, demographic characteristics, and psychosocial maturity yielded results which parallel the theoretical framework and the results from college-aged subjects.     

An intervention program for adolescents with behavior problems

Adolescents with behavior problems (aged 12 to 14) attending a regular public high school were in need of an intervention program. The purpose was to enhance their personal and interpersonal functioning as well as to structure a stimulating learning environment. In order to improve their social, educational, and psychological functioning, program objectives were established to help students develop the ability to listen to one another, respect others as well as their opinions, become aware of their own emotions and those of their peers, and recognize and minimize derogatory remarks toward one another. To attain these objectives, relaxation sessions, magic circle activities, art sessions, future planning groups, and decision-making groups were used. Meetings with teachers enabled them to examine and improve their attitudes and relationship with students. Upon completion of the program, the adolescents manifested less disruptive classroom behavior, increased their class participation, and displayed a more positive attitude toward school. The achievement of these behavioral changes indicates that a psychologically oriented intervention program is a feasible addition to a conventional curriculum. Teachers learned the basic skills of program formation, implementation, and evaluation, and most importantly, revitalized their attitude toward troubled students and their profession.