Effects of variations in the temporal distribution of reinforcements on interval schedule performance

Pigeons were exposed to variable-interval and fixed-interval schedules and schedules approximating variable-interval and fixed-interval schedules. The probabilities of the variable-interval and fixed-interval components in a mixed fixed-interval variable-interval schedule in Experiment I and the minimum and maximum interreinforcement intervals in Experiment II in a variable-interval schedule were manipulated to create intermediate schedule contingencies and contingencies approximating simple variable-interval or fixed-interval contingencies. Maximal control by time as defined by quantitative indices of the temporal pattern of response occurred as fixed-interval contingencies were approximated and minimal control occurred as variable-interval contingencies were approximated. Changes in the temporal pattern of response were systematically related to changes in the temporal distribution of reinforcements with both procedural definitions for manipulating the temporal distribution of reinforcements.     

Injury control. What psychologists can contribute.

Psychologists are inadequately represented in the injury control field, despite the size of the problem and the importance of behavioral factors in injury. Using motor vehicle injuries as an example, this article discusses modern injury control principles and the role psychologists can play in injury reduction.     

Concerted Creativity in the Digital Age: How do we Crack the Code…?

The purpose of the present article is to contribute to the development of a socio-material, situated conceptualization of creativity, in exploring music making as it becomes meaningful in performative emergence processes of the digital age. It uses the creative practices of musicians to analyse and discuss the qualities of ‘digital materials’ in a creative setting, today very often playing a critical role in the production and performance of music. Methodologically, the analysis is based on interviews with professional musicians performing at Roskilde Festival and observations inspired by the autoethnographic approach. The study concludes that creative musical emergence in performance situations of the digital age depends on an openness towards a fragility, imperilling the situation and ‘cracking’ the digital materiality.     

Laser-induced afterimages in humans

Afterimages induced by incoherent light sources have been studied as complex visual perceptions for over 200 years; however, individuals who have viewed a coherent source (a laser) on-axis have reported visual experiences unlike those observed for full-field flashes from incoherent sources. In the present study, 10 volunteers viewed all combinations of blue, green, and red laser light and background colors that matched the wavelengths of the laser sources (a total of 9 conditions). The bright focal (50 microm retinal irradiance diameter) 3-sec. exposures (approximately 9 log trolands-40% of the maximum permissible exposure level) given to the volunteers were administered as they performed a simulator tracking task. A 50/50 mirror (a mirror which reflected 50% of the laser beam into the optical pathway while allowing the 50% of the light from the visual scene to pass through the mirror) permitted simultaneous intrabeam viewing of the laser source and the scene. The volunteers were asked to report what they saw immediately after the laser was turned off and 1-min postexposure. The immediate reports indicated that the image they observed was the same color as the laser source and not the complementary color. Also, the images were of ten surrounded by well-defined borders and, regardless of laser's or background's col or, were generally red. One minute following presentation of the laser light the images seen were predominantly purple, dark or no longer present; however, the edge color when present generally appeared red. The immediate appearance of the images was inferred to be neural in nature and not photochemical. These results suggest the properties of the laser source, i.e., coherency, monochromaticity, and the laser's capacity to place an intense beam of light in a small retinal area, all contributed to the unique appearance of the postflash images.     

Using artificial life to teach evolutionary biology

This paper presents a pilot study on the use of artificial life software in an educational setting. Two groups of high school students received a standard lesson in evolutionary biology followed by a software session. The experimental group used the suite of artificial life software presented in this paper; the control group used a commercial multimedia hypertext. At the end of the software session both groups were asked to fill in a simple multiple-choice questionnaire testing the students knowledge of various aspects of evolutionary biology. The results show that the group using the artificial life software performed significantly better than the control group. We argue that the experimental group may learn more effectively because the artificial life makes it possible for students to perform experiments, a possibility not available to the control group.

The Effects of Health Threat Seriousness and Personal Efficacy upon Intentions and Behavior1

Eighty dental patients were pretested with a scale measuring health locus of control and then exposed to a persuasive communication designed to manipulate their beliefs about the seriousness of periodontal disease and their susceptibility to it. The high seriousness condition increased feelings of fear, concern, and threat as well as intentions and reported compliance with recommended oral hygiene procedures. However, patient's perceived personal efficacy in performing the recommended behavior was the most important predictor of subsequent behavior. The implications of the results for Roger's protection motivation theory are discussed.     

Relational and physical victimization within friendships: nobody told me there'd be friends like these

In past research, relational and physical forms of peer victimization have been identified that have been shown to be significantly associated with social–psychological maladjustment. These forms of victimization, although studied primarily within the group peer context, also occur within dyadic relationships such as friendships. Gender differences in friend victimization and the association between friend victimization and children's social–psychological adjustment were examined. Results showed that boys were more physically victimized by their friends than were girls. Girls were more relationally than physically victimized by their friends. Friend victimization was related to adjustment difficulties for both boys and girls; however, friend physical victimization was particularly related to boys whereas friend relational victimization was particularly related to girls. The implications of these findings for future research and intervention with victimized children are discussed.     

Friendship Interactions in Children with and without Depressive Symptoms: Observation of Emotion during Game-Playing Interactions and Post-Game Evaluations

This observational study supplements the strong and consistent link found between childhood depression and deficits in interpersonal functioning by examining the relationship between a high versus low score on the Children’s Depression Inventory (CDI) and children’s emotions when interacting with their best friends. High-CDI and low-CDI target children (n=86) were paired for videotaped game-playing with self-reported best friends. Researchers found that although high-CDI target children were not distinguishable from low-CDI peers in their displays of positive and negative emotion. However, the partners of high-CDI target children displayed significantly more negative emotion during the competitive task and significantly less positive emotion during the cooperative task than did partners of low-CDI target children. In addition, high-CDI target children and their partners reported less enjoyment of their interactions than low-CDI target children and their partners. This combination of findings suggests that depressive symptoms were associated with a relative lack of success achieving an optimal friendship interaction even under highly favorable conditions.