Task-dependent costs in processing two simultaneous auditory stimuli

A listener presented with two speech signals must at times sacrifice the processing of one signal in order to understand the other. This study was designed to distinguish costs related to interference from a second signal (selective attention) from costs related to performing two tasks simultaneously (divided attention). Listeners presented with two processed speech-in-noise stimuli, one to each ear, either (1) identified keywords in both or (2) identified keywords in one and detected the presence of speech in the other. Listeners either knew which ear to report in advance (single task) or were cued afterward (partial-report dual task). When the dual task required two identification judgments, performance suffered relative to the single-task condition (as measured by percent correct judgments). Two different tasks (identification for one stimulus and detection for the other) resulted in much smaller reductions in performance when the cue came afterward. We concluded that the degree to which listeners can simultaneously process dichotic speech stimuli seems to depend not only on the amount of interference between the two stimuli, but also on whether there is competition for limited processing resources. We suggest several specific hypotheses as to the structural mechanisms that could constitute these limited resources.     

Child and Adolescent Tobacco and Substance Use within the Context of ADHD: Implications for Prevention and Treatment

Tobacco, alcohol, marijuana, and other forms of substance use among children and adolescents is a significant public health concern. At present, one high-risk population of great concern is those affected with Attention-Deficit/Hyperactivity Disorder (ADHD) and those with subthreshold ADHD-like symptoms. The prevalence of tobacco and substance use is considerable within this population, and ADHD and ADHD-like symptoms often present as comorbid conditions. To further the understanding of this problem, a review is provided of youth tobacco and substance use and their biobehavioral influences in the context of ADHD. Using primary care as an example, opportunities for tobacco and substance use prevention and treatment within this high-risk population are examined.     

Allowing for correlations between correlations in random-effects meta-analysis of correlation matrices

Practical meta-analysis of correlation matrices generally ignores covariances (and hence correlations) between correlation estimates. The authors consider various methods for allowing for covariances, including generalized least squares, maximum marginal likelihood, and Bayesian approaches, illustrated using a 6-dimensional response in a series of psychological studies concerning prediction of exercise behavior change. Quantities of interest include the overall population mean correlation matrix, the contrast between the mean correlations, the predicted correlation matrix in a new study, and the conflict between the existing studies and a new correlation matrix. The authors conclude that accounting for correlations between correlations is unnecessary when interested in individual correlations but potentially important if concerned with a composite measure involving 2 or more correlations. A simulation study indicates the asymptotic normal assumption appears reasonable. Because of potential instability in the generalized least squares methods, they recommend a model-based approach, either the maximum marginal likelihood approach or a full Bayesian analysis.     

Adolescents’ Social Environment and Depression: Social Networks, Extracurricular Activity, and Family Relationship Influences

The present study examined components of adolescents’ social environment (social network, extracurricular activities, and family relationships) in association with depression. A total of 332 adolescents presenting for a routine medical check-up were self-assessed for social network risk (i.e., smoking habits of best male and female friends), extracurricular activity level (i.e., participation in organized sports teams, clubs, etc.), family relationship quality (i.e., cohesion and conflict), and symptoms of depression (i.e., minimal, mild, moderate/severe). Results of a forward linear regression modeling indicate that social environment components were associated with a significant proportion of the variance in adolescent depression (Adjusted R ² = .177, p ≤ .05). Specifically, adolescent females (β = .166, p < .01) and those having more smokers in their social network (β = .107, p < .05) presented with significantly greater depression symptoms. Conversely, adolescents who engaged in more extracurricular activities (β = −.118, p < .05) and experienced higher quality family relationships (β = −.368, p < .001) presented with significantly lower depressive symptoms. These findings highlight the important role that the social environment plays in adolescent depression, as well as yields new insights into socially-based intervention targets that may ameliorate adolescent depression. These intervention targets may be gender-specific, include positive social network skills training, increase adolescents’ engagement in organized activities, and attend to the quality of their family relationships.     

Successive incrementing non-matching-to-samples in rats: An automated version of the odor span task

The odor span task is a procedure frequently used to study remembering of multiple stimuli in rodents. A large arena is used and odor stimuli are presented using scented cups. Selection of each odor is reinforced when first presented, but not on subsequent presentations; correct selections depend on remembering which stimuli were previously presented. The use of an arena setting with manual stimulus presentation makes the odor span task labor-intensive and limits experimental control; thus, an automated version of the task would be of value. The present study used an operant chamber equipped with an olfactometer and trained rats using successive conditional discrimination procedures under an incrementing non-matching-to-samples contingency. High rates of responding developed to odor stimuli when they were session-novel with low rates of responding to subsequent presentations of that odor. Additional experiments assessed variations of the procedure to determine the role of the frequency of odor presentation and the retention interval separating sample and comparison. Discrimination was impaired with long retention intervals suggesting the importance of this variable. These findings confirmed that rats differentiate between stimuli that are session-novel and those previously encountered and support the use of an automated procedure as an alternative to the odor span task.     

An apparatus for studying operant activity of captive coyotes

We describe a portable apparatus designed to examine the free-operant food preferences of captive coyotes in their home kennels. Because leverpressing for food access was the dependent variable, we measured food preference independently of food ingestion. Using successive approximation, we trained 8 out of 19 coyotes (42%) to use the apparatus. This percentage is similar to training rates for dogs. We used fixed and variable ratio schedules of reinforcement to further test 4 of the trained coyotes. All 4 produced response curves similar to those of other species on similar schedules of reinforcement.     

Perceptions of absolute versus relative differences between personal and comparison health risk.

OBJECTIVE: To explain inconsistent results in previous attempts to determine whether, when presented with health risk information, people focus primarily on information about their own risk status or on a comparison with others. DESIGN: A randomized between-groups experiment in which participants were presented with hypothetical cardiac risk information. We examined whether affective responses were primarily sensitive to the relative difference between personal and comparison risk, rather than the absolute difference. MAIN OUTCOME MEASURES: Participants' negative affective response to the risk information. RESULTS: When relative differences were held constant, participants' responses were independently influenced by both personal risk and comparative standing, effects that were greatly attenuated when absolute differences were held constant. When maintaining constant absolute differences, personal and comparison risk information appeared to interact. CONCLUSION: Previous studies tended to maintain constant absolute risk differences and so may have underestimated the impact of personal risk information. Participants' responses were sensitive to the way the risk difference was constructed. Basing experimental design decisions on assumptions about the information participants will respond to can lead to misinterpretations of the basis of risk judgments.     

Illusory contour figures are perceived as occluding contours by 4-month-old infants

Although 4-month-olds perceive continuity of an object's trajectory through occlusion, little is known about the information specifying an occluding surface at this age. We investigated this in 3 experiments involving 84 participants. Testing the claim that 5-month-olds are unable to perceive the Kanizsa figure as an occluding surface (Csibra, 2001), we demonstrated that 4-month-olds perceived trajectory continuity behind this figure providing its horizontal extent was small. We demonstrated that the presence of visible occluding edges or occlusion of background was insufficient to specify an occluding surface but that their combination was sufficient. Thus, beyond object deletion and accretion, both visible occluding edges and occlusion of background are necessary for perception of occluding surfaces at this age.