Peer Effects in Drug Use and Sex Among College Students

Past research suggests that congregating delinquent youth increases their likelihood of problem behavior. We test for analogous peer effects in the drug use and sexual behavior of male (n = 279) and female (n = 435) college students, using data on the characteristics of first-year roommates to whom they were randomly assigned. We find that males who reported binge drinking in high school drink much more in college if assigned a roommate who also binge drank in high school than if assigned a nonbinge-drinking roommate. No such multiplier effect is observed for females, nor are multiplier effects observed for marijuana use or sexual behavior for either males or females. Students who did not engage in these behaviors in high school do not appear to be affected by their roommates high school behavior.     

The early origins and development of the scatterplot

Of all the graphic forms used today, the scatterplot is arguably the most versatile, polymorphic, and generally useful invention in the history of statistical graphics. Its use by Galton led to the discovery of correlation and regression, and ultimately to much of present multivariate statistics. So, it is perhaps surprising that there is no one widely credited with the invention of this idea. Even more surprising is that there are few contenders for this title, and this question seems not to have been raised before.This article traces some of the developments in the history of this graphical method, the origin of the term scatterplot, the role it has played in the history of science, and some of its modern descendants. We suggest that the origin of this method can be traced to its unique advantage: the possibility to discover regularity in empirical data by smoothing and other graphic annotations to enhance visual perception.     

Cognitive processes in the reflective-impulsive cognitive style

In this study, the authors improved the understanding of the cognitive processes underlying the reflective-impulsive cognitive style (RI), which was initially measured by J. Kagan, B. L. Rosman, D. Day, J. Albert, and W. Phillips (1964) on the Matching Familiar Figures Test (MFFT). The authors determined the relationships between the RI style and the cognitive factors, which would be likely to explain different MFFT solving modes-field dependence or independence as a cognitive style, the g factor, the spatial factor, and a metacognitive control index, which the authors developed for this study. The hypotheses were largely based on various studies (J. P. Ancillotti, 1984, 1985; J. Kagan, B. L. Rosman, D. Day, J. Albert, & W. Phillips, 1964; T. Zelniker & W. E. Jeffrey, 1976; T. Zelniker, A. Renan, I. Sorer, & Y. Shavit, 1977). The results are presented separately for each of four groups: (a) reflective individuals, who implement an analytic process and are cognitively mature; (b) impulsive individuals, who use a holistic process and are cognitively immature; (c) fast-accurate individuals, who are capable of implementing both analytic and holistic processes and exhibit cognitive maturity; and (d) slow-inaccurate individuals, who exhibit good metacognitive control but have trouble implementing both types of processing.     

The lengthening effect revisited: A reply to Prinzmetal and Wilson (1997) and Masin (1999)

In the present study, the lengthening phenomenon (Tsal & Shalev, 1996), namely, the increase in perceived length of unattended lines, was reexamined in light of criticisms by Prinzmetal and Wilson (1997) and Masin (1999). Prinzmetal and Wilson suggested that the effect was not due to attentional factors but to the spatial interaction between the attended line and the cue used to direct attention. We have replicated the lengthening effect when both attended and unattended lines are preceded by cues at a nearby location, showing that the effect is not caused by spatial cues per se, but instead reflects an inherent property of the attentional system. Masin argued that the lengthening effect is not robust, because it occurs for some but not for all participants. In the present study, the lengthening effect was highly reliable, occurring for each participant for a variety of line lengths.     

Lasting increases in basolateral amygdala activity after emotional arousal: implications for facilitated consolidation of emotional memories

Manipulations that reduce or enhance the activity of basolateral amygdala (BLA) neurons in the minutes to hours after training have been shown to respectively impair or facilitate retention on the inhibitory avoidance task. Although this suggests that BLA activity is altered after emotional arousal, such changes have not been directly demonstrated. To test this, we devised a feline analog of the inhibitory avoidance task and recorded BLA unit activity before and after a single inescapable footshock. Single-unit recordings revealed that the firing rate of many BLA neurons gradually increased after the footshock, peaking 30-50 min post-shock and then subsiding to baseline levels 2 h later. During this period of increased activity, the discharges of simultaneously recorded BLA cells were more synchronized than before the shock. Although it was known that pairing innocuous (conditioned stimulus, CS) and noxious stimuli modifies the responsiveness of BLA neurons to the CS, our results constitute the first demonstration that emotional arousal produces lasting increases in the spontaneous firing rates of BLA neurons. We propose that these changes in BLA activity may promote Hebbian interactions between coincident but spatially distributed activity patterns in BLA targets, facilitating the consolidation of emotional memories.     

Public and private heart rate feedback in social phobia: a manipulation of anxiety visibility

According to cognitive behavioural models of social phobia, bodily symptoms are the main source of information concerning social evaluation for social phobics. Experience and perception of bodily symptoms therefore play an important role in social anxiety. In this study we evaluated the effects of anxiety visibility on patients and controls using feedback of veridical heart sounds. A total of 32 social phobics and 32 controls were asked twice to sit in a chair and appear relaxed while being evaluated. Half of the participants heard their heart sounds first via headphones and then via loudspeakers which were also audible to observers. The presentation order of the heart sound was reversed for the other half of the subjects. Social phobics reported substantially more anxiety than controls. Both groups showed habituation in heart rate from the first to the second presentation, and both groups reported perception of a higher heart rate, but only social phobics reported significantly more anxiety and were more worried about their heart rates in the public than in the private condition. These effects were in excess of actual heart rate differences. In conclusion, social phobics worried about the broadcast of a bodily anxiety symptom, whereas controls did not. Information about arousal made public has a strong potential to increase anxiety levels in social phobics.     

The role of bottom-up processing in perceptual categorization by 3- to 4-month-old infants: simulations and data

Disentangling bottom-up and top-down processing in adult category learning is notoriously difficult. Studying category learning in infancy provides a simple way of exploring category learning while minimizing the contribution of top-down information. Three- to 4-month-old infants presented with cat or dog images will form a perceptual category representation for cat that excludes dogs and for dog that includes cats. The authors argue that an inclusion relationship in the distribution of features in the images explains the asymmetry. Using computational modeling and behavioral testing, the authors show that the asymmetry can be reversed or removed by using stimulus images that reverse or remove the inclusion relationship. The findings suggest that categorization of nonhuman animal images by young infants is essentially a bottom-up process.     

Eye movements do not reflect retrieval processes: limits of the eye-mind hypothesis

Abstract— This research investigated whether eye movements are informative about retrieval processes. Participants learned facts about persons and locations, and the number of facts (fan) learned about each person and location was manipulated. During a subsequent recognition test, participants made more gazes to high-fan facts than to low-fan facts, and gazes to high-fan facts had a longer duration than gazes to low-fan facts. However, there was no relation between the order in which items were fixated and the relative effect of person or location fan. The effect of person and location fan on gaze duration also did not differ with whether it was the person or location being fixated. A model assuming that the process of retrieval is independent of eye movements was successfully fit to the data on the distribution of gaze durations. According to this model, the effect of fan on number of gazes and gaze duration is an artifact of the longer retrieval times for high-fan facts.     

The metrics of spatial distance traversed during mental imagery

The authors conducted 2 experiments to study the metrics of spatial distance in a mental imagery task. In both experiments, participants first memorized the layout of a building containing 10 rooms with 24 objects. Participants then received mental imagery instructions and imagined how they walked through the building from one room to another. The authors manipulated Euclidean distance involved in these imaginary motions: Spatial distance measured in centimeters on the layout was either short or long. Independently, they varied categorical distance: The motions led through one room or two rooms. The time needed to imagine motions and response times to test probes indicated that both Euclidean distance and categorical distance affected mental imagery. The authors discuss the new finding of categorical distance effects in mental imagery and relate the results to earlier failures to find Euclidean distance effects in formally equivalent studies of narrative comprehension.