Who is being deceived? The experimental demands of wearing a backpack

A growing literature argues that wearing a heavy backpack makes slopes look steeper and distances seem longer (e.g., Proffitt, 2006). To test for effects of experimental demand characteristics in a backpack experiment, we manipulated the experimental demand of the backpack and then used a postexperiment questionnaire to assess participants’ beliefs about the purpose of the backpack. For participants in the low-demand condition, an elaborate deception was used to provide an alternative explanation of the requirement to wear a heavy backpack (i.e., that it held EMG equipment). The highest slope judgments were found for those undeceived participants who guessed that the backpack was intended to affect their slope perception and also reported that they thought they were affected by it. When persuaded that the backpack served another purpose, participants’ slope estimates were no different from those of participants not wearing a backpack. These findings suggest that backpack effects, and other reported effects of effort on perception, are judgmental biases that result from the social, not physical, demands of the experimental context.     

Estimating distance in real and virtual environments: Does order make a difference?

In this investigation, we examined how the order in which people experience real and virtual environments influences their distance estimates. Participants made two sets of distance estimates in one of the following conditions: (1) real environment first, virtual environment second; (2) virtual environment first, real environment second; (3) real environment first, real environment second; or (4) virtual environment first, virtual environment second. In Experiment 1, the participants imagined how long it would take to walk to targets in real and virtual environments. The participants’ first estimates were significantly more accurate in the real than in the virtual environment. When the second environment was the same as the first environment (real-real and virtual-virtual), the participants’ second estimates were also more accurate in the real than in the virtual environment. When the second environment differed from the first environment (real-virtual and virtual-real), however, the participants’ second estimates did not differ significantly across the two environments. A second experiment, in which the participants walked blindfolded to targets in the real environment and imagined how long it would take to walk to targets in the virtual environment, replicated these results. These subtle yet persistent order effects suggest that memory can play an important role in distance perception.     

The effect of stress on craving for methadone depends on the timing of last methadone dose

Background

This study examined the extent to which the timing of last methadone dose moderates the influence of a laboratory stressor on craving for methadone in a sample of methadone maintenance patients.

Methods

Methadone maintenance patients (N = 41) completed a computerized stress manipulation with two levels (low and high stress) on two separate days: (1) immediately following the administration of their standard daily methadone dose and (2) immediately prior to receiving their standard daily dose. The impact of stress, timing of methadone dose and their interaction were examined on self-report measures of stress and craving for methadone.

Results

Craving ratings varied according to the timing of last methadone dose. Immediately following methadone dose (i.e., day 1), there was no effect for stress on craving (0.12; p = 0.30). However, prior to receiving methadone dose (i.e., day 2), the high stress effect on craving was significant (1.51; p < 0.001).

Discussion

The present findings indicate that patients currently receiving methadone maintenance treatment may be particularly vulnerable to stress-related relapse immediately prior to daily methadone dosing.     

Does the neighborhood context alter the link between youth's after-school time activities and developmental outcomes? A multilevel analysis

This article examines links between different measures of after-school time activity participation (5 specific activities and breadth) on youth's developmental outcomes (anxiety/depression, delinquency, and substance use) over 6 years and whether these links are moderated by neighborhood-level variables. The sample (N=1,315) of 9- and 12-year-old youth was drawn from the Project on Human Development in Chicago Neighborhoods (PHDCN), a multilevel, longitudinal study of youth from 80 Chicago neighborhoods. Findings revealed that different types of activities and patterns of participation over time were associated with outcomes for youth and that, to some extent, these outcomes varied with neighborhood characteristics. In brief, sports participation was associated with fewer anxious/depressed symptoms, higher average delinquency scores, and increased substance use-both average scores and growth over time. Participation in the arts and student government were negatively associated with average substance use and attenuated increases in usage over time. Participation in community-based clubs was positively associated with youth's anxiety/depression in violent neighborhoods only, whereas church groups were protective against substance use in nonviolent neighborhoods. The direction of the influence of breadth of participation was nonlinear for delinquency such that delinquency scores were highest among youth who engaged in an average number of activities.     

How do biases in spatial memory change as children and adults are learning locations?

This investigation tracked changes in categorical bias (i.e., placing objects belonging to the same spatial group closer together than they really are) while 7-, 9-, and 11-year-olds and adults were learning a set of locations. Participants learned the locations of 20 objects marked by dots on the floor of an open square box divided into quadrants. At test, participants attempted to place the objects in the correct locations without the dots and boundaries. In Experiment 1, we probed categorical bias during learning by alternating learning and test trials. Categorical bias was high during the first test trial and decreased over the second and third test trials. In Experiment 2, we manipulated opportunities for learning by providing participants with either one, two, three, or four learning trials prior to test. Participants who experienced one or two learning trials exhibited more bias at test than did those who experienced four learning trials. The discussion focuses on how categorical bias emerges through interactions between the cognitive system and task structure.     

How Do Opportunities to View Objects Together in Time Influence Children's Memory for Location?

We conducted three experiments to investigate how opportunities to view objects together in time influence memory for location. Children and adults learned the locations of 20 objects marked by dots on the floor of an open, square box. During learning, participants viewed the objects either simultaneously or in isolation. At test, participants replaced the objects without the aid of the dots. Experiment 1 showed that when the box was divided into quadrants and the objects in each quadrant were categorically related, 7-, 9-, and 11-year-olds and adults in the simultaneous viewing condition exhibited categorical bias, but only 11-year-olds and adults in the isolated viewing condition exhibited categorical bias. Experiment 2 showed that when the objects were categorically related but no boundaries were present, 11-year-olds and adults in the simultaneous viewing condition exhibited categorical bias, but only adults showed bias in the isolated viewing condition. Experiment 3 revealed that adults exhibited bias in both simultaneous and isolated viewing conditions when boundaries were present but the objects were not related. These findings suggest that opportunities to see objects together in time interact with cues available for grouping objects to help children form spatial groups.     

Sex drive, attachment style, relationship status and previous infidelity as predictors of sex differences in romantic jealousy

Recent research examining sex differences in jealousy suggests that more men than women tend to be distressed by sexual infidelity, and that more women than men tend to be distressed by emotional infidelity. The primary explanation for these findings is that evolution has shaped men’s and women’s responses to enhance their chances of reproductive success. However, within-sex differences are also found in terms of relative level of distress at sexual or emotional infidelity. This study examined the effect of alternative variables, particularly those associated with attachment and sexual motivations, on both between- and within-sex differences in relative distress at sexual and emotional infidelity. A community sample of 437 adults provided data using a self-report questionnaire. The results showed that sex drive was a significant predictor of distress at jealousy for both men and women, while attachment avoidance and previously being the victim of a sexual infidelity were significant predictors for men only, and relationship status was a significant predictor for women only. Overall, these findings support the evolutionary model of jealousy, and suggest that sex-specific evolved psychological mechanisms underpinning jealousy are influenced by attachment and sexual motivations.     

Classroom social experiences as predictors of academic performance

A model linking children's peer acceptance in the classroom to academic performance via academic self-concept and internalizing symptoms was tested in a longitudinal study. A sample of 248 children was followed from 4th to 6th grade, with data collected from different informants in each year of the study to reduce respondent bias. A path analysis supported the model; a lack of peer acceptance in the classroom in 4th grade predicted lower academic self-concept and more internalizing symptoms the following year, which in turn, predicted lower academic performance in 6th grade. An alternative path with internalizing symptoms predicting declines in peer acceptance was tested and received some support as well. Implications of the findings for schools are discussed.     

Does information about what things are influence children's memory for where things are?

Two experiments examined how information about what objects are influences memory for where objects are located. Seven-, 9-, and 11-year-old children and adults learned the locations of 20 objects marked by dots on the floor of a box. The objects belonged to 4 categories. In one condition, objects belonging to the same category were located in the same quadrant of the box. In another condition, objects and locations were randomly paired. After learning, participants attempted to replace the objects without the aid of the dots. Children and adults placed the objects in the same quadrant closer together when they were related than when they were unrelated, indicating that object information led to systematic biases in location memory.