Adolescent cannabis use has grown because of increased availability and higher societal acceptance. This increase in cannabis use is problematic as adolescents who experiment with cannabis are more likely to abuse cannabis and experiment with other illicit drugs such as cocaine. The reason for the greater susceptibility to drugs use is unclear and may be the result of altered drug sensitivity after cannabis exposure. Thus, the present investigation used the behavioral sensitization paradigm to examine the behavioral response of early adolescent rats to the cannabinoid agonist CP 55,940 (CP) or cocaine after repeated cannabinoid administration. It was hypothesized that: (1) CP would cause a sensitized response in both male and female adolescent rats, (2) female rats would have a greater behavioral response than male rats, (3) pretreatment with CP would induce cross-sensitization to cocaine, (4) pretreatment with cocaine would cause behavioral sensitization and conditioned activity in male and female adolescent rats. In the first experiment, 137 male and female Sprague-Dawley rats were given CP (4, 13.2, or 40 µg/kg, IP) or vehicle (50% DMSO/H2O) once daily for 5 consecutive days on postnatal day (PD) 30- PD 34. Distance traveled and stereotyped movement was assessed for 1 h after each drug injection. After a 48 h abstinence period (i.e., on PD 36), rats were given CP (4 or 13.2 µg/kg, IP) and distance traveled and stereotyped movement was monitored for 2 h. In the second experiment, 146 male and female rats were tested with the same protocol as in Experiment 1 except that rats were given CP (13.2 or 4 µg/kg), cocaine (20 mg/kg), or vehicle (saline or 50% DMSO/H2O) for five days and then tested with saline or cocaine (10 mg/kg) after 48 h. In the first experiment, no dose of CP altered distance traveled scores or stereotyped movement over the five pre-exposure days nor did CP cause behavioral sensitization on the test day. In the second experiment, pretreatment with cocaine led to enhanced distance traveled scores and stereotyped movement when challenged with cocaine (behavioral sensitization) or saline (conditioned activity) on test day. In contrast, CP-pretreated rats did not show greater activity when injected with cocaine or saline on test day. These data show that cannabinoids do not act like psychostimulant drugs, since CP did not cause the same changes in drug sensitivity as cocaine. The cocaine sensitization observed in adolescent rats indicates that this age group is particularly vulnerable to the rewarding effects of cocaine, and suggests that early cocaine exposure can augment drug seeking behavior. The failure to detect cannabinoid-induced sensitization, conditioned activity, or cocaine cross-sensitization during adolescence suggests that CP, when given at a consistent dose, does not increase the addictive properties of cannabinoids or cocaine. The results also indicate that cannabinoid use does not alter drug responsivity or lead to greater drug seeking and abuse in the adolescent population.

The neurochemical changes occurring between the preweanling period and adolescence could be crucial for understanding the role development plays in the manifestation of psychotic behaviors. N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) fully attenuates the DA agonist-induced behaviors of adult rats, while potentiating the DA agonist-induced locomotor activity of preweanling rats. My specific hypotheses were as follows: (1) Systemically administered EEDQ would block the cocaine-induced locomotor activity of adult rats. (2) Systemically administered EEDQ would potentiate the cocaine-induced locomotion of preweanling rats. (3) EEDQ would increase the Emax values (a measure of D2 receptor sensitivity) of preweanling rats, but not adolescent or adult rats. And, (4) EEDQ would reduce dorsal striatal β-arrestin-2 (ARRB2) and GRK6 levels (measures of D2 receptor sensitivity) of preweanling rats. Behavioral results were as expected, because EEDQ attenuated the locomotion of adult and adolescent rats, while EEDQ potentiated locomotor activity of preweanling rats. EEDQ enhanced the GTPγS binding of preweanling rats, while depressing ARRB2 levels. These results are consistent with the overarching hypothesis that EEDQ causes DA supersensitivity in preweanling rats. Thus, it is here proposed that EEDQ inactivates a significant number of D2 receptors in preweanling rats, but that the remaining D2 receptors are supersensitive and capable of mediating a potentiated locomotor response.

Past research indicates that having a similar life experience as another person leads to greater empathic concern towards that person. Two studies empirically investigated if similar experiences of race-based social identity threat can increase the empathic concern of White Americans toward African Americans. Study 1 revealed that White Americans randomly assigned to think about White privilege and then randomly assigned to read a passage about an African American whose accomplishments are attributed to Affirmative Action policies (versus an African American whose accomplishments are attributed to his hard work and merit) felt greater empathic concern toward the African American described in the passage. This effect was significantly mediated by stereotype threat feelings and moderated by group identity. Study 2 revealed that White Americans randomly assigned to think about how others think they have benefited from White privilege and then randomly assigned to read a passage about an African American whose accomplishments are attributed to Affirmative Action policies (versus an African American whose accomplishments are attributed to his hard work and merit) felt greater empathic concern toward the African American described in the passage only when mediated by stereotype threat feelings or stereotype threat cognitions. This mediated effect was moderated by merit identity. This suggests that White American participants do not see the literal similarities between the scenarios of race based social identity threat to merit but can see the similarities in internal feelings and cognitions that both experiences create. Collectively, these studies suggest a novel consideration of social identity and understanding of intergroup processes.

Addiction is characterized by a progressive loss of executive control over drug-seeking and consumption, and may be associated with a behavioral shift from instrumental goal-directed actions to stimulus-response habits. Sex differences in drug addiction have been linked to changing hormone levels across the estrous cycle, and females exhibit a particular vulnerability to psychostimulants such as cocaine and amphetamines. Psychostimulants and estrogen both influence dopaminergic activity in the dorsal striatum, a region of the brain in which dopamine activity is thought to mediate the shift from action to habit. In the present set of experiments, we examined the roles of sex, amphetamine, and degree of training on habit formation in rats. To test habit formation in each experiment, animals were trained on a variable interval (VI) schedule of reinforcement to nose-poke for sucrose pellet reinforcers, then the sucrose was devalued in half of the animals by pairing its presentation with injections of lithium chloride (LiCl) to induce nausea. Animals for whom the sucrose was paired with LiCl acquired a conditioned taste aversion for the sucrose reinforcer. When tested in extinction, paired animals who remained goal-directed should inhibit their responding for the devalued sucrose, whereas animals in habit should be insensitive to the devaluation and respond at a similar rate as their non-devalued counterparts. Experiment 1 examined the role of sex in habit formation in which intact male and female rats received identical training, devaluation, and testing in two separate within-sex experiments. After 240 reinforcer exposures females exhibited habitual behavior whereas males remained goal-directed. In Experiment 2, female rats were ovariectomized (OVX) and half were given cyclic estrogen replacement. All animals received either pre-exposure to methamphetamine (METH) or vehicle. Following exposure to 120 reinforcers, a level of training that had previously been shown to be subthreshold to habit formation in males, all female groups demonstrated goal-directed responding at test, revealing a lack of effect of hormone replacement or drug pre-treatment on habit formation in OVX females at this level of reinforcer exposure. Experiment 3 aimed to determine the degree of nose-poke training that would be sub-threshold to habit formation in intact females, and two groups were given different amounts of training. Both groups exhibited habitual responding, indicating that habit threshold in females is lower than hypothesized. Overall, these experiments suggest that females shift into habitual behavior earlier in training than males, and further experiments need to be conducted to determine how factors such as hormone milieu and psychostimulant exposure influence this progression.

Introduction: Cigarette preference increases as a function of nicotine content, but preference can be shifted by manipulating cigarette cost. The aim of the present study is to model whether the behavioral-economic metric of unit price (cigarette cost/nicotine content) accounts for cigarette preference shifts and whether preference changes to very low nicotine content cigarettes (VLNCs) are associated with corresponding changes in smoking rate. Methods: 169 daily smokers from populations vulnerable to smoking completed sessions in which choices between smoking normal nicotine content (NNC) (15.8mg/g) and VLNC (0.4mg/g) cigarettes were concurrently available. In Condition 1, choices for both products were available ad-lib at an equal cost of 10 responses/choice. In Condition 2, VLNCs were again available ad-lib at 10 responses/choice, but NNCs were available on a progressive-ratio (PR) schedule wherein response cost (and unit price) increased following each NNC choice (10,160,320…8400 responses/choice). Results were analyzed using ANOVAs and a binomial test (p<.05). Results: Participants preferred NNCs over VLNCs in Condition 1, but shifted preference to VLNCs in Condition 2 (p<.001) immediately before the point in the PR progression where unit price for NNCs exceeded unit price for VLNCs (p<.001). Additionally, this preference shift corresponded with reduced total cigarette consumption compared to Condition 1 levels (p<.001). Conclusions: These results suggest that unit price of nicotine underpins cigarette preference and may provide a metric by which regulators can predict product preference and potentially impact it through policy. These results also demonstrate that VLNCs sustain lower smoking rates than NNCs even under acute laboratory conditions.

Cannabis use initiated during adolescence may precipitate lasting consequences on the brain and behavioral health of the individual. However, research on the risk factors for cannabis use during adolescence has been largely cross-sectional in design. Despite the few prospective studies, even less is known about the neurobiological predictors. This dissertation improves on the extant literature by leveraging a large longitudinal study to uncover the predictors of cannabis use in adolescent samples collected prior to exposure. All data were drawn from the IMAGEN study and contained a large sample of adolescents studied at age 14 (N=2,224), and followed up at age 16 and 19. Participants were richly characterized using psychosocial questionnaires, structural and functional MRI, and genetic measurements. Two hypothesis-driven studies focused on amygdala reactivity and two data-driven studies across the feature domains were completed to characterize cannabis use in adolescence. The first study was cross-sectional and identified bilateral amygdala hyperactivity to angry faces in a sample reporting cannabis use by age 14 (n=70). The second study determined this amygdala effect was predictive of cannabis use by studying a sample of cannabis-naïve participants at age 14 who then used cannabis by age 19 (n=525). A dose-response relationship was observed such that heavy cannabis users exhibited higher amygdala reactivity. Exploratory analyses suggested amygdala reactivity decreased from age 14 to 19 within the cannabis sample, although statistical significance was not found. In the third study, data-driven machine learning analyses predicted cannabis initiation by age 16 separately for males (n=207) and females (n=158) using data from all feature domains. These analyses identified a sparse set of shared psychosocial predictors, whereas the identified brain predictors exhibited sex- and drug-specificity. Additional analyses predicted initiation by age 19 and identified a sparse set of psychosocial predictors for females only (n=145). The final study improved on drug-specificity by performing differential prediction analyses between matched samples of participants who initiated cannabis+binge drinking vs. binge drinking only by age 16 (males n=178; females n=148). A sparse subset of psychosocial predictors identified in the third study was reproduced, and novel brain predictors were identified. Those analyses were unique as they compared two machine learning algorithms, namely regularized logistic regression and random forest analyses. These studies substantiated the use of both hypothesis- and data-driven prediction analyses applied to large longitudinal datasets. They also addressed common issues related to human addiction research by examining sex-differences and drug-specificity. Critically, these studies uncovered predictors of use in samples collected prior to cannabis-exposure. The identified predictors are therefore disentangled from consequences of use. Results from all studies inform etiological mechanisms influencing cannabis use in adolescence. These findings can also be used to stratify risk in vulnerable adolescents and inform targets for interventions designed to curb use.

Members of the legal system (e.g., experts, jurors, investigators) are often skeptical of the information provided by intoxicated witnesses given the negative stigma surrounding alcohol and memory. However, studies examining the relationship between alcohol and witness memory often find that alcohol has no effect on peoples’ recall or their ability to identify a previously seen face. While insightful, the validity of these findings has been questioned given the low-moderate blood alcohol concentration (BAC) levels tested in these predominantly laboratory-based studies, which may not be high enough to consistently expose the cognitive deficits alcohol is expected to create. The present study examined how elevated BAC levels affect witnesses’ recall. In addition, it examined how identification format (i.e., showup versus lineup) impacts witnesses’ identification decisions at elevated BAC levels. Bar patrons (N = 132) were asked to participate in a study examining the effects of alcohol on cognitive and motor functioning. Consenting patrons’ BAC levels were recorded and they were given instructions for their first motor task. Midway through this task a confederate intruder entered the room and caused a disturbance. Participants were then asked to recall the intrusion via a mock interview and identify the intruder from a lineup or showup in which she was pictured (target-present) or was not pictured (target-absent). This procedure yielded participants with BAC levels as high as .24%. Linear regressions showed that elevated BAC levels reduced both the quantity and quality of information provided by participants. Logistic regressions showed that alcohol had no effect on identification decisions, regardless of identification format or target presence. These data highlight the importance of testing witnesses’ memory across a broad BAC spectrum and suggest that the legal system may benefit from expert information on alcohol’s lack of effect on memory for faces, despite what jurors may believe.

At least three general subgroups of students display problems with their overall academic achievement: students with motivational deficits, students with academic performance deficits, and students with a combination of both types of deficits. The prevalence of students with both behavioral and learning problems has been reported to be between 10% and 25% and as high as 50%. The current study evaluated the effects of positive reinforcement and instructional strategies on the co-occurrence of motivational and academic deficits within three experiments. Experiments 1 and 2 were conducted with four school-aged children in a behavioral outpatient clinic. Experiment 3 was conducted with three school-aged children during extended behavioral evaluations. Experiment 1 evaluated the effects of positive reinforcement and an instructional strategy on the children's preference for academic work tasks and their academic performance. Experiment 2 evaluated the effects of instructional strategies on the children's problem behavior and academic performance. Experiment 3 evaluated the effects of positive reinforcement and instructional strategies on the children's preference for academic work tasks, academic performance, and problem behavior. The results of this study showed that (a) preference for an academic task changed with the addition of positive reinforcement (Experiment 3) or an instructional strategy (Experiment 1), (b) problem behavior decreased with the addition of an instructional strategy (Experiments 2 and 3), and (c) academic performance increased with the addition of an instructional strategy (all experiments). These results suggested that positive reinforcers and/or instructional strategies function as motivating operations by abolishing the value of negative reinforcement, thereby resulting in improved academic performance and decreased occurrences of problem behavior.

Because of the rapid advancements being made in the field of knowledge, educators, as well as those in other fields, must periodically take inventory. Current practices, policies, and methods must be carefully scrutinized to determine if they are the most effective. The group or class method of instruction is one such area. The current philosophy of education held in many parts of the United States today places a great deal of importance upon the individual child. Numerous programs have been inaugurated to give the individual child as much attention as possible and still be able to have a class large enough to be practical financially. This task becomes increasingly difficult when the range of abilities within each classroom is so great. It isn't uncommon in the upper elementary and secondary classes to find a spread of from six to nine years difference in ability or achievement within one classroom. Not only do we have the problem of range within the classroom, but with the increasing school population of today, classes have grown to a prohibitive size. Add these and other problems that stem from the pressures of present day society together, and even with the best possible teacher, we get only average results.

Grouping students with in the school setting has long been a concern to all those associated with the educative process. Much investigation has been devoted to the position of level of aspiration as influential motive forces for educational, occupational, and social achievement. Many avenues of grouping have been investigated and some very thoroughly. However, research concerning grouping in relation to level of aspiration in the school setting appears to be extremely limited. This study is designed to further investigate this issue. It might be said that this study consists of essentially two phases: (1) the development of instruments for measuring classroom aspiration, social aspiration, and educational aspiration; and (2) the determination of level of aspiration relationships which exist between junior high school boys grouped on the basis of ability and those randomly assigned to a classroom.