The Role of Nicotine Metabolic Rate on Nicotine Dependence and Rewarding: Nicotine Metabolism in Chinese Male Smokers and Male Mice

The exact relationship between nicotine metabolism and dependence is not fully understood but is known to be influenced at a molecular level by genetic factors. A sample comprising 274 Chinese adult male smokers was categorized into groups based on their metabolic rates, namely fast, intermediate, and slow metabolizers. We then measured their smoking topography, evaluated their nicotine dependence, and assessed the rewarding effects. Based on these findings, we proposed the hypothesis that the rate of nicotine metabolism could influence the level of dopamine release which in turn had repercussions on the pleasurable and rewarding effects. To test this hypothesis, male mice were selected with different nicotine metabolic rates that closely resembled in the smoker group. We evaluated their nicotine dependence and rewarding effects through conditioned place preference and withdrawal symptom tests, supplemented with dopamine release measurements. In both animal and human, the slow metabolism group (SMG) required less nicotine to maintain a comparable level of dependence than the fast metabolism group (FMG). The SMG could achieve similar rewarding effects to FMG despite consuming less nicotine. Comparable dopamine levels released were therefore critical in setting the nicotine acquisition behavior in this animal model and also for the smokers tested. Our findings suggested that even within the same ethnicity of established smokers (Chinese Han), differences in nicotine metabolism were an important parameter to modulate the degree of nicotine dependence.

Preverbal infants' reactions to third-party punishments and rewards delivered toward fair and unfair agents

Rewarding individuals who distribute resources fairly and punishing those who distribute resources unfairly may be very important actions for fostering cooperation. This study investigated whether 9-month-olds have some expectations concerning punishments and rewards that follow distributive actions. Infants were shown simple animations and were tested using the violation-of-expectation paradigm. In Experiment 1, we found that infants looked longer when they saw a bystander delivering a corporal punishment to a 'fair distributor,' who distributed some windfall resources equally to the possible recipients, rather than to an 'unfair distributor,' who distributed the resources unequally. This pattern of looking times was reversed when, in Experiment 2, punishments were replaced with rewards. These findings suggest an early emergence of expectations about punishing and rewarding actions in third-party contexts, and they help to evaluate competing claims about the origins of a sense of fairness.

Owners Frequently Report that They Reward Behaviors of Dogs by Petting and Praising, Especially When Dogs Respond Correctly to Commands and Play with Their Toys

We characterized the reward patterns of dogs' owners for the expression of desired behaviors of their pets through a questionnaire made available online on a social media page for 7 days (responses from over 66,676 owners). The questions were related to the type and frequency of rewards that pet owners applied and what specific dogs' behaviors were rewarded. Desired behaviors of dogs were frequently reported to be rewarded. Responding correctly to commands and playing with their own toys were behaviors reported to be rewarded more frequently by owners than eliminating in appropriate places, a behavior perceived commonly just later. Moreover, owners reported that they rewarded more frequently by petting and praising the dogs and less frequently by applying a combination of giving both food and toys to their dogs. Thus, dog owners commonly reward desired behaviors by petting and prasing the dogs, most likely because it is the most convenient reward to use. Moreover, rewarding is more common when dogs express desired behaviors more immediately perceived by owners, which has welfare implications for these companion animals.