I. Brain imaging methodsII. Genetic influence vs. environmental influenceGenetic influences on weight:- A child’s weight is correlated with their biological parents’ weight, regardless of whether or not they live with them. Genetic influence is stronger than environmental influence. Even with the influence of environmental changes, the weights of two related individuals will stay correlated.- Weight system evolved to protect against weight loss in times of deprivation (famine was common in the past), but not against weight gain in times of plenty.Motivation: beyond drive reduction:How can the homeostatic or drive reduction principles explain reinforcement without apparent drive reduction, thrill-seeking reinforcement from arousal, behavior with no apparent biological significance?Incentive value of aesthetics  looking at things is accompanied by release of endorphinsEx: monkey will learn to press a lever to see into another roomAttraction of uncertainty and reward from resolution of uncertainty  people are attracted to games in which there is a random component and consequent uncertainty about what will happenPunishing effect: strong negative reinforcement - will work to get rid of itRewarding effect: strong positive reinforcement – will work to get itThe Brain-Reward System:- Activity occurs in the same area of the brain (medial forebrain bundle & nucleus accumbens, which regulates dopamine and endorphin release) from: Reinforcement from natural sources. Reinforcement from direct electrical stimulation. Reinforcement from drugs.Wanting vs. Liking- Dopamine is released before certain responses (wanting), but not after the response and rewardHormones, mating, bonding:- In male prairie voles, when they mate, they become ‘addicted’ to their mate, as if it got a hit of cocaine. More vasopressin near the brain reward system- Male montane voles are the opposite- solitary and promiscuity.- This difference is due to a difference in the distribution of brain receptor sites for the home vasopressin.- Oxytocin may help mothers bond with and defendPSYC 100 1st Edition Lecture 9 Outline of Last Lecture I. Brain imaging methods Outline of Current Lecture II. Genetic influence vs. environmental influence Current LectureGenetic influences on weight: - A child’s weight is correlated with their biological parents’ weight, regardless of whether or not they live with them. Genetic influence is stronger than environmental influence. Even with the influence of environmental changes, the weights of two related individuals will stay correlated.  - Weight system evolved to protect against weight loss in times of deprivation (famine was common in the past), but not against weight gain in times of plenty.  Motivation: beyond drive reduction: How can the homeostatic or drive reduction principles explain reinforcement without apparent drive reduction, thrill-seeking reinforcement from arousal, behavior with no apparent biological significance? Incentive value of aesthetics  looking at things is accompanied by release of endorphins- Ex: monkey will learn to press a lever to see into another room  Attraction of uncertainty and reward from resolution of uncertainty  people are attracted to games in which there is a random component and consequent uncertainty about what will happen Punishing effect: strong negative reinforcement - will work to get rid of it Rewarding effect: strong positive reinforcement – will work to get it The Brain-Reward System: - Activity occurs in the same area of the brain (medial forebrain bundle & nucleus accumbens, which regulates dopamine and endorphin release) from: Reinforcement from natural sources. Reinforcement from direct electrical stimulation. Reinforcement from drugs.  Wanting vs. Liking - Dopamine is released before certain responses (wanting), but not after the response and reward Hormones, mating, bonding: - In male prairie voles, when they mate, they become ‘addicted’ to their mate, as if it gota hit of cocaine. More vasopressin near the brain reward system  - Male montane voles are the opposite- solitary and promiscuity. - This difference is due to a difference in the distribution of brain receptor sites for the home vasopressin.  - Oxytocin may help mothers bond with and