【英语时差8，16】每人都做

 In a famous public service announcement aimed at discouraging littering, people were shown littering along US roadways, followed by the image of a tearful Native American chief witnessing this neglect of the environment.   According to psychologist Robert Cialdini, such ads probably encourage the very behaviors they aim to combat.

The reason has to do with how these messages employ social norms. There are two main types of social norms--descriptive and injunctive. Descriptive norms inform by way of example. They suggest what is commonly done. Injunctive norms affect behavior by directing us toward what ought to be done--toward what is socially approved or disapproved¹.

Cialdini has conducted many studies that demonstrate the influence of descriptive norms. For example, people who park in a clean public garage are significantly less likely to litter than if they park in the same garage on a day when it is dirty with litter. In fact, calling people's attention to the litter actually increased the likelihood of their contributing to it.

The problem with the anti-littering campaign then is that its descriptive norm is counterproductive to its injunctive norm. Though the ad aims to convince people they ought not litter, the repeated images of people littering may promote littering by convincing viewers that everybody does it.

Descriptive norms can be useful in encouraging pro-environment behavior if they suggest that pro-environment behavior is the norm. Another study, this one examining what plea best encouraged hotel guests to reuse their towels, so as to conserve² energy, provides an example: "Join your fellow citizens in helping³ to save the environment." This sign was more successful than any of the signs just emphasizing the benefits of protecting the environment.  

1 disapproved   

v.不赞成( disapprove的过去式和过去分词 )

参考例句：

• My parents disapproved of my marriage. 我父母不赞成我的婚事。 来自《简明英汉词典》
• She disapproved of her son's indiscriminate television viewing. 她不赞成儿子不加选择地收看电视。 来自《简明英汉词典》

2 conserve   

vt.保存，保护，节约，节省，守恒，不灭

参考例句：

• He writes on both sides of the sheet to conserve paper.他在纸张的两面都写字以节省用纸。
• Conserve your energy,you'll need it!保存你的精力，你会用得着的！

3 helping   

n.食物的一份&adj.帮助人的，辅助的

参考例句：

• The poor children regularly pony up for a second helping of my hamburger. 那些可怜的孩子们总是要求我把我的汉堡包再给他们一份。
• By doing this, they may at times be helping to restore competition. 这样一来, 他在某些时候,有助于竞争的加强。