state of cheerfulness or amusement.However，behavioural ecology theory suggests that all smiles are tools used in social interactions, meaning cheerfulness is neither necessary nor rich for smiling.Our study showed that in these human­computer interaction experiments，smiling isn't driven by happiness；it is associated with subjective involvement(主观参与)，which acts like a social fuel for smiling，even when socialising with a computer on your own."

　　Surprisingly，participants didn't tend to smile during the period when they were trying to figure out the answers.However，they did smile right after the computer game informed them if their answer was correct or wrong.Participants smiled more often when they got the answer wrong.Dr Witchel added："During these computerised quizzes，smiling was greatly increased just after answering questions incorrectly.This behaviour could be explained by self­ratings of involvement，rather than by ratings of happiness or frustration."

　　【语篇解读】　本文是一篇说明文。人们普遍认为微笑意味着一个人是快乐的，但是研究表明，微笑仅是社交的需要，并不表明这个人一定是快乐的。

　　1．Why did Dr Witchel use difficult questions in the quiz game?

　　A．To make it hard for participants to answer them correctly.

　　B．To make the answer period last as long as possible.

　　C．To discover the most intelligent participants.

　　D．To create a stressful situation for participants deliberately.

　　A　[细节理解题。根据第二段第一句"In his research，he asked 44 participants aged 18-35 to play a geography quiz game consisting of nine difficult questions so that they often got the answer wrong"可知，他设计的问题很难是为了让参加试验的人得出错误的答案；据此可知，设计难题的目的是让参与者难以答对题目，故A项正确。]

　　2．What can we infer from what Dr Witchel said in Paragraph 4?

　　A．Other researchers' opinion of a real smile is quite right.

B．Smiles aren't necessarily useful tools in social interactions.