Older kids are astute analysts nand know when performance merits praise and when it does not.
"performance merits"我理解为“行为的优点”他是一个东西， 怎么能够praise呢？“praise”我理解为“表扬”

感谢游牧的提醒!!重大发现,对于我来讲.其实,答题,帮助别人,也是帮助自己.看,我又学到东西了.

正如洲牧所说的,

When performance merits praise
and
when it does not (it 指performance, does指merits)

那么performance是主语,merit 是谓语, praise是宾语了.

"行为得到表扬"

查<金山词霸>2005,有:

merit:

To earn; deserve.See Synonyms at earn 1
博得；应受赏或惩参见 earn1

merit
vt.
应得；应受；值得
His work merits a prize.
他的工作值得奖赏。
He merited all the praise which had been given to him.
他理应受到人们给他的一切称赞。

值得; 应得
The suggestion merits serious consideration.
该建议值得认真考虑。
He certainly merits such a reward.
他确实应得到这样的报酬。



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前文一定是叙述到了关于performance merits的东西,于是在这里说道,

"大一点的孩子很善于分析,并且知道这个所谓的"行为判断法"什么时候会给他好的评价,什么时候不会."

词典里面的merit条里有:

Often merits An aspect of character or behavior deserving approval or disapproval:
常作 merits 功过：优缺点应予赞许或否定的性格方面或行为：
judging people according to their merits.
以其功过来判断人们

仅提供一个供参考的思路.