毛泽东的信仰轨迹：从有神论到无神论

1893年,毛泽东出生在湖南一个偏僻闭塞的山村,像大多数中国农村妇女一样,母亲高氏信佛。因为头两个孩子在襁褓中夭折,所以毛泽东出生后,高氏曾多方祈求神佛保佑,虔诚吃“观音斋”。关于童年的生活,毛泽东说:“我父亲早年和中年都不信神,可是我母亲却是一个虔诚的佛教徒。她向自     

Errors in children's subtraction

Many of the errors that occur in children' subtraction are due to the use of incorrect strategies rather than to the incorrect recall of number facts. A production system is presented for performing written subtraction which is consistent with an earlier analysis of the nature of such a cognitive skill. Most of the incorrect strategies used by schoolchildren can be accounted for in a principled way by simple changes in the production system, such as the omission of individual rules or the inclusion of rules appropriate to other arithmetical tasks. The production system model is evaluated against a corpus of over 1500 subtraction problems done by 10-year olds and is shown to account for about two-thirds of the (nonnumber fact) errors. It also provides an alternative, simpler interpretation of the subtraction errors analysed by Brown and Burton (1978). Some implications for teaching are discussed.