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在小学数学概念教学中,经常用到反例。反例就是故意变换事物的本质属性,使之质变为其它事物,在引导思辨中,从反面突出事物的本质属性的否定例证。一、反例的功能1.反例是正确感知的需要正确的感知应以感知材料的全面、充分为前提。因此,教师提供的材料,既要有提供概括信息的肯定例证,又要有提供辨别信息的否定例证,即反例。2.反例能使学生的思维定向小学生学习概念时,发生的错误常常是有规律的。教师根据这个规律来设计反例,在所发出的信息尚未发生认识偏差之前,先把学生潜在的错误亮出来,引导学生辨析,把错误消灭在萌芽状态。3.反例能矫正学生已经形成的认知偏差儿童学习概念经常要在“发生错误——研究错误——改正错误”的过程中实现。把学生认知过程中典型的、普遍的错误作为反例,以错纠错,矫正学生认知偏差的效果会更好。4.反例有利于学生对概念进行准确的分类反例提供了有利于辨别的信息,有了这样的信息,学生才能把具有不同属性的事物分开,把具有相
In primary school mathematics concept teaching, often use counterexamples. Counterexamples are deliberate changes in the nature of things, so that qualitative change to other things, in the guidance of speculation, highlighting the negative properties of things from the negative examples. First, the counterexample of the function 1. Counterexample is the correct perception of the need for a correct perception of the perceived material should be full, full as a precondition. Therefore, the materials provided by teachers should include not only affirmative examples of general information, but also negative examples of discerning information, that is, counter examples. (2) counterexample can make students think when primary school students learn the concept of mistakes are often regular. Teachers in accordance with this law to design counterexamples, in the information issued by the understanding bias has not occurred, the students first potential error bright, and guide students to differentiate, to eliminate the mistakes in the bud. 3. Counterexample can correct the cognitive bias students have formed Learning concept of children often in the “error - research error - to correct errors” in the process. It is better to take the typical and common mistakes of students' cognition as counterexamples, to correct mistakes and correct them. 4. Counterexamples help students to classify concepts accurately Counterexamples provide information that is good for discrimination. With such information, students can separate things with different attributes,