Yet , there has been so far no systematic theories , nor been any comparative studies made . thus , the results might lack credibility , or be only hypothesis without practice , or only phenomenalistic investigation and analysis of internal causes without teaching strategies , or with strategies that are not based on teaching practice 但目前还没有较系统的理论体系，研究一般没有采取对比实验研究，其结论失去可信度，或只是理论假设，根本没有进行实践，或只有现象调查及内因分析，没有教学对策，或有教学对策，但不是来自于教学实践的总结，只是推理研究。
