One particular weakness of psychology that was left implicit by Meehl is the fact that psychological theories tend to be verbal theories, permitting at best ordinal predictions. Such predictions do not enable the high-risk tests that would strengthen our belief in the verisimilitude of theories but instead lead to the practice of null-hypothesis significance testing, a practice Meehl believed to be a major reason for the slow theoretical progress of soft psychology. The rising popularity of meta-analysis has led some to argue that we should move away from significance testing and focus on the size and stability of effects instead. Proponents of this reform assume that a greater emphasis on quantity can help psychology to develop a cumulative body of knowledge. The crucial question in this endeavor is whether the resulting numbers really have theoretical meaning. Psychological science lacks an undisputed, preexisting domain of observations analogous to the observations in the space-time continuum in physics. It is argued that, for this reason, effect sizes do not really exist independently of the adopted research design that led to their manifestation. Consequently, they can have no bearing on the verisimilitude of a theory.

Meehl 隐含的心理学的一个特殊弱点是心理学理论往往是口头理论，最多只能进行有序预测。这样的预测并不能进行高风险测试，这会加强我们对理论真实性的信念，而是导致了零假设显着性测试的实践，Meehl 认为这种实践是软心理学理论进展缓慢的主要原因. 荟萃分析的日益流行导致一些人认为我们应该摆脱显着性检验，转而关注效应的大小和稳定性。这项改革的支持者认为，更加强调数量可以帮助心理学发展累积的知识体系。这项工作的关键问题是所得数字是否真的具有理论意义。心理科学缺乏一个无可争议的、预先存在的观察领域，类似于物理学中时空连续体中的观察。有人认为，由于这个原因，效果大小并不是真正独立于导致其表现的所采用的研究设计而存在的。因此，它们与理论的真实性无关。