Andrew Huberman, Ph.D.what it claims
Absolutely avoid memorizing speeches word-for-word so as not to overload working memory (cognitive load). It is preferable to structure your presentation in the form of a roadmap, use notes for specific data, and familiarize yourself only with the introduction to calmly navigate the initial peak of stress.
The advice to avoid word-for-word memorization rests on very solid foundations in cognitive psychology and communication.
