Think-Aloud Protocol.

Think-aloud protocol (or thinking aloud; also talk-aloud protocol) is a protocol used to gather data in usability testing in product design and development, in psychology and a range of social sciences (e.g., reading, writing, translation research, decision making, and process tracing).

Think aloud protocolWikipedia
Does thinking aloud affect where people look?Measuring UJanuary 4th, 2017
Video: Understanding The Thinking Aloud Protocol For Website Usability TestingAthena Brand WisdomJune 27th, 2015
Talking Out Loud Is Not the Same as Thinking AloudUX MattersMarch 20th, 2012
Thinking Aloud: The #1 Usability ToolNielsen Norman GroupJanuary 16th, 2010