covert

adjective [原级]隐蔽的，秘密的；在丈夫保护下的

As the individual matures, that overt talking to oneself becomes covert talking to oneself, but thinking still shows up as a laryngeal habit.
随着个体的成熟，公开的自言自语变成了隐蔽的自言自语，但思考仍然表现为一种喉部习惯。