I dont have valid research, however, it is possible to increase the level of thinking in your brain. I would suggest that awareness is the key single factor that kick starts this.

When you have awareness that you are now able to critically question and think about everything, it opens up your mind.

How do i know? Because i have lived this very situation.

What exactly do you mean by „disposition toward critical thinking“?

I would assume that any disposition toward X is a necessary condition to be able to actualize a state X (e.g. salt needs to be soluble in order to actually dissolve under the right conditions; anything that is not soluble cannot dissolve; analogously, anyone who cannot dispositionally think critically cannot actually think critically). But, again, depends on if you mean disposition in that sense.

CT Disposition is the inclination or willingness of using CT skills in a required environment. While, NEP 2020, recommends to promote these skills, it is important to explore teachers conceptualization of the term "critical thinking" 1st. Conceptualization not only deals with the theoretical and conceptual understanding of a particular term or phenomena, but it is the appropriate practical utilisation of it. Therefore, in critical thinking context, to conceptualise it, there is a must to acquire those skills and possess disposition towards critical thinking.