just a suggestion

I think it's acting or doing.

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Note added at 1 hr (2021-08-28 15:01:14 GMT)
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I think the word "Specify" works here!

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Note added at 1 hr (2021-08-28 15:03:47 GMT)
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And don't have the ability to specify ...

Arabic term (edited): عدم القدرة على تصميم الفعل الإرادي

inability to distinguish
inability to conserve

"Centration – a child will become completely fixed on one point, not allowing them to see the wider picture. For example, focusing only on the height of the container rather than both the height and width when determining what has the biggest volume."
https://en.wikipedia.org/wiki/Stage_theory

"Conservation refers to the ability to determine that a certain quantity will remain the same despite adjustment of the container, shape, or apparent size.[1] Other conservation tasks include conservation of number, substance, weight, volume, and length."
https://en.wikipedia.org/wiki/Centration

"Piaget proposed that children's inability to conserve is due to weakness in the way children think during the preoperational stage (ages 2–6)."
https://en.wikipedia.org/wiki/Conservation_(psychology)

" Egocentrism, then, refers to the inability to distinguish one's own perspective from that of others, but does not necessarily imply selfishness or conceit."
https://en.wikipedia.org/wiki/Centration

"he child is egocentric – which is they have problems distinguishing from their own perceptions and perceptions of others. "
https://en.wikipedia.org/wiki/Centration

The child is not yet able to elaborate and carry out a voluntary rationalized action/reaction/behaviour.

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Note added at 1 day 9 hrs (2021-08-29 22:58:31 GMT)
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Elaborating a voluntary act is a complex process that requires mental and social abilities and skills the child has not yet developed and acquired at this stage.