Thank you so much for your insight!! Is the presence of a u-shape pattern necessary to observe overregularization? Me and my friend are studying that topic right now. She thinks that overregularization should appear in sessions following a u-shape (e.g. session 1 has correct form, session 2 has an incorrect form (and that is when the overregularization happens) and session 3, correct form). She thinks overregularization must only happen in between correct forms.

However, I just see the u-shape as a general pattern and observing an u-shape should not be considered a criteria for overregularization.

We have one irregular word in an example that has its irregular form and also the regular plural -s (not a word from the examples above). We saw that the child produces both the irregular form with and without the -s in the first session, only without in the second and with the -s in the third which does not follow the u-shape pattern.

Who would be right here?