In the context of 'Learning Curves', when the learning speed is very slow at the beginning of learning, gradually increases with practice, and finally slows down again at the end, what is this type of curve called among the following?

Learning curves highlight the relationship between the amount of learning and effort or time. In an S-shaped curve, learning is slow at the beginning, accelerates in the middle part, and finally slows down or stabilizes at the end as the maximum limit of learning (Plateau) approaches. This type of curve is called a mixed or S-shaped learning curve.