Final answer:
Two-step mental seriation is described as Transitive inference, where one deduces relationships between items in a series. It is developed during Piaget's concrete operational stage (ages 7-11).
Step-by-step explanation:
The process known as two-step mental seriation refers to the ability to arrange items along a quantitative dimension, such as length or weight, and also to infer the relationship between items not directly compared. This cognitive process is best described as Transitive inference, which is when one can deduce that if A is greater than B, and B is greater than C, then A is greater than C. This skill typically develops during Piaget's concrete operational stage of cognitive development, which ranges from about 7 to 11 years old. Transitive inference is the ability to logically order objects or ideas based on their relationship to one another. It involves making connections and drawing conclusions by using related observations.