Which feature is key to Piaget's formal operational stage of cognitive development?

The key feature of Piaget's formal operational stage of cognitive development is the ability to think abstractly and logically. This stage typically begins around the age of 12 and continues into adulthood, marking a significant shift in cognitive capabilities. During this period, individuals develop the ability to formulate hypotheses, consider possibilities, and engage in systematic problem-solving. This abstract reasoning allows for the manipulation of ideas in the mind without the need for physical representations, something that is not possible at earlier stages.

In contrast, the other options reflect characteristics found in different stages of cognitive development or limitations of thought processes. Understanding physical and operational tasks is more representative of earlier stages, particularly the concrete operational stage, where children begin to grasp logical operations but still rely on concrete objects. Dependency on visual aids indicates an inability to think abstractly, common in younger children who need tangible representation to understand concepts. Meanwhile, egocentric thinking is a hallmark of the preoperational stage, where children have difficulty seeing perspectives outside of their own. Therefore, the ability to think abstractly and logically distinctly defines the formal operational stage and represents a culmination of Piaget's theory of cognitive development.