Final answer:
Adolescents who engage in hypothetico-deductive reasoning typically fail to notice variables that are not immediately suggested by the concrete materials of the task in Piaget's pendulum problem.
Step-by-step explanation:
When presented with Piaget's pendulum problem, adolescents who engage in hypothetico-deductive reasoning typically fail to notice variables that are not immediately suggested by the concrete materials of the task. They may focus only on the variables that are explicitly mentioned or easily observable, such as the length of the string or the weight of the object. This limited perspective can lead them to not consider other important variables, such as air resistance or the angle of release, which could affect the speed of the pendulum swing.