Final answer:
The child's belief that playing with a toy truck would change their gender reflects Kohlberg's gender stability stage in cognitive development, indicating the child's growing understanding of gender permanence but still associating activities with certain genders.
Step-by-step explanation:
The statement "I am a girl and I will always be a girl, unless I play with a toy truck, which would make me a boy," reflects a child who is in Kohlberg's gender development stage known as the gender stability stage. This is a part of his cognitive developmental theory where children around the age of 5 to 7 start understanding the permanence of their gender. However, they may still associate certain activities, behaviors, or objects (such as the toy truck) with one gender and believe that engaging in these can change their gender. It is important to recognize that play activities and toys do not determine a child's gender and such beliefs are typically outgrown as children's cognitive abilities develop further. The understanding that gender identity is consistent regardless of activities or preferences is part of a child's cognitive and social development, reflecting a more mature stage in Kohlberg's model.