Nine-year old Sofia was excited about having a new baby brother. However, she wa

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Sofia’s new thumb-sucking behavior could be explained by the defense mechanism of regression. Regression is a defense mechanism that involves returning to an earlier stage of development when faced with stress. In this case, Sofia may be feeling stressed by the arrival of her new baby brother and has regressed to a behavior that she used to do when she was younger.

It is common for children to experience a range of emotions when a new sibling arrives. Some children may feel jealous or resentful towards the new baby and may act out in different ways. It is important for parents to be patient and understanding with their children during this time and to help them adjust to the changes in the family dynamic.

I hope this helps! Let me know if you have any other questions.