Read the following case study and answer the proposed question:

Emily was hiking with her dog when another dog attacked her and bit her wrist. She was terrified. The wound became badly infected and very painful, requiring medical treatment. On another occasion, her sister, Marian, was walking in a field when three large, growling dogs chased her. The dogs' owner heard the commotion and intervened before she was physically injured. Marian developed a fear of dogs - she became fearful of visiting friends who have dogs or participating in leisure activities where dogs might be present. In contrast, Emily, who suffered painful injuries, did not develop a fear of dogs.

What could account for these differences in reactions between the sisters?