mrs. ota is a 72-year-old woman whose recent fall resulted in a femoral head fracture. in the days since her subsequent hip surgery, she has been experiencing intermittent pain and requested breakthrough analgesia several times over the past 24 hours. however, her son and daughter-in-law came to visit for the first time 2 hours ago, and mrs. ota has denied pain during this time period. the nurse recognizes that mrs. ota may be experiencing less pain at this time because: