This phenomenon has been studied in various studies, involving both students and full-time employees. The results showed that the awareness of working outside of standard working hours has a negative impact on intrinsic motivation. This effect occurred regardless of whether participants were explicitly reminded that they were working outside of normal working hours.
An important factor contributing to this undermining of intrinsic motivation is the social norm. People are social beings and tend to synchronize their schedules with those of others. When someone works outside of standard working hours, this can lead to a feeling of isolation and the idea that they are not in line with the rest of society. This can result in an increased awareness of alternative, possibly more satisfying ways to spend time, such as social activities or relaxation.