Principal Findings
This 5-week longitudinal field experiment examined the effects of wearable fitness tracker feedback on AAM. In addition, it explored the effects of AAMs on health and well-being and several affective and behavioral determinants of health. Finally, this research developed and tested a transparent, scalable meta-mindset intervention that empowers individuals to adopt beneficial activity mindsets deliberately.The results showed that simply receiving accurate step count feedback led to improvements in participants’ AAMs, helping them realize that they were engaging in more health-promoting physical activity than they had previously believed. (However, note that participants in our sample were relatively active, with an average of 7066 steps per day at baseline compared with the US average of 4774 steps [Experimentally deflating participants’ step counts by 40% led them to adopt more inadequate activity mindsets. Compared with participants receiving accurate feedback, those receiving deflated feedback adopted an unhealthier diet and felt negative affect more frequently. They also experienced declines in mental health and self-esteem and increases in resting HR and blood pressure. Finally, participants who received the meta-mindset intervention (in addition to accurate step count feedback) adopted more adequate activity mindsets and had improvements in affective experiences and functional health compared with participants receiving accurate feedback only.Interestingly, the step count displayed by the wearable tracker appeared not to influence engagement in physical activity (in line with other research showing inconsistent or null effects of wearables and smartphone apps) [