The researchers developed a new method called Profile Repeatability (PR) to evaluate how consistent individual hormone response profiles are over time. This method considers the shape of the response curve, not just individual points. They tested this method using synthetic data and real data on stress responses in European starlings. The PR scores were sensitive to changes in the number of time points and replicates, showing that individual repeatability can vary. Human observers had different perceptions of repeatability compared to the PR scores, suggesting they may underestimate repeatability when response profiles cross each other. Overall, the PR method provides a more accurate assessment of individual repeatability compared to traditional methods.