Complex sentence: These results suggest that dominant individuals experience higher cortisol levels as well as higher growth rates, since higher cortisol levels in the blood indicate that an individual either has less stress or better internal control when stressed.
Split into simpler sentences: These results suggest that dominant individuals experience higher cortisol levels as well as higher growth rates. This makes sense because higher cortisol levels in the blood indicate that an individual either has less stress or better internal control when stressed.