Thanks Dr. Browndyke, that helps a lot!

I have a follow-up question. For the same contrast above, I got a result that has significant p-value (p>0.05) for connectivity-score but the beta/effect size is -0. I don't understand how can the beta/effect size both be 0 and significant? I have attached the screenshot of the results.

For information on my study, I am testing for association between functional connectivity and reaction time (RT) scores in individuals with (DYS) and without dyslexia(CONTROL). For this contrast, I selected CONTROL, DYS, RT_SCORES_CONTROL, RT_SCORES_DYS and did 0, 0, 1, -1. 

Thank you!