**Registration Addendum - Sequential Analysis** The study began recruiting in January of 2015, 20 months later, in September of 2016, we have recruited 97 couples, of which, 86 couples have completed the manipulation. Although interest in the study remains high, the selection criteria that we have adopted have prevented the vast majority of potential couples from participating. While not part of the original plan, we have decided to adopt a sequential analysis approach to determine if this study can be terminated before the full sample is recruited. To this end, study data will be analyzed at three specified recruitment milestones. While we budgeted for the recruitment of 150 couples, we expected that 20% of sample would leave the study before completion or otherwise fail to provide usable data, leaving an intended analyzable sample of N = 120. We propose to analyze the data now, with 72% of our intended sample (N = 86); again when we reach 86% of our intended sample (N = 103), and again, if necessary, when we eventually recruit 100% of our intended sample (N = 120). Using a linear spending function (power family function) for a two-sided analysis controlling for alpha of .05 (estimated using the alpha*t^phi function with phi = 1 found in the GroupSec package for R; see Lakens, 2016); the alpha boundaries for these three interim analyses are .036; .0241; and .0242. As there are two primary outcomes (intimacy and passion), a Holm-Bonferroni correction will also be applied. As the study has no expectations for the resulting effect size, or what a meaningful effect size might look like, we are reluctant to define a smallest effect size of interest, so we will continue to run the study until statistical significance is reached for at least one primary measure (intimacy or passion), or the desired analytic sample size (N = 120) is obtained. If statistical significance is reached for a primary outcome measure in an interim analysis, the study will be terminated early. Lakens, D. (2016). Performing High-Powered Studies Efficiently With Sequential Analyses. Unpublished manuscript. Retrieved from http://datacolada.org/wp-content/uploads/2015/12/5367-Lakens-EJSP-2014-Performing-high-power.pdf