Even though existing heuristics and specification-based techniques support composing design models, it is still considered a time-consuming and highly intensive task. In addition, there is a lack of studies exploring the effects of composition techniques on software developers' affective state and development effort. This study reports a pilot study to investigate these effects while developers apply composition techniques to detect and resolve inconsistencies in output-composed models. In this sense, a widely known wearable EEG headset, namely Emotiv EPOC, with 14 channels was used, while developers made use of heuristic-based and specification-based composition techniques to evolve design models. Our results suggest that using heuristic-based techniques produced a higher effect on the developers' affectivity, compared to specification-based techniques. Moreover, the higher the effects on the developers' affectivity, the higher the odds to invest less effort and produce correctly composed design models.