- Based on empirical evidence, acquired in two experiments, we argue in this position paper that cognitive biases play a role in software engineering. Our research has targeted mainly the problem of over-requirement, which refers to specifying a system beyond the actual needs of the customer. The results of our experiments have demonstrated the impact of four cognitive biases in the context of software development, showing their connection to over-requirement, as well as over-scoping and time-underestimation. We further argue that accounting for cognitive biases in the software development context is not enough and that it is important, in both the practice and research arenas, to investigate solutions that already proved effective in reducing cognitive biases in other contexts. This paper contributes to a better understanding of some of the cognitive processes underlying software engineering, focusing on improvement of software development activities toward better performance and higher quality.