What is it about the teaching-research nexus that inspires engineering undergraduates to want more and become researchers themselves? In this study, we sought to discover more about the influences on current PhD students' choices to embark on higher degrees by research in various fields in engineering in an Australian research-intensive university. An online survey and follow-up focus group discussion revealed that these students are driven primarily by a genuine interest in research itself, rather than other factors such as career advancement (although this too, plays a role). While this is not particularly surprising, what did become apparent was the specific undergraduate experiences that most strongly influenced their decision to undertake research degrees, including enjoying doing project-based work, being exposed to lecturers who were passionate about their own research, and working on a vacation research scholarship. Further analysis reveals that the weighting of various influences changes according to whether the students are local Australian graduates or international PhD candidates. (Contains 2 tables and 3 figures.)