To date, cyber security research is built on observational studies involving macro-level attributes as causal factors that account for state behaviour in cyberspace. While this tradition resulted in significant findings, it abstracts the importance of individual decision-makers. Specifically, these studies have yet to provide an account as to why states fail to integrate available information resulting in suboptimal judgements such as the misattribution of cyber operations. Using a series of vignette experiments, the study demonstrates that cognitive heuristics and motivated reasoning play a crucial role in the formation of judgements vis-à-vis cyberspace. While this phenomenon is frequently studied relative to the physical domain, it remains relatively unexplored in the context of cyberspace. Consequently, this study extends the existing literature by highlighting the importance of micro-level attributes in interstate cyber interactions.