When faced with the need to transform an object, idea, or situation, people have a tendency to favor adding new components rather than removing existing ones. This is called the "additive bias." Previous research, along with historical and anecdotal examples, shows that this bias may significantly reduce problem-solving abilities and have a detrimental impact on the innovation process. In this study, our objective was to develop a novel tool, the additive bias implicit association test (ad-IAT), to investigate the reasons underlying people's preference for additive actions. By using this tool, we empirically demonstrated that people displayed an inherent tendency to assign a positive valence to additive concepts and to perceive additive actions as safer and more functional than subtractive concepts. Importantly, we also found that implicit preference for addition resulted in participants favoring additive actions while neglecting subtractive alternatives when engaged in a problem-solving task. Collectively, our series of experiments substantiated the effectiveness of our ad-IAT in uncovering and quantifying the additive bias. This, in turn, provided a deeper comprehension of the underlying factors contributing to the bias and its impact on people's behavior.