The Rummer et al. (2014) study demonstrated that the sound is associated with a positive mood. Specifically, the study found that subjects in a positive mood tend to invent words with /i:/, whereas when in a negative mood they tend to invent more words with /o:/. The study also identified the relationship between vowel identity and emotional state, in that a subject's positive mood made them tend to produce more words containing /i:/, and a negative mood made them produce more words containing /o:/. These findings suggest that there is a link between the sounds we make and the emotions we experience.