Passage Summary: Since even tiny babies prefer the same musical notes that are popular all over the world, it's probably something we're born with rather than something we learn.

Conclusion: Humans likely have an innate, biological predisposition for certain musical intervals.

Reasoning: Six-month-old babies showed more interest in specific intervals that are also common across global musical cultures.

Analysis: To strengthen this, we need to rule out the possibility that the babies learned this preference in their first six months of life. If the babies had already been exposed to these common intervals through their environment, the 'biological' conclusion would be much weaker. Look for an answer that suggests these preferences are present before significant cultural conditioning can occur or that the babies in the study had no prior exposure to those sounds.