Passage Summary: While we usually think of the five senses as totally separate, some people experience them bleeding into one another, leading researchers to believe their sensory boundaries are blurred.

Conclusion: The experiences of synesthesiacs demonstrate that their senses do not follow the standard boundaries that typically separate the five senses.

Reasoning: Some individuals report sensory overlaps, such as perceiving colors as having smells or tasting a specific color when eating certain foods.

Analysis: To weaken this argument, we need to find a reason why these 'cross-sensory' reports don't actually prove the senses are overlapping. The argument assumes that if someone says they 'taste blue,' it is a literal sensory crossover rather than a psychological association or a linguistic quirk. Look for an answer that suggests these experiences are caused by something other than a breakdown of sensory boundaries, such as a memory-based association or a non-sensory neurological glitch. If the 'blue' taste is just a learned reaction, the 'boundary' between the physical senses might still be perfectly intact.