How would you interpret a double dissociation between a patient who has intact language but poor visuospatial copying versus another with intact visuospatial copying but poor language naming?

• A. The pattern supports separate, domain-specific impairments in language and visuospatial function.
• B. The pattern suggests a global cognitive decline.
• C. The pattern indicates both tasks rely on the same cognitive resource.
• D. The pattern implies memory is driving both tasks.

Answer: (A)

A double dissociation shows that two cognitive abilities can function independently because they rely on separate brain systems and processes. In this scenario one patient can name objects and use language normally but has trouble copying or understanding visuospatial relations, while the other can copy visuospatially with intact perception but struggles with naming. This pattern indicates that language and visuospatial skills are supported by different neural circuits and are not just different ways of measuring the same underlying resource.

If the pattern were due to global cognitive decline, you’d expect widespread impairment across many domains rather than selective preservation of language in the visuospatial-impaired patient and vice versa. If both tasks depended on the same cognitive resource, the impairments would tend to co-vary across individuals rather than appear in opposite directions. Memory driving both tasks doesn’t fit either, since these tasks rely more on real-time processing and retrieval tied to specific domains (language vs visuospatial), not a single memory system.

So the best interpretation is that language and visuospatial abilities are domain-specific and can be selectively impaired, which is exactly what the double dissociation demonstrates.