Describe the findings of Paivio's work on the memory of concrete nouns (such as "hotel" or "garden") and abstract nouns (such as "honor" and "knowledge"). Analyze these findings in terms of the dual coding theory (the idea that concrete nouns can be represented in memory both pictorially and verbally, while abstract nouns possess only a verbal representation). How does coding in terms of verbal and visual representations explain differences in abstract versus concrete noun recall?