Why Do Regular and Reversed Items Load on Separate Factors? Response Difficulty vs. Item Extremity

When constructing measurement scales, regular and reversed items are often used (e.g., "I am satisfied with my job"/"I am not satisfied with my job"). Some methodologists recommend excluding reversed items because they are more difficult to understand and therefore engender a second, artificial factor distinct from the regular-item factor. The current study compares two explanations for why a construct's dimensionality may become distorted: response difficulty and item extremity. Two types of reversed items were created: negation items ("The conditions of my life are not good") and polar opposites ("The conditions of my life are bad"), with the former type having higher response difficulty. When extreme wording was used (e.g., "excellent/terrible" instead of "good/bad"), negation items did not load on a factor distinct from regular items, but polar opposites did. Results thus support item extremity over response difficulty as an explanation for dimensionality distortion. Given that scale developers seldom check for extremity, it is unsurprising that regular and polar opposite items often load on distinct factors.