Challenging dual-coding theory: Picture superiority effects persist in aphantasia

Abstract

Dual-coding theory proposes that superior memory for pictures compared to words (picture superiority effect) and concrete words compared to abstract words (concreteness effect) stems from the ability to store information in both verbal and image codes. According to the theory, having two distinct memory codes available during retrieval increases performance because either code can independently lead to successful recall, and one code can serve to cue the other. For example, when recalling an image of a dog, one can retrieve the verbal code (‘dog’), or they can first retrieve the mental imagery of the previously seen dog which then affords the verbal code to recall. The current study tests this theoretical explanation by examining recall performance in individuals with aphantasia—the inability to voluntarily generate mental imagery. Based on dual-coding theory, aphantasic individuals should show neither the picture superiority effect nor the concreteness effect due to their inability to generate mental images as retrieval cues on a recall memory test. We compared recall performance between aphantasic and typical imagers across four stimulus types: pictures, symbols, concrete words, and abstract words. Despite their imagery deficit, aphantasic individuals still demonstrated better recall performance for both pictures and symbols compared to words. Moreover, while typical populations show similar recall for pictures and symbols, aphantasic individuals displayed superior recall for symbols compared to pictures, possibly reflecting their alternative cognitive strategies that particularly benefit symbol processing. The persistence of better recall performance for both pictures and symbols in aphantasia suggests that there are memory mechanisms beyond dual-coding that drive these effects, or that dual-coding theory requires significant modification. This study provides novel insights into the relation between mental imagery and memory, challenging traditional theoretical frameworks and suggesting the need for alternative explanations of these well-established memory phenomena.

Challenging dual-coding theory: Picture superiority effects persist in aphantasia

Abstract

Dual-coding theory proposes that superior memory for pictures compared to words (picture superiority effect) and concrete words compared to abstract words (concreteness effect) stems from the ability to store information in both verbal and image codes. According to the theory, having two distinct memory codes available during retrieval increases performance because either code can independently lead to successful recall, and one code can serve to cue the other. For example, when recalling an image of a dog, one can retrieve the verbal code (‘dog’), or they can first retrieve the mental imagery of the previously seen dog which then affords the verbal code to recall. The current study tests this theoretical explanation by examining recall performance in individuals with aphantasia—the inability to voluntarily generate mental imagery. Based on dual-coding theory, aphantasic individuals should show neither the picture superiority effect nor the concreteness effect due to their inability to generate mental images as retrieval cues on a recall memory test. We compared recall performance between aphantasic and typical imagers across four stimulus types: pictures, symbols, concrete words, and abstract words. Despite their imagery deficit, aphantasic individuals still demonstrated better recall performance for both pictures and symbols compared to words. Moreover, while typical populations show similar recall for pictures and symbols, aphantasic individuals displayed superior recall for symbols compared to pictures, possibly reflecting their alternative cognitive strategies that particularly benefit symbol processing. The persistence of better recall performance for both pictures and symbols in aphantasia suggests that there are memory mechanisms beyond dual-coding that drive these effects, or that dual-coding theory requires significant modification. This study provides novel insights into the relation between mental imagery and memory, challenging traditional theoretical frameworks and suggesting the need for alternative explanations of these well-established memory phenomena.