Source information is inherently linked to working memory representation for auditory but not for visual stimuli

Failing to remember the source of retrievable information is known as source amnesia. This phenomenon has been extensively investigated in long-term memory but rarely in working memory, as we share the intuition that the source information of an item that we have encountered in the immediate past is always available. However, a recent study (Chen, Carlson, & Wyble, 2018) challenged this common sense by showing the source amnesia for simple visual stimuli (e.g., colored square) in the context of working memory when participants did not expect having to report source information, which indicated that the source information of visual stimuli was not automatically encoded into working memory. The current study sought to further examine this newly discovered phenomenon by testing whether it persists with complex and meaningful stimuli in the visual modality (Experiments 1, 4a & 4b), cross-visual-and-auditory modalities (Experiments 2a & 2b), and within-auditory modality (Experiment 3). Interestingly, the results revealed that short-term source amnesia was a robust effect in the visual modality even for complex and meaningful stimuli, whereas it was absent in the cross-visual-and-auditory or within-auditory modalities, regardless of reporting expectation. This indicates differences in working memory representations of visual and auditory stimuli, namely, the representation of auditory stimuli was stored together with the corresponding original sources, while that of visual stimuli was stored independently of its source information. These findings have crucial implications for further clarifying the longstanding debate regarding whether or not there is a modality-independent working memory storage system for different modalities.