The internal/external attention framework characterises attention focused on internal representations, such as emotions, versus external representations, such as perceptual stimuli. The inability to focus one's attention is considered a critical factor in psychiatric disorders. While these different attentional foci are likely generated by the dynamic interplay of multiple cognitive processes, previous studies have generally examined single cognitive dimensions. We developed a new method, cognitive dynamic similarity analysis (C-DSA), to clarify how cognitive processes differ between experimental conditions. In an MR scanner, participants performed a word-processing task in which they focused on either their own emotions or the number of letters associated with a stimulus. To extract cognitive dynamics at the single-trial level, we applied cognitive dynamics estimation, a recently developed method that generates whole-brain activation maps for four cognitive dimensions (emotion processing, selective attention, self-referential thought, and working memory) using a meta-analytic platform. We then performed C-DSA to calculate the difference between internal and external attention for each cognitive dimension. C-DSA revealed significant differences between internal/external attention in all cognitive dimensions, but especially in emotion processing. Moreover, the difference between attention conditions of selective attention was negatively associated with the severity of depression and state-anxiety, but positively associated with trait-anxiety. Our findings suggest that C-DSA applies to both naturalistic and controlled dynamic processes and may be valuable in clinical settings by linking dynamic cognitive mechanisms with issues like ageing and psychiatric disorders.