briefly examined is the brain on tags

Tags might serve an additional benefit beyond increased access to resources. The cognitive demands of picking an ontological category for an item versus merely giving it a label might be quite different from one another. Gao, replicating elements of an earlier study, confirmed that participants reported exerting more cognitive effort with maintaining a hierarchy for organization as opposed to categorizing documents into multiple groups with tags (824). However, participants also seemed to prefer hierarchal organizational schemes to tags, if for no other reason than as a visual marker (825). The second part of the study found that cloud tags that weighted the frequency of terms and represented them in a larger typeface than other terms could enhance tag memory.

It is likely that image-based devices such as tag clouds use a different region of the brain than text-based ones do, which can be used to enhance cognition. Our pre-attention skills can be called into play to track information that is happening on the periphery of our environments (Ambient Devices). Tag clouds and synonymic stars can engage a different region of the brain than a hierarchical list, which probably leads to less brain fatigue.

Gao, Q. (2011). An Empirical Study of Tagging for Personal Information Organization: Performance, Workload, Memory and Consistency. International Journal of Human-Computer Interaction. 27I(9), 821-863.