Grammar originates in action planning, not in cognitive and sensorimotor visual systems.

While the PREDICATE(x) structure requires close coordina- tion of subject and predicate, both represented in consciousness, the cog- nitive (ventral), and sensorimotor (dorsal) pathways operate in parallel. Sensorimotor information is unconscious and can contradict cognitive spa- tial information. A more likely origin of linguistic grammar lies in the mam- malian action planning process. Neurological machinery evolved for plan- ning of action sequences becomes applied to planning communicatory sequences. It is tempting to relate ideas in linguistics with ideas in neuro- physiology, because at base much of linguistics is about the design and operation of a neurophysiological machine, in the language ar- eas of the brain. In the spirit of consilience, such efforts are nec- essary. Hurford's effort at tying together a formal logic developed within linguistics with the interactions between brain areas echoes another effort in BBS a decade ago (Landau & Jackendoff 1993). Like that effort, though, this one founders by proposing a parallel that on closer examination turns out to be illusory. The heart of Hurford's article, identifying the dorsal and ven- tral streams of visual processing with a logical PREDICATE(x) structure, misses the mark because there is a tight logical rela- tionship between subject and predicate; but information in the two visual streams can be independent and even contradictory, running in parallel to subserve different functions (Bridgeman et al. 2000; Milner & Goodale 1995). The dorsal/ventral terminology is somewhat deceptive, for some cortical areas that are anatomi- cally dorsal to the primary visual cortex are shared by both path- ways, or even belong to the "ventral" pathway. Terms that capture the contrast in the functions of the two pathways are more useful. What and where, as used by Hurford, are misleading because both pathways carry useful where information - it's just that the where information in the two pathways is sometimes contradictory. The terms cognitive and sensorimotor are preferable, as they describe the distinct functions of the pathways, whereas Milner and Goodale (1995) suggest what and how. Functional terms are preferable because they are less likely to lead to oversimplification or overinterpretation. The idea of using logical grammar notations developed within linguistics for describing information processing in the brain is a productive one that promises to enrich neuroscience. The literal application of logical structures to describe information process- ing within the two-visual-systems context, however, is wide of the mark because the linguistic structures and the logical structures of visual architecture are not parallel. Subject and predicate are both conscious in the minimal sense that one can talk about them. Their identities and relationship can be described, their application can be planned in language, and they define inseparable parts of a single linguistic act. The senso- rimotor pathway, however, can function without cognitive partic- ipation and without conscious intervention all the way from stim- ulus to response, an example of "vertical modularity" (Bridgeman 1999). Abstract: The objects of attention can be located anywhere along the causal link from the source of stimuli to the final output of the vision sys- tem. As causes, they attract and control attention, and as products, they constitute targets of analysis and explicit comments. Stimulus-driven in- dexing creates pointers that support fast and frugal cognition.