An important contribution to the anthropology of time and material culture studies, this volume takes as its primary point of departure that the mechanisms for “telling” time (the author focuses on clocks and calendars) are engaged in shaping our experience and subsequent enactment of temporal realities as much as they are nominally thought of as representing them. Accordingly, the history of clocks, their continuous improvements and our obsessive tweaking for accuracy is a history—cultural, social, and, finally, colonial—of “artifactually mediated cognition.” Objects of Time is indeed a work in cognitive anthropology (it appears in the book series of the Society of Psychological Anthropology), but it makes a point of anchoring the cognitive modeling in real world processes. The argument in support of artifactual relativism, the stronger version of the Sapir-Whorf hypothesis, is based on the claim that material extensions of cognition are similar to language in that they mediate between the mind and reality but, unlike the purposeful generative function of language, come already sedimented as complete artifacts of understanding that do not combine into higher units or are able to function self-reflexively (metalinguistically). If anything, as David Miller notes, they “work by being invisible and unremarked upon” (p. 19). The implications are essential to the argument that is developed throughout the several thematic chapters: our understanding of this interplay between cognitive artifacts and user cognition must incorporate the social life of these artifacts as commodities (here Marx augments Sapir-Whorf) that work their ways across space and time in a cross-cultural and transhistorical process. Birth makes good use of Adam's concept of “timescapes” to think critically of studies that have ascribed a particular sense of time to specific societies (Bourdieu's “Kabyle time” or “Nuer time” of Evans Pritchard come to mind) by emphasizing a society's framework of reckoning time and dates as a hybrid system that incorporates multiple devices and frames with differing origins, functions, and symbolic values oftentimes mutually incommensurable and, yet, coexisting in ways that are themselves revealing. It is because these mind extenders are artifacts that they are able to serve their purpose, embody the history of their design but also hide it. Fortunately, the sense of mental indigestion caused by reading this mostly overstuffed book of major and minor points is greatly relieved when the author's exposition calms down and he takes the time to present richly detailed historical and ethnographic case studies; the best come from his own work in Trinidad. We get to appreciate how Christian, Hindu, and Muslim calendars are incorporated yet also subsumed such that the Christian structure has the historical (postcolonial) upper hand while the latter two were made to fit within it. As for our clocks—mechanisms that defer to other more authoritative clocks for accuracy—Birth points to the discrepancy between the imposed time frame that governs our behavior and the timing of activities that may itself follow another order altogether (such as biological or astronomical phenomena).

Birth makes much of the necromancy of clocks and calendars, devices that think for us while imposing on the present the mechanisms and rules of measurement decided by others at other times and in other places (although much the same holds for most institutionalizing norms). The examples from the European Middle Ages illustrate the complex amalgamation and often difficult coexistence of different temporal schemata. And the gradual fusion of two distinct cognitive tasks—measuring duration and determining the time of day—into one “clock time,” and the concomitant erosion of our ability to “tell time” by direct observation of natural and, finally, social phenomena, reminds us of the degree to which a unifying grid now orders how and what we perceive and enact “as passing.”

This line of argument is further pursued in the two concluding chapters that explore the globalizing effect of uniform time and calendar grids on time-space compression. Chapter 5 takes a closer look at how the logic embedded in the cognitive artifacts “gets embodied and creates physiological arrhythmias” that have led to a systemic reimagining and controlling of both the Earth's natural cycles and of our own bodies while continuing the growing disconnect between the particular synchronicities of these natural worlds and the new logic that subsumes and harnesses them (with work schedules, medication, etc.) unequally, resulting in embodied contradictions and social conflicts. The author's critical tone culminates with a discussion of “Creeping Cognitive Homochronicity” (a suggestive title for the final chapter), of the globally ubiquitous cognitive tools that are self-referential and not of our own making; “we must pause to reflect on the delicate balance between tools that extend and empower the mind, and tools that constrain it” (p. 171).

Not all is lost, however. Chapter 4 stands out as the more interesting for its contribution to our understanding of the in situ negotiation of coexisting temporalities or “polyrhythmia,” in effect the micropolitical strategies that are assumed by individual social actors in the mundane, everyday world. In other words, local temporalities must be understood as the coexistence of a variety of cues, based in a system of local knowledge, with the seemingly well-integrated clock and calendar times. If anything, the latter are continuously manipulated against contingencies and anticipatory signals through multiple rhythms that speak to a complex web of social actions, needs, and expectations. The author is right to draw our attention to the simplistic identification of modernity or postmodernity with general shifts in uniform temporalities. E. P. Thompson's work on time and labor, Michael Foucault's on discipline, and Benedict Anderson's notion of “homogeneous empty time” are the best known and widely used concepts “that do not capture the diversity of thoughts about time that one can find ethnographically” (p. 118) and, one may add, that would help us better understand both forms of resistance against dominant time grids but also our own, present-day concerns with the impact of IT on social action as well as cognitive dissonance.