J.L.Lemke On-line Office

 Index to 'Across the Scales of  Time'

Activity in Time 

Imagine a school classroom at work. What’s happening? What are the characteristic timescales of the processes and events that make it ‘a classroom’ for us? Almost certainly people are talking, and their actions, whether producing an utterance or writing at the chalkboard or handing someone a scissors, cannot be understood, either as a selection from the available repertory of human actions or in terms of timing and sequence (what next? what, when?), apart from the meanings being made in talk and other forms of action (for detailed descriptions and analyses of the particular classroom scenes I have in mind as I write, see Lemke 1995, 1996, in press; Kamen et al. 1997; Roth 1998). 

What are the characteristic timescales of the actions, processes, and events we observe? Our immediate human interactional timescale ranges from the glance and the word, said or done in a second or less, to the complex sentence spoken or heard, the complex action performed over a few tens of seconds. Evolution has tuned us to this narrow range of timescales; our survival has depended for hundreds of millennia on noticing brief events (a glimpse of predator through the brush) and sustaining short-term cooperative action. But in the classroom, if we watch and listen long enough, we begin to find repeating patterns (e.g. Mehan 1979, Lemke 1990): individual utterances of certain semantic types (questions, answers, evaluations of answers) predictably follow one another to constitute an exchange. There are identifiable types of exchanges. These recur, recognizably for us and for the participants, not just for a while, or among the same participants, but on different days, in different situations, and even in different classrooms in different schools. They constitute a cultural pattern or social semiotic formation (cf. Lemke 1995). Exchanges also enter into patterns on a still longer timescale; the ebb and flow of talk, the shifts of topic and activity, divide the lesson into episodes. Some types of episodes also recur. Episodes get integrated somehow into lessons, and there are also lesson types, and even sequences of lesson types (cf. Christie 19.. on ‘curriculum genres’) that recur across wide geographical areas and  which may take days or weeks to complete. At these longer timescales there are curriculum units and months- to years-long integrated curricula. 

What about shorter timescales? Even an utterance of a single word consists of recognizable and repeated sound patterns, the articulation of the distinctive phonemes of a language, recognizable and repeatable, though perhaps at the edge of our normal awareness. A typical English vowel or short syllable takes about one-tenth of a second to articulate. These articulations represent coordinations of fine muscle control by neuron impulses acting at the few to tens of milliseconds scale, and they in turn sum over neuron membrane depolarizations and ion and neurotransmitter flows that occur on the millisecond timescale. Below that are still faster biochemical reactions, but the scale of the fastest human actions is basically set by the millisecond scale of neuron processes. No coordinated human action, not even autonomic reflexes, can happen faster. 

Table 1 shows the approximate timescales for each order of magnitude above and below the 1 second focal scale of human action. At each timescale we can recognize characteristic processes and social practices. For adjacent timescales it is also quite clear that the processes at the next lower timescale make possible the repeatable patternings of the next longer scale, in accord with the reductionist model of systems hierarchies. What is equally important, however, is that there is always also a higher level process already in place, already running on its own longer timescale, and this sets the context which constrains what is likely and what is socially appropriate at the next scale below. A student’s answer to a teacher’s question is also meaningful for the participants as part of an exchange, not just as an utterance in its own right, and is judged as appropriate or not to the on-going exchange, and to the episode, the lesson, the unit, the curriculum … and many higher-level contexts. These contexts however are not static, they are themselves processes unfolding in time. Very slow processes function like constant, static backgrounds on the timescale of much faster processes.   

TABLE: Timescales for Human Activity


Chemical synthesis



Neurotransmitter synthesis

Membrane process



Ligand binding

Neural firings



Neuron process

Neuronal patterns



Multi-neuron process

Vocal articulation



Edge of awareness


1-10 seconds


Word, holophrase, short monologue; in context


2- 102

Seconds to minutes

Dialogue; interpersonal relations ; developing situation



o(15 minutes)

Thematic, functional unit; speech genre, educative


103 – 104


Curriculum genre

Lesson sequence


o(2.75 hours)

Macro curriculum genre

School day



[“seamless day”]



11.5 days

Thematic, functional unit

Unit sequence




Semester/ Yr Curriculum


4 Months

Organizational level; unit in next scale

Multi-year Curriculum


o(3.2 years)

Organizational level; limit of institutional planning

Lifespan Educational Development


o(32 years)

Biographical timescale;

Identity change

Educational system change


o(320 years)

Historical timescale;

New institutions

 Note: o(time) means times on the order of magnitude of ...

Worldsystem change


3200 years

New cultures, languages; limit of historical records

Ecosystem, climate change


32,000 years




320,000 years

Last ice age

Evolutionary change


3.2 million years

Scale of human evolution



32 million years




317 million years


Planetary change


3.2 billion years

Origin of life, of planet

Universal change


32 billion years

Cosmological processes


It is useful to analyze scale hierarchies in groups of three levels at once (cf. Salthe 1985, 1993; Lemke 1995, in press-b). Call the middle level of any such group the focal level, or level N, the focus of our interest for now. Dynamical systems theory basically says that processes (and participants in those processes) can only interact directly and exchange significant amounts of energy or information if they are on  the same scale. Technically this is only exactly true if we mean on the same time scale (see discussion of the adiabatic principle below). What is possible on the focal scale, the kinds of interactions that can happen, depends on the kinds of processes and participants at the level immediately below, level N-1. Processes at level N-1 are constitutive of processes at level N; they provide the affordances for activity at level N. But level N is never the top level (certainly for human social processes); interactions on the focal level are not free to range over all the possibilities afforded them: they are also constrained by being themselves part of longer timescale processes at level N+1. The longer-scale processes determine what is probable at the focal level. There are always many ways in which the interactions at level N can satisfy the constraints of level N+1, but the probability of each path depends in part on whether it is consistent with the emerging patterns at level N+1. 

It helps in understanding these inter-level relationships to think of their history and origin. As interactions at some timescale become linked, or coupled, and thus more interdependent, as they do in complex systems of the kind we are interested in here, there are fewer and fewer possible self-consistent patterns (cf. Kaufman 1993). In the origin of life, for example, there were originally a lot of protein or RNA-like molecules mutually catalyzing one another’s synthesis. As more new molecules were produced that could function as potential catalysts for still more chemical reactions, eventually a condition was reached where a few sequences of reactions formed a self-sustaining cycle that then rapidly outpaced other reactions and entrained most of the available nutrients into its own on-going patterns. The new patterns were emergent, essentially allowed by the previous chemistry but not required by it, and so unpredictable. The new cycles take more time, complete on a longer timescale than the individual constituent reactions. They form a new level of organization. From now on, any fluctuations in the concentrations of chemicals in the pool are buffered by the existence of the new cycles, and information which takes this form only reaches some still longer-scale (N+1) process after being filtered or buffered by the new cycles. Once in place the new cycles also alter the probability of reactions occurring on the level below them, providing downwards constraints. And of course the new level now becomes itself a potential unit of organization for something (like us) at a still higher level to be built out of. 

All new levels of organization emerge as intermediates between pre-existing levels, and profoundly change the relations among the formerly adjacent levels as well as making possible still newer emergent forms (see discussion in Lemke, in press). 

Are there emergent processes and patterns in classrooms? I think every teacher and student knows that there are. There are new routines that emerge, new social groupings and the typical interactions that sustain them, class in-jokes, informal rituals, typical sayings and phrasings, favorite word usages with special meanings, etc. These in turn can become the raw material for more complex new patterns unique to the classroom, and they certainly constrain the probabilities of actions and utterances which would invoke these special meanings or contribute positively or negatively to social relationships. A classroom, and indeed every human community, is an individual at its own scale of organization. It has a unique historical trajectory, a unique development through time. But like every such individual on every scale, it is also in some respects typical of its kind. That typicality reflects its participation in still larger-scale, longer term, more slowly changing processes, which shape not only its development but also that of others of its type. 

A classroom community can be taken as a whole on its longest timescale of activity, typically a few months to a year. We can ask how it develops, as an individual and as a typical instance of its kind. Subject to what constraints from which still larger-scale processes? Made possible by which characteristics of which shorter timescale processes? We can look at its component processes and constitutive units as well, each on their own timescales. And here things begin to get rather complex, because we can easily see that, for example, a social grouping may form that lasts longer than the classroom community. Is it a unit within the classroom community, or a unit at a higher scale? What about a textbook? It is surely the product of a larger-scale, longer-term process (of writing, editing, publishing, etc.), and so a participant in processes on those scales, but it also seems to be a small-scale participant in short-term events within the classroom (e.g. reading aloud a homework problem at the end of a chapter). To understand such phenomena we need to understand the two different principles that seem to govern relationships across scales: the adiabatic principle, and the principle of semiotically mediated heterochrony.