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If the ﬂow of MWT is immutable, the human brain hardly perceives it as such. Gooddy, in his book Time and the Nervous System , distinguishes between Personal Time (PT) and Government Time (GT). The former marks the ﬂow of time (MWT) as perceived by the individual brain; the latter refers to the passage of time as measured by a collectively recognized reference clock, from the brain’s perspective an external synchronization device to MWT. Alteration in the perception of time, of the ﬂow of one’s PT, occur within the perceiving agent’s mind.
Fraisse emphasizes the necessity to separate the perception of duration, which takes place in the psychological present, and the estimation of duration which “takes place when memory is used either to associate a moment in the past with a moment in the present or to link two past event” . Memory frees the mind from the continuous, irreversible ﬂow of MWT. The mind can manipulate memories, events taken out of MWT, and place them in ﬂows of time, that extend in the past and future (including the ﬂow of MWT). Gooddy captures this ability in his observation that “the [human] brain is the place or mechanism or medium by which time is converted into space and space into time.”
Musical tasks constantly engage the ability of the brain to move information in and out of the ﬂows of times (going back and forth between time and space): memorizing a piece of music, performing it from memory, writing a piece of music as a score, performing a piece of music from a score. A musical notation system affords spatial representation of the perception of time through music; a performance is the re-creation of this perception from its spatial representation. The goal of a music notation system that effectively supports total communication between the composer and the performer remains elusive. Technology relatively recently afforded exact recording and recreation of performances. But a recording only captures one single, permanently frozen, physical manifestation of the musical material, with no place for re-creation or re-interpretation. The recording is super-naturally faithful to the performance, but does not explicitly encode, nor allows the full recovery of, the full depth of intent of the source material. Furthermore, the exactness of the reproduction is not necessarily a signiﬁcant, or desirable, feature from the listener’s point of view. The human brain is approximate; memory is event-based and selective. Each experience, each performance are different, and bring the prospect of renewed excitement to the listening brain. Successive re-experiences of a recording only remain interesting to a listener as long as she herself keeps changing from the experience.
Considerations about the nature and meaning of notation extend to the performing arts, such as dance and theater, and beyond. The thinking brain in MW ﬁnds itself in a constant struggle between the desire to stop time and the necessity to live (and experience) in the present. Bamberger has studied extensively the evolution of the spatialization (notation) of temporal patterns (rhythms) during child development. She reﬂects :
We necessarily experience the world in and through time. How and why, then, do we step off these temporal action paths to selectively and purposefully interrupt, stop, and contain the natural passage of continuous actions/events?The ability to control the ﬂow of one’s PT allows the brain to take temporal experiences out of the immutable ﬂow of MWT, contemplate or otherwise manipulate these experiences outside of MWT, and later re-create them in the ﬂow of MWT. This ability enables individuals to adapt, learn, generalize, create. Without it, symbolic thought would be impossible, or at least completely detached from, and therefore irrelevant to, life in MW.
How do we transform the elusiveness of actions that take place continuously through time, into representations that hold still to be looked at and upon which to reﬂect?
Perhaps the very notion of complexity lies in engaging the resilient paradoxes that emerge when we confront the implications of our static, discrete symbolic conventions with our immediate experience of always “going on.”
 Jeanne Bamberger. Evolving meanings: Revisiting Luria and Vygotsky. In G. O. Mazur, editor, Thirty Year Commemoration to the Life of A. R. Luria. Semenenko Foundation, New York, 2008.
 Paul Fraisse. Perception and estimation of time. Annual Review of Psychology, 35:1–36, 1984.
 William Gooddy. Time and the Nervous System. Praeger Pub, 1988.