Saltation and Stasis: a Model of Human Growth

Abstract

Human growth has been viewed as a continuous process characterized by changing velocity with age. Serial length measurements of normal infants were assessed weekly (n = 10), semiweekly (n = 18), and daily (n = 3) (19 females and 12 males) during their first 21 months. Data show that growth in length occurs by discontinuous, aperiodic saltatory spurts. These bursts were 0.5 to 2.5 centimeters in amplitude during intervals separated by no measurable growth (2 to 63 days duration). These data suggest that 90 to 95 percent of normal development during infancy is growth-free and length accretion is a distinctly saltatory process of incremental bursts punctuating background stasis.

Perception of visual-tactile colocation in the first year of life.

“…It is especially pertinent to the current investigation that these challenges posed by variations in body and limb posture are particularly complex across ontogenetic development. Not only do the relative sizes and shapes of the limbs, body, and head change rapidly even from day to day (Lampl, Veldhuis, & Johnson, 1992) but, additionally, the number and variety of postural changes which an infant can readily and spontaneously execute become increasingly complex with age (e.g., Van Hof et al, 2002). …”

Life history theory and the immune system: Steps toward a human ecological immunology

“…Through precise, daily measurement of infant length, linear growth has been reconceptualized as a saltatory process with periods of stasis punctuated by discrete growth episodes (Hermanussen, 1998;Lampl et al, 1992). Based on the allocation rule, one might expect an increased frequency of illness following a growth event, as this represents a significant short-term shift in resources toward growth, possibly at a cost to immunity.…”

Letter to the editors

“…As originally published, saltatory growth is a two-phase process characterized by short time duration growth events (within a period as short as 24 hours) accompanied by longer refractory intervals, or stasis (Lampl et al 1992). These two processes act sequentially.…”

“…This approach contains the following errors: empirical data derived from the saltation and stasis model (Lampl, Veldhuis and Johnson 1992) do not have to yield a predictable bimodal frequency distribution of increments. Instead, they can yield a non-Gaussian density function compatible with one distribution centred about zero and multiple distributions best described as a skewed right shoulder (figure 1).…”

“…This density function reflects the fact that saltatory growth occurs by aperiodic saltations of non-uniform amplitude and of unequal frequency, two features not accounted for by the bimodality assumption. A comparison between the data for infants (Lampl et al 1992, Lampl 1993 and the data for older children (Hermanussen and Geiger-Benoit 1995) (figure 1) is notable for two features: (a) the error of the latter study is about twice the former, illustrated by the half-width at half-height of the major distribution--this results in a wider spread of the distribution function overall; (b) the data of Hermanussen and Geiger-Benoit represent a wide range of children's ages, all older subjects than the infants studied in the sample of Lampl et al (1992). The implicit assumption in the recent publication is that the average amplitude and timing of growth saltations of a small group of American infants are applicable to children of older ages.…”