currently are only accessible through self-reports. New techniques such as the
measurement of Cycling Alternating Pattern are improving objective sleep quality
measurement (Rudzik and Ball 2016 ).
Across the Lifespan
The timing of when experiences occur across the life span has great importance.
Research is making clear that early developmental experiences are particularly
significant, with these experiences shaping the physiology and behavior of indi-
viduals for the rest of their lives. This understanding of the critical importance of
early life experiences has led to the concept of biological imbedding (Pike 2016 ).
Exposure to stress early in the lifespan, particularly due to malnutrition, can lead to
a“thrifty phenotype”, when those born small encounter an environment of plenty.
Early stress coupled with a later wealth of resources puts individuals at great risk for
obesity, type 2 diabetes, and heart disease later in life (Barker et al. 1993 ; Hales and
Barker 2001 ). Prenatal stress is made visible in birthweight and by later health risks.
In neonatal growth, the undeveloped communication skills of the infant make
self-reports of the growth experience problematic (Lampl et al. 2016 ). Behavioral
manifestations of growth, such as fussiness, are consequentlyfiltered through
parental reports. In somewhat older children, reports of“growing pains”and irri-
tability are indicative of the growth experience, but there is much research needed
in order to link objective growth measures with pain experience and behavioral
changes. As noted, puberty is a time when major reorganization of the neurological
system takes place, with associated changes in behavior and emotional experience
(Steinberg 2005 ); puberty is also a time of accelerated physical growth. Although
we may think of infant and adolescent growth as obviously visible, Lampl has
shown that much about the exact nature of growth is still invisible to the eye.
Similarly, children’s physical activity is largely taken for granted and most of the
time takes place in contexts not ordinarily observed by adults. In some instances,
the activities are not really considered a“physical activity”per se, but chores that
simply must be done. Physical activity in young children can be based on subjective
reports,filtered through parents, or measured with accelerometers (Malina et al.
2016 ). However, none of these measures may provide an understanding of the
context of that activity, which could give clues to how more physical activity can be
encouraged. Correlations between self-reports and objective measures of activity in
children and adolescents have not been strong (Brener et al. 2003 ).
Other experiences are mainly confined to late stages of the life span. For
instance, bone health, specifically reductions in bone density that increase during
the menopausal transition and potentially result in osteoporosis, is largely invisible
until bone loss leads to pathologies such as fractures. Subjective reports by women
about their bone health, e.g., Vitamin D levels, have not been concordant with
6 D.E. Brown and L.L. Sievert