This basic observation has been one of the central struts of my belief system for a long time. It urges patience on us all.
The authors of this term were eminent sociologists John and Matilda Riley. They proposed that any substantial cultural event inevitably produces a structural response, but only after a variable hiatus. They made this pronouncement regarding their interest in the Aging Boom. They based their term on the fact that the emerging large cohort of older people was not being met by an appropriate administrative response; hence the term "structural lag." The Social Security System took a while to kick in.
I have used this term widely in my studies and writings. Even a knee jerk could be considered to exhibit lag as when the tendon is stretched by a thump it transfers the energy to the spinal cord where the thump initiates a neural pathway which elicits a motor contraction, a jerk, really a functional lag. To build a muscle takes time.
This functional response is a primitive exhibit of lag, but its time line is less imperative than the lag in almost all structural examples that I can nominate.
Consider Darwin's Natural Selection. It represents a structural lag in that those species that survived were those that adapted to the environmental permutation that they confronted. It takes a while for structure to capture function, i.e., evolution. It takes altered function a while to elicit reactive structural response. So the term "structure lag" is central do the whole enterprise.
Symmorphosis is a relevant term developed by Ewald Weibel in Bern. This term underlies the energetic stimulus to alter structure by epigenetic mechanisms. All relevant body structures and functions scale precisely to the stimulus. No single rate limiting step is allowed. No bottlenecks in Nature.
The entire proposition of "use it or lose it" exhibits structural lag. If I desire to build up my muscles I must embrace a strengthening protocol. I must inject enough challenge to the situation that the DNA of the muscle can build a new architecture, and I must keep it up. The muscle shrivels abruptly when disused. The muscle becomes what it does, or doesn't.
Practice make perfect. Every part of us obeys this rule. The part of the brain that represents the left hand of the violinist bulges. The parts of Einstein's brain that were involved in his creative genius showed similar plasticity. But it took time. All learning exhibits structural lag.
It is in the social domain that the term has the most pressing relevance. My dear friend John Gardner was fond of observing "he who would change the social norm cannot be of short wind." This caution has served me admirably. Numerous times when my impetuousness demanded an immediate confirmation of what I had presumed to be an obvious truth, but clearly was not obvious to my contact. I flustered, "Why don't you get it?"
Patience is a quality that I, and most others, have in clearly limited amounts. Instant gratification is inconsistent with structural lag. We want what we want now, no excuses allowed. Incrementalism is an alien thought.
Any reflection indicates that time moves slowly. "Take your time" is a perpetual advisory. Recognition of structural lag serves us all in our enterprises.
Structure recapitulates function: But it takes time to do so.
"It is never too late to start."