Existing sensors, such as those based on simple pressure switches and motor resistance, are limited in their ability to detect
subtle changes in pressure and to distinguish between different textures.
I can not do justice to Putnam's
subtle sifting of evidence and rich discussion of possible causes, but will simply report that the main culprits,
in order of importance, are: generational
change, television watching, suburbanization (with its associated increases
in sprawl and commuting time), and
pressures of time and money (including increases
in two - career families).
The scientists initially reasoned that
subtle changes in weather — atmospheric
pressure, temperature, wind speed, cloud cover, or rainfall — signaled the pending disaster.