Several research efforts to investigate the correlation between thermal comfort conditions and human performance and learning are summarized. Because the results are controversial, several problems and hypotheses about the general field will be offered first.

It is an accepted fact that people prefer thermal comfort. The generally accepted hypothesis is that they will also perform better, when comfortable, whatever they are normally requested to do. However, the data are so varied that they invalidate any solid conclusions that performance changes significantly before either cold or hot discomfort occurs. These levels of discomfort are beyond what people are likely to accept for other reasons, so the hypothesis that comfortable conditions maximize performance cannot be supported.

These hypothesized illustrations cannot be taken as hard conclusions, but only as representative of the problems. Why is this? Common sense judgment indicates that reducing stresses (thermal stress is only one) should enable a person to direct attention (mental and physical) on activities of his choice, and therefore to perform better. This should follow in day-to-day activities involving work performance, learning efficiency, or leisure pursuits.

A reasonable hypothesis which explains the elusiveness of proof of this proposition is that inter- and intra-individual differences in human motivation to perform can vary over far greater magnitudes than the performance variations caused by the experimental stresses employed. It is well known that, when life or fortune is at stake, performance can be almost Herculean, with almost total disregard for severe environmental stresses (e.g., soldiers during battle).

Several studies have been selected to illustrate the very extensive work done in the field. Efforts in the areas of industrial production and military performance are recognized but not covered here due to space limitations.