Both monkeys were deprived of foood. While both were deprived of any nutrition, one was fed a non-nutritive flavored placebo. That monkey did not secrete glucocorticoids. The other did. The critical factor seems to be that the first monkey did not perceive things to be as stressful as the second one.
Most scientists now accept the power of psychological variables to modulate stress physiology.
Lack of control, lack of predictability, and lack of outlets for frustration. Rats were subjected to intermittent electric shocks. One rat could control the situation because it was able to press a lever to decrease the rate of shocks. A second rat received a shock whenever the first did, but was without control. The latter had far more glucocortiocid release.