There are also worries about the canal being unprotected by United States troops, admittedly more of a psychological deterrent in recent years because of their decreasing numbers as bases closed.

Although 19,000 United Nations troops remain, the American physical presence, with tanks and helicopters and a force as large as 26,000, acted as a psychological deterrent.

Peter G. Grennan, a stock index futures analyst at Shearson Lehman Brothers Inc., said program trading was "a psychological deterrent to the commitment of cash" to stocks.

There does not seem to be much available research to indicate whether longer barbs are actually more effective in resisting penetration, but they provide a stronger psychological deterrent.

These precautions may provide some degree of protection, and can serve as practical and psychological deterrents to would-be terrorists.

There was also a psychological deterrent in the fact that the door was locked.

Hurting Morale, Critics Say Officials say it also serves as a psychological deterrent to wrongdoing because corrupt officers can never be certain if fellow officers will report their actions.

Some say public shelters can be a psychological deterrent.

Otherwise, he added, "we are just adding a small psychological deterrent."

Patrol dogs are trained in building searches, area searches, officer protection, crowd control, trailing, and provide a strong psychological deterrent to certain types of criminal misconduct.