Relative Strength of Motivational Excitants

Of the various proposals which have been made for measuring the relative strength of different motivational excitants, that which utilizes the obstruction method seems to be most promising. An animal supposedly motivated by a definite tissue condition is separated by a barrier from an object which will provide the means for restoring organic equilibrium. The usual type of obstruction chamber carries a floor plate or grid charged with electricity. This delivers a series of induction shocks to the animal as it crosses from the starting compartment to that which contains the available equilibrator. By keeping the obstruction constant and varying the type of goal object (food, mate, nest, etc.), the strength of different internal excitants can be measured in terms of the number of times the animal will recross the grid after being returned to the starting compartment before his need is gratified. Measurement can also be made of the amount of voltage necessary to inhibit the animal's approach to the different goals.

It is manifestly impossible to isolate, in any absolute sense, a single drive (excitant) in a complex organism like the white rat. Obviously, the different physiological systems upon which drives are based are more or less interdependent and operate simultaneously when the organism is maintained in a normal or natural state. The best that could be done was to keep drives, other than the one being tested, in a minimum status of quiescence, and such a status had to be empirically determined for each drive and with reference to the general living conditions which prevailed during the investigation. . . . Quiescence of a given drive . . . was accomplished in the following manner: (1) Except when the hunger drive was itself being tested, the animal was taken from a cage which had been continuously supplied with the usual diet of the laboratory. (2) Except when the thirst drive was itself being tested, the animal was taken from a cage which had been continuously supplied with water. (3) Except when the male sex drive was itself being tested, the male had been segregated from females for 35 days; and at approximately this time the male sex drive is at a minimum within the limits of our tests on male sex deprivation. (4) Except when the female sex drive was itself being tested, only females in dioestrum, at which stage the female sex drive is at a minimum, were used.

While it is difficult to estimate the degree to which these studies apply to human conduct, if at all, it seems that some adaptation of the method itself is feasible. "How much is he willing to pay for it?" is the obstruction yardstick which we so frequently use to measure the strength of specific motivations in man. Instead of using money as an obstruction, it could be made a goal, the problem then becoming, "How long will a man endure a condition of hunger or thirst for a fixed sum?" By varying the stipulated time of abstinence systematically and offering the same sum for compliance in each case, a mean time value could be found at which the majority of individuals will endure the several kinds of internal excitants. The difficulties of standardization which would be involved in this procedure are tremendous; and unless we could be reasonably sure that an individual entered successive tests in similar condition, the experiment would lack point.