Drive reduction theory

In the 1930s, Clark L. Hull and Kenneth W. Spence introduced the drive-reduction theory. Based on the tendency of an organism to maintain balance by adjusting physiological responses, the drive-reduction theory postulated that motivation is an intervening factor in times of imbalance. Imbalances create need, which in turn create drives both encourage action in order to reduce the drive and meet the need. According to drive-reduction theory, the association of stimulus and response in classi-... 

FIG. 11.1. Reductionism, explanatory and heuristic. The left side illustrates the classical view of theory reduction as an explanatory relation, while the right side illustrates the heuristic use of theory reduction in the text. Highlighted items are those whose discovery drives reduction. In explanatory reduction, the reducing and reduced theories (reductans and reductandum) are in hand and the discovery of bridge principles completes the reduction. In heuristic reduction, the reductandum and invariance principles are in hand and the goal is construction of a reducing theory... 

The symmetrical drive=pain/drive reduction=pleasure theory is an intuitively appealing way to imagine how Mother Nature gets work out of her creatures, and it does avoid the question of why people do not usually become absorbed in self-reward. If relief of craving or resolution of emotion is pleasurable, it seems only good balance that the onset should... 

FIG. 21 Plot of log ki2 vs. AEi/2 showing the dependence of ET rate on the driving force for the reaction between ZnPor and four aqueous reductants. The difference between the half-wave potentials for an aqueous redox species and ZnPor, AE-i/2 = AE° + A°0, where AE° is the difference in the formal potentials of the aqueous redox species and ZnPor and A° is the potential drop across the ITIES. The solid line is the expected behavior based on Marcus theory for X = 0.55 eV and a maximum rate constant of 50 cm s M . (Reprinted from Ref. 49. Copyright 1999 American Chemical Society.)... 

The average chemical potential reduction (driving force) per atom for decay of the grooved profile we have considered is the order of Ap=yD/h, where Q is the atomic volume. The decay rate we have calculated is very non-linear in Ap (e.g. it decreases exponentially with h) and contrasts markedly with theories" based on a linear dependence of the decay rate on Ap. 

A simple diagram depicting the differences between these two complementary theories is shown in Fig. 1, which represents reactions at zero driving force. Thus, the activation energy corresponds to the intrinsic barrier. Marcus theory assumes a harmonic potential for reactants and products and, in its simplest form, assumes that the reactant and product surfaces have the same curvature (Fig. la). In his derivation of the dissociative ET theory, Saveant assumed that the reactants should be described by a Morse potential and that the products should simply be the dissociative part of this potential (Fig. Ib). Some concerns about the latter condition have been raised. " On the other hand, comparison of experimental data pertaining to alkyl halides and peroxides (Section 3) with equations (7) and (8) seems to indicate that the simple model proposed by Saveant for the nuclear factor of the ET rate constant expression satisfactorily describes concerted dissociative reductions in the condensed phase. A similar treatment was used by Wentworth and coworkers to describe dissociative electron attachment to aromatic and alkyl halides in the gas phase. ... 

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