A New Interpretation of the Substantial Individual Differences in Behavioral Performances

A New Interpretation of the Substantial Individual Differences in Behavioral Performances 

It is a common experience that - independent of method and species used for studying learning-based behavioral modification - the observer rims into substantial individual differences in performance, for reasons unknown. Conceiving learning as a cortical enhancer regulation dependent function, as discussed in Sect. 3.4.2, and recognizing that the enhancer substance exerts its effect in terms of a peculiar bell-shaped dose/response curve (see Fig. 3.11) offers a reasonable interpretation for this remarkable phenomenon. 

As shown in Fig. 3.11, the most effective dose of (-)-BPAP, 0.0005 mg/kg, increased the release of norepinephrine from 4.7 0.10 nM/g (control) to 15.4 0.55 nM/g (P 0.001), but a 100-times higher dose of (-)-BPAP (0.05 mg/kg) did not change it (4.3 0.25 nM/g) (Knoll et al., 2002b). Since an optimum concentration of the enhancer substance was needed for the optimum performance, I postulate that the substantial individual differences found in behavioral performances are due to the peculiar dose-dependency of the endogenous mesencephalic and cortical enhancer substances. 

This approach grants us a new perspective on the results of our two longitudinal studies on rats (Knoll 1988 Knoll et al. 1989, 1994). As an example, let us analyze our second longitudinal study (Knoll et al. 1994) from this perspective. We selected the sexually highest- and lowest-performing individuals from a population of 1,600 rats. 

Considering the unique dose-related effect of an enhancer substance, as shown in Fig. 3.11, we assume that out of the 1,600 rats the 99 HP rats produced their endogenous enhancer substances at the peak of the bell-shaped concentration/effect curve, while the 94 LP rats produced them at the least active part of the curve and the production of the overwhelming majority of the population (1,407 rats) falls between the two extremes. 

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