In the first section of this paper, adaptive figural (FAE) and spiral (SAE) after-effect processes, in a sample of university students, are examined from their initial changing stages up to more stable stages. The duration of after- effect is used as a unit in ten/thirty massed trials with inducing periods of equal length. The individual processes mainly differ in degree of linear change (decrease-increase) of performance during ten opening trials, and in (initial, mean, final, stabilized) level of performance. Parameters are found for characterizing these variations and expressing the effects of retest after a two week interval. The retest and parallel test coefficients are all positive; .25 to .62 for the parameter of performance change; .46 to .94 for the parameters of performance level. In the second section, it is proposed that the progressive change of after- effect duration dicloses selective emphasis on either intraceptive (intangible, subjective) or extraceptive (tangible, objective) perception, and a heuristic model of interindividual variations in adaptive regulation of quantity attributes of intraceptive perception is outlined. The initial and stabilized levels of after-effect duration and the linear change of after-effect duration before stabilization are used as reference variables. Five subgroups are identified as having different characteristics in these dimension. The subgroups are compared with respect to their predicted social-emotional adjustment, classified as extraverted, ambiverted, introverted, primitive-hysteric, anxiety-hysteric and dysthymic, and measured by means of profile scores on five self-report dimensions from the Maudsley Personality Inventory and the Marke-Nyman Temperament Scale. The predictions made for the subgroups are on the whole confirmed.