PHYSIOLOGISCIIE PSYCttOLOGIE 809

Kessler Passive-Dependency Scale. (4) By using PD Scale or EEG critical points of tendency, diagnostic determination of passive-dependency de- gree is feasible; both techniques increase reliability.

BRAIN D Y N A M I S M AS R E F L E C T E D IN ILLUSIONS'

G. K. YACORZYIqSKI Chicago, 1il. (USA)

In 1945 the writer with Loyal Davis published material showing that patients with unilateral frontal Iobectomies made more errors on visual illusions than the normal individuals. "Hmse findings would make it appear that many of the visual illusions are due to the way that the cortex functions. As a consequence, an attempt was made to rationalize the illusory figures under a system of postulates with the possibility that tl~ese may reflect the dynamics of the cortex.

Eight postulates were advanced. These were as follows: (1) The neural field forces are organized hi vertical and horizontal axes. These are defined as the fundamental axes. (2) A center of forces exists for any .,~ven incoming stimulus pattern. (3) The forces of the fundamental axes will tend to act upon any given incoming neural pattern not in the fundamental axes in the direction of the incoming pattern to bring the pattern into equilibrium around the center of forces. (4) A stimulus pattern which is congruent with one of the fundamental axes will produce forces away from this ,axis, and these forces will become activated when other stimulus patterns out of equilibrium axe present. (5) When a stimulus patterns out of equilibrium is forced into equilibrium the consequent forces so produced will act upon the stimulus patterns within the field which is formed in the direction of these forces. (6) The in- tensity of the effects and interaction on the adjacent stimulus patterns depends upon the degree of disequilibrium which is present. (7) The intensity of the effects and interaction on the forces on the adjacent stimulus patterns depends upon their proximity. This proximity may be physical or temporal. (8) The greater the intensity of the given force the greater will be its interactive effects.

These postulates are used to explain the phenomena observed on various illusions. The illusions may involve lines and angles, lines and circles, or arcs and lines. The vertical-horizontal illusion makes it appear

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as if some of these forces may be rationalized by attributing to them some of the properties present in an ellipse. Methods of determining the intensity of the forces are discussed.

FA CT ORS D E T E R M I N I N G T H E EFFECTS OF BRAIN I N J U R Y

ON P S Y C H O L O G I C A L TEST P E R F O R M A N C E S

A. SMITH Ox]ord (England)

The numerous studies of effects of human brain lesions on mental functions have shown diverse and contradictory findings from the earliest studies to the present. The inconsistent and paradoxical results of investigations employing identical tests nn apparently similar populations suggest the effects of several soumes of ambigarty, some of which were unavoidable.

Over 10 years ago, three related projects marked a major advance in the controlled study of the effects of brain surgery. The Columbia- Greystone I (2), Columbia-Greystone II (3) and New York State Brain Research (1) projects introduced research design, planned sampling, standard measurement, aad refined statistical analysis into an area that had never been investigated with such precision in the past. The conclusions of the three studies were m~animous: surgical destruction of various circumscribed areas in the forebrain did not result in a "permanent" decrement in intellectual function, although a "drop and rise" pattern for operated subjects was noted in all three studies. The "drop and rise" pattern means that scores of operated subjects declined in the immediate postoperative period, but on successive retests the operated patients tended to regain their original capacities. Where post- operative tests were limited to less tha_n a year, and the initial losses were not entirely regained, some further gain might reasonably be anticipated if retests had been continued, since reexaminations in the Columbia Greystone I project had sbown no difference between operated and control patients one year after operation.

Reexamination of operated and control patients of the New York State Brain Research project after an eight year intervM revealed systematic differences between early postoperative effects and those eight years later. In contrast to the original findings, "drop and rise" patterns were shown