A also takes the mechanical choice as the small fixed line goes farther from the center; but when the fixed line is large and leaves the center, he reverses the mechanical choice—­evidently because it would take the small line too far out.  As he says, ’he is always disturbed by too large a black space in the center.’

G almost always takes the mechanical choice;—­in one whole set of experiments, in which the fixed line is the large line, he reverses regularly.

H takes for F. (80x10) the mechanical choice only for the positions F. 160 and F. 200—­i.e., only when F. is very far from the center and he wishes V. (160x10) nearer.  For F. (160x10) he makes six such choices out of ten, but for positions F. 160 and F. 200 he has V. 44, 65 and 20.

S takes for F. (160x10) at F. 120, V. 185 and-70; says of V. 185, which is also his choice for F. (160x10) at F. 80, ’I cannot go out further, because it is so hard to take in the whole field.’  For F. (160x10) at F. 200, he has V. 130 and 60; says of V. 60, ’Very agreeable elements in connection with the relation of the two lines.’

C takes for F. (80x10) only one mechanical choice until it is at F. 120.  Then always mechanical, i.e., nearer center; for F. (160x10) makes after the position F. 40 no mechanical choice, i.e., V. is nearer center.

It is evident from the above tables and individual cases that the reversals from the mechanical choice occur only when the mechanical choice would bring both lines in the center, or both near the edges, and the subjective testimony shows from what point of view this appears desirable.  The subjects wish ‘to take in the whole field,’ they wish ’not to be disturbed by too large a black space in the center’; and when, in order to cover in some way the whole space, the small line is drawn in or the large one pushed out, they have, nevertheless, a feeling of equilibrium in spite of the reversal of mechanical balance.

Accepting for the present, without seeking a further psychological explanation, the type of ‘mechanical balance,’ in which amount of space is a substitute for weight, as the one most often observed, we have to seek some point of view from which this entire reversal is intelligible.  For even the feeling that ’the whole field must be covered’ would hardly account for an exact interchanging of positions.  If size gives ‘weight,’ why does it not always do so?  A simple answer would seem to be given by the consideration that we tend to give most attention to the center of a circumscribed space, and that any object in that center will get proportionately more attention than on the outskirts.  The small line near the center, therefore, would attract attention by virtue of its centrality, and thus balance the large line, intrinsically more noticeable but farther away.  Moreover, all the other moments of aesthetic pleasure, derived from the even filling of the space, would work in favor of this arrangement and against the mechanical arrangement, which would leave a large black space in the middle.