Harvard Psychological Studies, Volume 1 | Page 6

the
phenomenon.
[8] Mach, Ernst, 'Beiträge zur Analyze der Empfindungen,' Jena, 1886.
[9] Mach, op. citat., 2te Aufl., Jena, 1900, S. 96.
It is brought up again by Lipps,[10] who assumes that the streak ought
to dart with the eyes and calls therefore the oppositely moving streak
the 'falsely localized image.' For sake of brevity we may call this the
'false image.' The explanation of Lipps can be pieced together as
follows (ibid., S. 64): "The explanation presupposes that sensations of
eye-movements have nothing to do with the projection of retinal
impressions into the visual field, that is, with the perception of the
mutual relations as to direction and distance, of objects which are
viewed simultaneously.... Undoubtedly, however, sensations of
eye-movements, and of head-and body-movements as well, afford us a
scale for measuring the displacements which our entire visual field and
every point in it undergo within the surrounding totality of space,
which we conceive of as fixed. We estimate according to the length of

such movements, or at least we deduce therefrom, the distance through
fixed space which our view by virtue of these movements has
traversed.... They themselves are nothing for our consciousness but a
series of purely intensive states. But in experience they can come to
indicate distance traversed." Now in turning the eye from a luminous
object, O, to some other fixation-point, P, the distance as simply
contemplated is more or less subdivided or filled in by the objects
which are seen to lie between O and P, or if no such objects are visible
the distance is still felt to consist of an infinity of points; whereas the
muscular innervation which is to carry the eye over this very distance is
an undivided unit. But it is this which gives us our estimate of the arc
we move through, and being thus uninterrupted it will appear shorter
than the contemplated, much subdivided distance OP, just as a
continuous line appears shorter than a broken line. "After such
analogies, now, the movement of the eye from O to P, that is, the arc
which I traverse, must be underestimated" (ibid., S. 67). There is thus a
discrepancy between our two estimates of the distance OP. This
discrepancy is felt during the movement, and can be harmonized only if
we seem to see the two fixation-points move apart, until the arc
between them, in terms of innervation-feeling, feels equal to the
distance OP in terms of its visual subdivisions. Now either O and P can
both seem to move apart from each other, or else one can seem fixed
while the other moves. But the eye has for its goal P, which ought
therefore to have a definite position. "P appears fixed because, as goal,
I hold it fast in my thought" (loc. citat.). It must be O, therefore, which
appears to move; that is, O must dart backward as the eye moves
forward toward P. Thus Lipps explains the illusion.
[10] Lipps, Th., Zeitschrift f. Psychologie u. Physiologie der
Sinnesorgane, 1890, I., S. 60-74.
Such an explanation involves many doubtful presuppositions, but if we
were to grant to Lipps those, the following consideration would
invalidate his account. Whether the feeling of innervation which he
speaks of as being the underestimated factor is supposed to be a true
innervation-feeling in the narrower sense, or a muscular sensation
remembered from past movements, it would in the course of experience

certainly come to be so closely associated with the corresponding
objective distance as not to feel less than this. So far as an
innervation-feeling might allow us to estimate distance, it could have
no other meaning than to represent just that distance through which the
innervation will move the organ in question. If OP is a distance and i is
the feeling of such an innervation as will move the eye through that
distance, it is inconceivable that i, if it represent any distance at all,
should represent any other distance than just OP.
Cornelius[11] brought up the matter a year later than Lipps. Cornelius
criticises the unwarranted presuppositions of Lipps, and himself
suggests that the falsely localized streak is due to a slight rebound
which the eye, having overshot its intended goal, may make in the
opposite direction to regain the mark. This would undoubtedly explain
the phenomenon if such movements of rebound actually took place.
Cornelius himself does not adduce any experiments to corroborate this
account.
[11] Cornelius, C.S., Zeitschrift f. Psychologie u. Physiologie der
Sinnesorgane, 1891, II., S. 164-179.
The writer, therefore, undertook to find out if such movements actually
are made. The observations were made by watching the eyes of several
subjects, who looked repeatedly from one fixation-point to another.
Although sometimes such backward movements seemed indeed to be
made, they were very rare and always very