Sixteen Experimental Investigations from the Harvard Psychological Laboratory - Hugo Münsterberg (best life changing books txt) 📗
- Author: Hugo Münsterberg
- Performer: -
Book online «Sixteen Experimental Investigations from the Harvard Psychological Laboratory - Hugo Münsterberg (best life changing books txt) 📗». Author Hugo Münsterberg
than the bands x-9, 9-10, etc., because there the recent or weighted
unit-effects are black, while here they are the respective colors.
Also the bands grow dimmer from x-9 to 15-16, that is, as they
become older, for the small increment of one color which would give
band 15-16 is almost wholly overridden by the larger and fresher mass
of stimulation which makes for mere fusion. This last is true of the
bands always, whatever the rate or width of the rod.
10. In general, equal sectors give equal bands, but if one sector is
considerably more intense than the other, the bands of the brighter
color will, for a broad and swiftly-moving rod, be the broader. The
brighter sector, though equal in width to the other, contributes more
toward determining the fusion-color; and this fact is represented by
an intrusion of the stronger color into the transition-bands, at the
expense of the weaker. For in these, even the decreased amount of the
stronger color, on the side next a strong-color band, is yet more
potent than the increased amount of the feebler color. In order to
observe this fact one must have the rod broad, so as to give a broad
transition-band on which the encroachment of the stronger color may be
evident. The process is the same with a narrow rod and narrow
transition-bands, but, being more limited in extent, it is less easily
observed. The rod must also move rapidly, for otherwise the bands
overlap and become obscure, as will be seen in the next paragraph.
11. If the disc consists of a broad and narrow sector, and if the rod
is broad and moves at first rapidly but more slowly with each new
stroke, there are seen at first broad, faint bands of the
minority-color, and narrow bands of the majority-color. The former
grow continuously more intense as the rod moves more slowly, and grow
narrower in width down to zero; whereupon the other bands seem to
overlap, the overlapped part being doubly deep in color, while the
non-overlapped part has come to be more nearly the color of the minor
sector. The overlapped portion grows in width. As the rate of the rod
now further decreases, a confused state ensues which cannot be
described. When, finally, the rod is moving very slowly, the phenomena
described above in paragraph 9 occur.
The successive changes in appearance as the rod moves more and more
slowly, are due to the factors previously mentioned, and to one other
which follows necessarily from the given conditions but has not yet
been considered. This is the last new principle in the illusion which
we shall have to take up. Just as the transition-bands are regions
where two pure-color bands overlap, so, when the rod is broad and
moves slowly, other overlappings occur to produce more complicated
arrangements.
These can be more compactly shown by diagram than by words. Fig. 10,
a, b and c (Plate VI.), show successively slower speeds of the
rod, while all the other factors are the same. In practice the
tendency is to perceive the transition-bands as parts of the broad
faint band of the minor color, which lies between them. It can be
seen, then, how the narrow major-color bands grow only slightly wider
(Fig. 10, a, b) until they overlap (c); how the broad
minor-color bands grow very narrow and more intense in color, there
being always more of the major color deducted (in b they are reduced
exactly to zero, z, z, z). In c the major-color bands overlap
(o, o, o) to give a narrow but doubly intense major-color band
since, although with one major, two minor locus-bands are deducted.
The other bands also overlap to give complicated combinations between
the o-bands. These mixed bands will be, in part at least,
minor-color bands (q, q, q), since, although a minor locus-band
is here deducted, yet nearly two major locus-bands are also taken,
leaving the minor color to predominate. This corresponds with the
observation above, that, ‘… the non-overlapped part has come to be
more nearly the color of the minor sector.’
A slightly slower speed of the rod would give an irreducible confusion
of bands, since the order in which they overlap becomes very
complicated. Finally, when the rod comes to move very slowly, as in
Fig. 9, the appearance suffers no further change, except for a gradual
narrowing of all the bands, up to the moment when the rod comes to
rest.
It is clear that this last principle adduced, of the multiple
overlapping of bands when the rod is broad and moves slowly, can give
for varying speeds of the rod the greatest variety of combinations of
the bands. Among these is to be included that of no bands at all, as
will be understood from Fig. 11 (Plate VII). And in fact, a little
practice will enable the observer so to adjust the rate of the (broad)
rod to that of the disc that no bands are observable. But care must be
taken here that the eye is rigidly fixated and not attracted into
movement by the rod, since of course if the eye moves with the rod, no
bands can be seen, whatever the rate of movement may be.
Thus, all the phenomena of these illusion-bands have been explained as
the result solely of the hiding by the rod of successive sectors of
the disc. The only physiological principles involved are those (1) of
the duration of after-images, and (2) of their summation into a
characteristic effect. It may have seemed to the reader tedious and
unnecessary so minutely to study the bands, especially the details
last mentioned; yet it was necessary to show how all the possible
observable phenomena arise from the purely geometrical fact that
sectors are successively hidden. Otherwise the assertions of previous
students of the illusion, that more intricate physiological processes
are involved, could not have been refuted. The present writer does not
assert that no processes like contrast, induction, etc., come into
play to modify somewhat the saturation, etc., of the colors in the
bands. It must be here as in every other case of vision. But it is now
demonstrated that these remoter physiological processes contribute
nothing essential to the illusion. For these could be dispensed with
and the illusion would still remain.
[Illustration: PSYCHOLOGICAL REVIEW. MONOGRAPH SUPPLEMENT, 17. PLATE VI.
Fig. 10.]
If any reader still suspects that more is involved than the
persistence of after-images, and their summation into a characteristic
effect, he will find it interesting to study the illusion with a
camera. The ‘physiological’ functions referred to belong as well to
the dry-plate as to the retina, while the former exhibits, presumably,
neither contrast nor induction. The illusion-bands can be easily
photographed in a strong light, if white and black sectors are used in
place of colored ones. It is best to arrange the other variable
factors so as to make the transition-bands as narrow as possible (p.
174, No. 4). The writer has two negatives which show the bands very
well, although so delicately that it is not feasible to try to
reproduce them.
VIII. SOME CONVENIENT DEVICES FOR EXHIBITING THE ILLUSION.
The influence of the width of sector is prettily shown by a special
disc like that shown in Fig. 12 (Plate VII.), where the colors are
dark-red and light-green, the shaded being the darker sector. A narrow
rod passed before such a disc by hand at a moderate rate will give
over the outer ring equally wide green and red bands; but on the inner
rings the red bands grow narrower, the green broader.
The fact that the bands are not ‘images of the rod’ can be shown by
another disc (Fig. 13, Plate VII.). In all three rings the lighter
(green) sector is 60° wide, but disposed on the disc as shown. The
bands are broken into zigzags. The parts over the outer ring lag
behind those over the middle, and these behind those over the inner
ring—‘behind,’ that is, farther behind the rod.
Another effective variation is to use rods alike in color with one or
the other of the sectors. Here it is clear that when the rod hides the
oppositely-colored sector, the deduction of that color is replaced
(not by black, as happens if the rod is black) but by the very color
which is already characteristic of that band. But when the rod hides
the sector of its own color, the deduction is replaced by the very
same color. Thus, bands like colored with the rod gain in depth of
tone, while the other pure-color bands present simply the
fusion-color.
IX. A STROBOSCOPE WHICH DEPENDS ON THE SAME PRINCIPLE.
If one produce the illusion by using for rod, not the pendulum of a
metronome, but a black cardboard sector on a second color-mixer placed
in front of the first and rotating concentrically with it, that is,
with the color-disc, one will observe with the higher speeds of the
rod which are now obtainable several further phenomena, all of which
follow simply from the geometrical relations of disc and rod (now a
rotating sector), as discussed above. The color-mixer in front, which
bears the sector (let it still be called a ‘rod’), should rotate by
hand and independently of the disc behind, whose two sectors are to
give the bands. The sectors of the disc should now be equal, and the
rod needs to be broader than before, say 50° or 60°, since it is to
revolve very rapidly.
First, let the rod and disc rotate in the same direction, the disc at
its former rate, while the rod begins slowly and moves faster and
faster. At first there is a confused appearance of vague, radial
shadows shuffling to and fro. This is because the rod is broad and
moves slowly (cf. p. 196, paragraph II).
As the velocity of the rod increases, a moment will come when the
confusing shadows will resolve themselves into four (sometimes five)
radial bands of one color with four of the other color and the
appropriate transition-bands between them. The bands of either color
are symmetrically disposed over the disc, that is, they lie at right
angles to one another (if there are five bands they lie at angles of
72°, etc.). But this entire system of bands, instead of lying
motionless over the disc as did the systems hitherto described, itself
rotates rapidly in the opposite direction from disc to rod. As the rod
rotates forward yet faster, no change is seen except that the system
of bands moves backward more and more slowly. Thus, if one rotate the
rod with one’s own hand, one has the feeling that the backward
movement of the bands is an inverse function of the increase in
velocity of the rod. And, indeed, as this velocity still increases,
the bands gradually come to rest, although both the disc and the rod
are rotating rapidly.
But the system of bands is at rest for only a particular rate of the
rod. As the latter rotates yet faster, the system of bands now
commences to rotate slowly forward (with the disc and rod), then more
and more rapidly (the velocity of the rod still increasing), until it
finally disintegrates and the bands vanish into the confused flicker
of shadows with which the phenomenon commenced.
[Illustration: PSYCHOLOGICAL REVIEW. MONOGRAPH SUPPLEMENT, 17. PLATE VII.
Fig. 11.
Fig. 12. Fig. 13.]
This cycle now plays itself off in the reverse order if the speed of
the rod is allowed gradually to decrease. The bands appear first
moving forward, then more slowly till they come
Comments (0)