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Perception of simultaneous stroboscopic movements in different directions and the gestalttheory hypothesis of physiological short circuiting
n of several
ha-t-circ~~it’ in order to explain the phe(: describeq the experience he has made simultaneous apparent movements in different s apparent movement in h To explain this phe-
ypothesis of ‘kurz-
zone of visual eld, two clearly wlmse directiom are orthogonal; 0rizontalt line time, they perceive the right to left,
ich together form a-
tents of two distinct figures (circle and quadraqgular eta1 or centrifugal irectbn) are therefore aintains that these resul sis crf ‘short-circuitimg’, advance act9 ‘to accept the t e existence of a s~Qrtacircuit Or 0 of retinal fusio re ldiRerence in , in the case 0f existence of a tw0-w
LI ._
ess :
en&e1obtained the si o&e directions, an and b&‘-b”) f a-b, in centrifugal direct ts &a’ and b’-6’ perform a beta n and the hor tation, give rise to the impression of shrinkage (that is, to EWSSI (1.418),
instead, described of movement and called them ‘combin by using two stroboscopic apparent movements’. is new pheno enon consisted in thl,: de e apparent movements undergoes nce of another apparent
rceptive moveme
articularly suitable to reveal is deflection is the consisting in the simultaneous perception of two ori: ovements, obtained by using two dots place aneous perception of two lines the twSodots are presented al
rtical movement and the two lines c to the first, that is, a ntrary, when thte two
i
rst,case
b
c----
0 ---
3
By using other sti b
lus-situations, a
b
b'
I
II
with optimal times of exposition and pause, we have simultaneous impressions of move
e followin
/
(--_---
Therefore the experiments performed by Neuhaus prove that: (a) in particular stimulus-conditions, it is possible to have visual. apprehension of movement in opposite directions; (b) by using stimulus-systems which allow the perception of different paths of movement, many combinations are prceived which can even dis se themselves so as to shape figures of forms and duration.
ta erent directions can
(1
ssible to receive severa simultaneous impressions of movement in different direc ions (orthogonal, oblique, describing an arc, in the third diAmension); such movements, however, always take place over space areas and the efcre retinal areas which do not coincide or which are placed on different planes. he movements which (2) It is sometimes possible to prove t er, thus causing; the are perceived simultaneously influence one deviation cbfthe path of o e of the apparen ments, swing to b.ha: resence of another movement different1 It appears, therefore, tha much of its importance irn so the investigations carried ou there emerged precise phen perceiving two simultaneou and in opposite directi It is precisely in order to better i ility that I have cinried out som
ve:stigate
the
existence
eriments usin
of
SW
aratus
0a sources of light with an alternative distribut’ ing from 1 to set; (b) an impulse of rectangular shape, adjustble in connection to pause, which makes it possible to pary ad lib. the ratio dark and light w thout altering the fre
196
6. C. ZAPPARQEI
(c) the possibility of adjusting the light withiD a range of one to ten (with maximum i oup of projector3 connected wit the source od the impulses, hich, according to need, special stencils can be applied bearing tide tigurcs chosen for the test. The with carblon incandescent lamps, so as to reduce to a minimu the time lag between light and dark; (e) a ‘screen on which the figures chosen for the experiment where shown. Subjects were placed facing it, at a d stance of oile and a ‘half ~~:tres. Thanks to this equiplment it is possible to obtain condition3 oE stroboscopic stimulation b;y presenting a succession of two different stimuli, a and G: separated or not by a pause (rp y; 0). The subject3 who undertook the tests were 5, all of them already trained to such investigations oi stroboscopic movements.
TEST 1
F’t%sentation a consisted of a disk and a vertical line placed at a &Lance of 5 O. The disk was placed at the left of the field, the line zt the right; the two figure3 being on a horizontal line. In presentation b the positions of the disk and line were identical but rrversed.
n the same exposition time (e’=e”=SOO sigm was used for a and b, causing b to appear as soon as the ex sit ion of 12was terminated, that is, using values p := 0, presentiag a and b in succession, with rhythm a, b, a, b u . . so lth -MISalways = 0, the subjects described the situation a3 follows: ‘ :novement of two figures, a bright straight line and a bright disk, movi!ilg simultaneously in opposite directions along the same path from righq to lef!t and vic,e-versa.’ The: same impression of a dab 7-b simultaneous apparent movement is obt.Cned when groups of two figures other than these are used. For instance, presentation CImay be a square or a triangle or a row of dots laced vertically to the right and a disk to the left; in presentation b, a disk to the right and a square or a triangle or dots in rows vertically
re the existence of particular situadouble simultaneous apparent move-
estion is: would it
‘EST
3
resentatiosl a consists of two disks place at a distance of 5’; e disk of the same shape, co1 resentation I) being a sition between the two disks ity, occl.,pying a mi rt, corresponds to that employed by uhts-situation euhaus and described above. ith exposition time e’=e”=-500 sigma and p ==O, the rhythm of presentation being a-b-a, two movements in opposite dire&ions are perceived. These, however, cover only a pat o:,n the periphery to the centre and vice-versa., elements are transformed in one sing16 centra or the central element becomes two lateral eFnents In fact, this jis how the subjects describe this situation: ‘two bright disks which move towards the c:entre and superimpose in one central image to resume their starting posi,tion’.
198
6.
C. ZAPPAROLI
The only remarkable difference with respect to what served lies in the fact that for Neuhaus the ‘Gegenbewegung’ is obtained only with values of 2’15’; while in my experience ‘Gegen can be realized even with angular values of plus two do urthermore, by vaaying the time of pause between stimuli azd using the technique of serial presentation, we have: ‘on the left, the apparent movement of a bright disk moving from the outside to the centre and vice-versa; on the right, a bright disk where light goes on and off with a gamma movement, that is, with modalities complstely independent of the element which was seen as moving. If the attention position is altered also, the location of the two phenomena is reversed so that w‘hat is perceived is, to the right, the movement of a luminous disk and to the left, the gamma movement of an element wL% remains, located in the same spatial locus’.
If the duration of phase Ib is curtailed, that is, if e” is reduced or if she ratio e’/‘e” is altered, the perceptive situation is radically modified In fact, if .for stimulation Q, a time of 500 sigma is used and fc stimulstian b, a time of 80 sigma, with stimtilation alternation a, b, Q, the subjects see: ‘two disks, one to the left and the other to the right* moving if1 opposite directions, exchanging their position and soon afte I resuming the starting position’. Subjects, even when aware of the stimulus-situation &I net pereeL? at all th.9 presence of the central element as presented irl b. Subjects, furthermore, observed that zhe whole situation appears ta be characterized by a brief superimposition of the disk to the right with the one to the left and vice-versa, which, as they move towards each other, pass through the unseen central disk. If the two disks of situation a present a chromatic difference, i for instance, the right hand disk is red and the left hand one is green, subjects still perceive a double m\ovement, but with an added feeling of somethnng paradoxical. his is how they descri the situatio*n: “two ciiEks, a red one and a green one, moving in o osite directio exchange their respective positions and soon after revert to the starting itiur;. Although the two disks give the impression of movemernt, y a%o, paradoxically, give the impression of not having move#. e inconsistency derives from the fact that the red dot never becomes one with tic: green, while the central disk presented in b position,
B
S
ST
NT
move sim~lta~eo~sl~
of perceiving two e directions of equal between two loci. ent in favour of the (a) on the phenome 1 plane, a new ar equivalence bet a real and an a arent movement; (b) on the theoretical plane, so e considerations about the validity of certain hypotheses advanced by sychologists. _ ask ourselves whether the experi In fact, we our research tests really ntradict the physiological obtained throu ‘erthei:mer, and therefore rt-circuit’, prop hypothesis’ of ‘that to refuse the whether it is correct to state,, as the existence of a ‘short-circuit’ or of processes of retinal assumptio fusion or the existence of a mere difference of potential be stimulated loci, means, in the ca:;e of the phenomena des assume the existence of a two- y process occurring multaneously on one and the same surface, ea par-t of which acts ‘w 1lYindependently’. First of all, we must consider that hypothesis only to supply a psy&ological frame as a basis for apparent movement. Therefore it is not determinant for the principles of
orie: it is only one of it
Saj!S,
OLDSTEIN
WtZ!
is obtained ut there is noth which take place at central level, r ow, in fact, whether there ar occur in the same way as biol erefore, if we take into co which take place under conditions of s tioned research tests, it ses
ena are s
mganic eleven ts’. e Gestalttheorie could be questioned, since biological forms also
arranged on the basis of the pri functionalism: a principle which seems hardly satisfact a to describe the arrangement Gi physical forms. e processes of integration at central eve1 -which, accsrdin oehler and associates, take place throug can be assimilated to the mechanisms r ysical forms, must therefore be recons ct is, by carrying out research tests which may allow: (a) on the pher
nal plane, to lar to those
EFERENCES
1918.
Ueber Scheinbewegungskombination, Arch. d. ges. Psychol. 33-282. 1926. An experimental investigation of the determinants of appaikt visuial movement. Am. J. Psych. , 469-5~~1. 1915. iDe:r Aufbau des Organismus rstnch translation: a structure Ide l’organisme. Paris: allimard.
t
ovimenti
in
oeulari.
eve osservazioni
sulla comhinazione
di movimenti
ha-t-circ~~it’ in order to explain the phe(: describeq the experience he has made simultaneous apparent movements in different s apparent movement in h To explain this phe-
ypothesis of ‘kurz-
zone of visual eld, two clearly wlmse directiom are orthogonal; 0rizontalt line time, they perceive the right to left,
ich together form a-
tents of two distinct figures (circle and quadraqgular eta1 or centrifugal irectbn) are therefore aintains that these resul sis crf ‘short-circuitimg’, advance act9 ‘to accept the t e existence of a s~Qrtacircuit Or 0 of retinal fusio re ldiRerence in , in the case 0f existence of a tw0-w
LI ._
ess :
en&e1obtained the si o&e directions, an and b&‘-b”) f a-b, in centrifugal direct ts &a’ and b’-6’ perform a beta n and the hor tation, give rise to the impression of shrinkage (that is, to EWSSI (1.418),
instead, described of movement and called them ‘combin by using two stroboscopic apparent movements’. is new pheno enon consisted in thl,: de e apparent movements undergoes nce of another apparent
rceptive moveme
articularly suitable to reveal is deflection is the consisting in the simultaneous perception of two ori: ovements, obtained by using two dots place aneous perception of two lines the twSodots are presented al
rtical movement and the two lines c to the first, that is, a ntrary, when thte two
i
rst,case
b
c----
0 ---
3
By using other sti b
lus-situations, a
b
b'
I
II
with optimal times of exposition and pause, we have simultaneous impressions of move
e followin
/
(--_---
Therefore the experiments performed by Neuhaus prove that: (a) in particular stimulus-conditions, it is possible to have visual. apprehension of movement in opposite directions; (b) by using stimulus-systems which allow the perception of different paths of movement, many combinations are prceived which can even dis se themselves so as to shape figures of forms and duration.
ta erent directions can
(1
ssible to receive severa simultaneous impressions of movement in different direc ions (orthogonal, oblique, describing an arc, in the third diAmension); such movements, however, always take place over space areas and the efcre retinal areas which do not coincide or which are placed on different planes. he movements which (2) It is sometimes possible to prove t er, thus causing; the are perceived simultaneously influence one deviation cbfthe path of o e of the apparen ments, swing to b.ha: resence of another movement different1 It appears, therefore, tha much of its importance irn so the investigations carried ou there emerged precise phen perceiving two simultaneou and in opposite directi It is precisely in order to better i ility that I have cinried out som
ve:stigate
the
existence
eriments usin
of
SW
aratus
0a sources of light with an alternative distribut’ ing from 1 to set; (b) an impulse of rectangular shape, adjustble in connection to pause, which makes it possible to pary ad lib. the ratio dark and light w thout altering the fre
196
6. C. ZAPPARQEI
(c) the possibility of adjusting the light withiD a range of one to ten (with maximum i oup of projector3 connected wit the source od the impulses, hich, according to need, special stencils can be applied bearing tide tigurcs chosen for the test. The with carblon incandescent lamps, so as to reduce to a minimu the time lag between light and dark; (e) a ‘screen on which the figures chosen for the experiment where shown. Subjects were placed facing it, at a d stance of oile and a ‘half ~~:tres. Thanks to this equiplment it is possible to obtain condition3 oE stroboscopic stimulation b;y presenting a succession of two different stimuli, a and G: separated or not by a pause (rp y; 0). The subject3 who undertook the tests were 5, all of them already trained to such investigations oi stroboscopic movements.
TEST 1
F’t%sentation a consisted of a disk and a vertical line placed at a &Lance of 5 O. The disk was placed at the left of the field, the line zt the right; the two figure3 being on a horizontal line. In presentation b the positions of the disk and line were identical but rrversed.
n the same exposition time (e’=e”=SOO sigm was used for a and b, causing b to appear as soon as the ex sit ion of 12was terminated, that is, using values p := 0, presentiag a and b in succession, with rhythm a, b, a, b u . . so lth -MISalways = 0, the subjects described the situation a3 follows: ‘ :novement of two figures, a bright straight line and a bright disk, movi!ilg simultaneously in opposite directions along the same path from righq to lef!t and vic,e-versa.’ The: same impression of a dab 7-b simultaneous apparent movement is obt.Cned when groups of two figures other than these are used. For instance, presentation CImay be a square or a triangle or a row of dots laced vertically to the right and a disk to the left; in presentation b, a disk to the right and a square or a triangle or dots in rows vertically
re the existence of particular situadouble simultaneous apparent move-
estion is: would it
‘EST
3
resentatiosl a consists of two disks place at a distance of 5’; e disk of the same shape, co1 resentation I) being a sition between the two disks ity, occl.,pying a mi rt, corresponds to that employed by uhts-situation euhaus and described above. ith exposition time e’=e”=-500 sigma and p ==O, the rhythm of presentation being a-b-a, two movements in opposite dire&ions are perceived. These, however, cover only a pat o:,n the periphery to the centre and vice-versa., elements are transformed in one sing16 centra or the central element becomes two lateral eFnents In fact, this jis how the subjects describe this situation: ‘two bright disks which move towards the c:entre and superimpose in one central image to resume their starting posi,tion’.
198
6.
C. ZAPPAROLI
The only remarkable difference with respect to what served lies in the fact that for Neuhaus the ‘Gegenbewegung’ is obtained only with values of 2’15’; while in my experience ‘Gegen can be realized even with angular values of plus two do urthermore, by vaaying the time of pause between stimuli azd using the technique of serial presentation, we have: ‘on the left, the apparent movement of a bright disk moving from the outside to the centre and vice-versa; on the right, a bright disk where light goes on and off with a gamma movement, that is, with modalities complstely independent of the element which was seen as moving. If the attention position is altered also, the location of the two phenomena is reversed so that w‘hat is perceived is, to the right, the movement of a luminous disk and to the left, the gamma movement of an element wL% remains, located in the same spatial locus’.
If the duration of phase Ib is curtailed, that is, if e” is reduced or if she ratio e’/‘e” is altered, the perceptive situation is radically modified In fact, if .for stimulation Q, a time of 500 sigma is used and fc stimulstian b, a time of 80 sigma, with stimtilation alternation a, b, Q, the subjects see: ‘two disks, one to the left and the other to the right* moving if1 opposite directions, exchanging their position and soon afte I resuming the starting position’. Subjects, even when aware of the stimulus-situation &I net pereeL? at all th.9 presence of the central element as presented irl b. Subjects, furthermore, observed that zhe whole situation appears ta be characterized by a brief superimposition of the disk to the right with the one to the left and vice-versa, which, as they move towards each other, pass through the unseen central disk. If the two disks of situation a present a chromatic difference, i for instance, the right hand disk is red and the left hand one is green, subjects still perceive a double m\ovement, but with an added feeling of somethnng paradoxical. his is how they descri the situatio*n: “two ciiEks, a red one and a green one, moving in o osite directio exchange their respective positions and soon after revert to the starting itiur;. Although the two disks give the impression of movemernt, y a%o, paradoxically, give the impression of not having move#. e inconsistency derives from the fact that the red dot never becomes one with tic: green, while the central disk presented in b position,
B
S
ST
NT
move sim~lta~eo~sl~
of perceiving two e directions of equal between two loci. ent in favour of the (a) on the phenome 1 plane, a new ar equivalence bet a real and an a arent movement; (b) on the theoretical plane, so e considerations about the validity of certain hypotheses advanced by sychologists. _ ask ourselves whether the experi In fact, we our research tests really ntradict the physiological obtained throu ‘erthei:mer, and therefore rt-circuit’, prop hypothesis’ of ‘that to refuse the whether it is correct to state,, as the existence of a ‘short-circuit’ or of processes of retinal assumptio fusion or the existence of a mere difference of potential be stimulated loci, means, in the ca:;e of the phenomena des assume the existence of a two- y process occurring multaneously on one and the same surface, ea par-t of which acts ‘w 1lYindependently’. First of all, we must consider that hypothesis only to supply a psy&ological frame as a basis for apparent movement. Therefore it is not determinant for the principles of
orie: it is only one of it
Saj!S,
OLDSTEIN
WtZ!
is obtained ut there is noth which take place at central level, r ow, in fact, whether there ar occur in the same way as biol erefore, if we take into co which take place under conditions of s tioned research tests, it ses
ena are s
mganic eleven ts’. e Gestalttheorie could be questioned, since biological forms also
arranged on the basis of the pri functionalism: a principle which seems hardly satisfact a to describe the arrangement Gi physical forms. e processes of integration at central eve1 -which, accsrdin oehler and associates, take place throug can be assimilated to the mechanisms r ysical forms, must therefore be recons ct is, by carrying out research tests which may allow: (a) on the pher
nal plane, to lar to those
EFERENCES
1918.
Ueber Scheinbewegungskombination, Arch. d. ges. Psychol. 33-282. 1926. An experimental investigation of the determinants of appaikt visuial movement. Am. J. Psych. , 469-5~~1. 1915. iDe:r Aufbau des Organismus rstnch translation: a structure Ide l’organisme. Paris: allimard.
t
ovimenti
in
oeulari.
eve osservazioni
sulla comhinazione
di movimenti