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Perception without awareness
Acta PsycJrologi~x 26 C,1967)148-160: 0 North-Holland Publishing Co., Amsterdam Not to be: ~qxoduced by photoprint or microfilm without written permission from the publisher
K. ML I3ANRl?X’I-I?I.JCWS1 Univer&y
of Utrecht, Utrecht,
j
he Net&erlands
ABSTRACT
Two experiments were carried out in order to re-examine the phenomenon of subliminal perception: c.q. jperc?ption withoat awareness. Sublimi tion, c.q. perception witholit awareness, was rrlefined in terms of the subjects ability to n:sposzd differentially to the cc~~teni: ol! stimuli like words or digits, without having consciously identified their meaning. In the fist experiment, subliminal visual perception was examined in terms of the subjjects’ abihty to respond differcntisrily to Dutch stimulus words of positive versus negative emotional connotation, which were presented at such a Bo-wlevel of light intensity that the subjects were unable to perceive even their :;>resence at the conscious level. The critical measures of the ability to respond difIerentially were the associative reaction times. In the second experiment, which was disguised as being related to extrasensory perception, the number ‘5’ served as the visual stimulus and was prey* sented at such a marginal level of intensity that some of the su consciously perceive it, while the others did not. IIowtAver, all the subjects, also those cf the latter category, were abk to perceive and identify his stimulus when their attention was explicitly called to it, The question was, whether those c,:lbjeets who did not perceive this ma,pginal supraliminal stimulus at the cons:ious level, Grould nevertheless be affected by it in the predicted direction, or not.. Perception without awareness could not b{: demonstrated at either of these two intensities of stimulation. An attempt was made to explain the differences til results between these experiments and those which allegedly have demonSriBtd lthe phenomenon of visu;_d percep !ion without aw,3reness.
The objective
of this experimerlt was a re-e*xami p!3eni:-,nnenonof subliminal perception. It was mainly ins1 oE DIXON (li956) and FUHRER and ERIKSEN (1900). question in their experiments was, u hether human subjects aMe tr> req3un.d differentially to visual pr
emotionally positive versus association reaction
Ial level, the association negative stimulus words woul 11ti,mes to tk po!;itive not been tested, however, and annot be meaningfuily is iaeasure of subliminal perception is conce:med. easures of subliminal perception, i.e., atching of stimulus and response words after the subliminal stimulation, the results of the two above-mentioned experiments were contradictory. ications of subliminal pesception, while Fuhrer a on of subliminal percepe present study exami sing differential ass0 as the crucial measure subliminal eff’ect. A pilot study with a group of thirty subjects tablished the fact that, at the supraliminal level, the subjects indeed reacted differentially to the two groups of stimulus wards used in this experiment. A significant n mber of subjects showed. longer associaon reaction times t the group of emotionally positive stim;rlus words. Ian to thl: group emotionaily negative stimulus words (p = 0.04 :r=:0.04 Wilcoxon matched-pairs signed-ranks ign Test, two-tai his result does no: support the frequently xade test,, two-Gled). !3thesis that emotiorally negative stimulus word,; elicit longer assokttion reaction times than emotionally positive stimulus words. This is P It entir:‘y unexpecte:d, however, since ‘r”NUMB and at there is a close relatic frequency of association Also the in the spoken language is probably a freq W’;J~V cf the stimulus wo factr br whit 1 may affect the association reaction times. Tn any Icase,, since there are several uncontrolled variables influenc ng association
s
erception, because
we have
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. .
0
.
.
e
. .
*
.
*
.
.
.
.
.
.
.
.
.
.
“The instruction was: ‘1 a screen, one at a time, but
going to project a num ith such a weak intensity
t.hat there is a word on the scree the xreen, simultaneously also a wo area,,, where you have seen the other en the light spot d
first word that comes ou are, of course, not suppose name these at the crucial moment’. After the subli inal presentation of the stimulus measurements were take for all stimulus kvords use minal presentation, in orI er to find out at which widt e shutter the stimuhts words could be identified correctly. In this case, of course, the method of increasing the light intensity of the stimuli was used. These threshold measurements were needed, since it had to be demonstrahed that the light intensity of the stimulus words during the subliminal presentation lhad been really sub’liminal, in spite of processes during the course of presentation. evaluation of the : item on the .-program was th uality of the stimulus words Ii: factor v&e antic _KMferential(talSle 2). subjecxs one at a time, and the order of presentation w possible position efiFects,
TABLE
ouwr’s
Semantic
2
lfferential a!;sessir.g the factor ‘value’ s1ecn t
(Bad) lijk
(U&) ‘aardeloa:i (Valueless)
conscious level, are ith longer association reack9n
monstrate with
ccts do not respond
ifferentially to those stimuli, of which they, even iin
TABLE 3
oci&ion reaction tjimes
Subject 1 2
3 4 5 6 ‘7 8 9 10 ld 12 13 14 15 16 17 18 19 20
P
3738 (s&C)
83. L7 39’71 39.24 SOeM 68.62 50.21 35.82 21.73 13.90 32*.:ib 8 4OJ% 21AS 33.49 17.25 48.94 13.78 13.29 34.17 27.88
i
33.10 (set) 81.89 36.57 SO.05 72.92 45.90 38. 19.39 33.01 35.11 19.71 29.97 1§,64 51.01 i5.84 12.611 38.22 24.117
1
+ +
it
037
-- 5.57 -+ 3..!i2 + 0.01 - 3.( + 4.4 -- 3.53 +- 5.69 + 3.‘96 - 0.96 + 7.32 + 3.52 $- 5.54 - 2.07 - 7.21 +- 2.63 - 5,59 -+-7.13
5.51)~ 5.50~
4.50 5.25 5.50 (;o.SO 5.25 4.75 4. 4. 4. 4.
Abbreviations total elf the alssociatt: m reaction times to the crucial. positive stimulus words of series 2 :and 3 added. S total of the association reaction tiliiS to the crucial ne words of sc:ri~ 2 and 3 added. didferences between the positive and ne roups expressed in intensity of the stimuli during subliminal presentation, ex ssed in terms of the width of the shutter. Lit = lowest id~~ntificationthreshold, expressed in terms of the width of th E
=
=
=
sum
25
n
”
3.
R
.
?2 .i
8
z
0
.
.
M.
9-c
0
L.
CL
3
(P
PL*
tD
L.
(“F
ip”
w 3
N.
c
E-i CI
..._ CD
List of questims asked during the interview 1.
w=l deze proef? a ow 1d.0 you feel about tech volgens een bepaald syste ps guewed according to some system after
at vend
PI
2. I-kbt u misschien
ci,jfer h&t u bet meest frequent gegokt? ( called most frequcntl y 2) 4. WeEk cijfer hebtt 1.~het rr&jst freqw called least freqruen;tly?) Is .daar misschim een bepaalde reti~z voor? (Is there perhaps so reason for it?) 6‘ at is bet doe1 van deze piroef? (ViJhat is the o jective of this e -r 1. at is de fnnctie van het scherm in deze pro ? (What is the the ser;een in this expe,-imcnt?) II . IVat hebt u eigenlijk op het sAmm precies gczien? (What ex seen on the screen actuail y 7)
4’ _) .
category (a) were classifkd those subjects, whose responses clearly . rry had perceived t C, number ‘5’ in the ex SWi\kXe (b)
ey
came those subjects who though . hati scsmet’imessee] ber on the screen.
clear.ly suggeskii tf,at they the bhck circle. To the questi,3n:
rot_hirag on the ‘
is the objective of this experiy with some t t
5~3~0~~~ iyercepti on. order to make sure that anI subjects met the he stimulrus when their at;iteMion Id IXEaSUirements; were done afte did not meet this criterion, and and nat used for processing the results of the
eat
two
hypot eses wze teste
jects of the aware g re expected to call (‘guess”) the or.s frelquently duri e experimental series 1 series since, due to their conscious awareness of t i;~~~al stimulus, they should respond to its suggestive influence.
SS
7
f the unaware
independent
double-check
is result, of
c9uzx,
on the
casts grave
.
.
TABLE
5
Frequency d
-
1,
t
+a
!i
4
-f-l
IO
3 3
5
-1
5 4
-=--I
0
6 6 12 5 5;
6 4 5 4 3
j-2 -+‘7 +-I j-2
13
4
--I- 9 -t=
1 5 4
0
i5
7
-- 3 -I-
8 5
6
5
4-4
ter
es
According to us, in such a case ect’s awareness of 0 use stimuli whit al %a their purely structural which we cousi er adequate for the p of wfnich they are not consciously aware. EFERENCES
oblemen der subliminale . A. DESLA, 1937.
e ‘tr ,:est voorkomende woorden van een onderz dracht van het Departement van Br,derwijs en DIXON,M. F., 1958. The effect of subliminal stimulation verbal behavior. 3. Abn. Sot. Psychol. 57, 29-36. FUHRER,M. J. and C. WV.ERHKSEN, 1960. The unconscious meaning of verbal stimuli. J. Abn. Sot. Psychol. riteitsprofielenmethode van OUWER, IB.J., 1958. Een bewerking van de 1-14. Osgood. Ned. Tijdschr. v. d. Psycho tric statistics for the behavioral sciencesI. New SIEGEL, S., 1956. York: THUMB, A.. and AWBE,1901. Experimentelle Untersuchungen tiller die Analogiebildung. bsychologischen Grundlagen der sprachlichen Leipzig.
K. ML I3ANRl?X’I-I?I.JCWS1 Univer&y
of Utrecht, Utrecht,
j
he Net&erlands
ABSTRACT
Two experiments were carried out in order to re-examine the phenomenon of subliminal perception: c.q. jperc?ption withoat awareness. Sublimi tion, c.q. perception witholit awareness, was rrlefined in terms of the subjects ability to n:sposzd differentially to the cc~~teni: ol! stimuli like words or digits, without having consciously identified their meaning. In the fist experiment, subliminal visual perception was examined in terms of the subjjects’ abihty to respond differcntisrily to Dutch stimulus words of positive versus negative emotional connotation, which were presented at such a Bo-wlevel of light intensity that the subjects were unable to perceive even their :;>resence at the conscious level. The critical measures of the ability to respond difIerentially were the associative reaction times. In the second experiment, which was disguised as being related to extrasensory perception, the number ‘5’ served as the visual stimulus and was prey* sented at such a marginal level of intensity that some of the su consciously perceive it, while the others did not. IIowtAver, all the subjects, also those cf the latter category, were abk to perceive and identify his stimulus when their attention was explicitly called to it, The question was, whether those c,:lbjeets who did not perceive this ma,pginal supraliminal stimulus at the cons:ious level, Grould nevertheless be affected by it in the predicted direction, or not.. Perception without awareness could not b{: demonstrated at either of these two intensities of stimulation. An attempt was made to explain the differences til results between these experiments and those which allegedly have demonSriBtd lthe phenomenon of visu;_d percep !ion without aw,3reness.
The objective
of this experimerlt was a re-e*xami p!3eni:-,nnenonof subliminal perception. It was mainly ins1 oE DIXON (li956) and FUHRER and ERIKSEN (1900). question in their experiments was, u hether human subjects aMe tr> req3un.d differentially to visual pr
emotionally positive versus association reaction
Ial level, the association negative stimulus words woul 11ti,mes to tk po!;itive not been tested, however, and annot be meaningfuily is iaeasure of subliminal perception is conce:med. easures of subliminal perception, i.e., atching of stimulus and response words after the subliminal stimulation, the results of the two above-mentioned experiments were contradictory. ications of subliminal pesception, while Fuhrer a on of subliminal percepe present study exami sing differential ass0 as the crucial measure subliminal eff’ect. A pilot study with a group of thirty subjects tablished the fact that, at the supraliminal level, the subjects indeed reacted differentially to the two groups of stimulus wards used in this experiment. A significant n mber of subjects showed. longer associaon reaction times t the group of emotionally positive stim;rlus words. Ian to thl: group emotionaily negative stimulus words (p = 0.04 :r=:0.04 Wilcoxon matched-pairs signed-ranks ign Test, two-tai his result does no: support the frequently xade test,, two-Gled). !3thesis that emotiorally negative stimulus word,; elicit longer assokttion reaction times than emotionally positive stimulus words. This is P It entir:‘y unexpecte:d, however, since ‘r”NUMB and at there is a close relatic frequency of association Also the in the spoken language is probably a freq W’;J~V cf the stimulus wo factr br whit 1 may affect the association reaction times. Tn any Icase,, since there are several uncontrolled variables influenc ng association
s
erception, because
we have
L
.
* .
.
* .
. .
.
. .
. s
. .
.
.
e
e
. .
.
.
.
.
* .
.
.
.
.
. .
0
.
.
e
. .
*
.
*
.
.
.
.
.
.
.
.
.
.
“The instruction was: ‘1 a screen, one at a time, but
going to project a num ith such a weak intensity
t.hat there is a word on the scree the xreen, simultaneously also a wo area,,, where you have seen the other en the light spot d
first word that comes ou are, of course, not suppose name these at the crucial moment’. After the subli inal presentation of the stimulus measurements were take for all stimulus kvords use minal presentation, in orI er to find out at which widt e shutter the stimuhts words could be identified correctly. In this case, of course, the method of increasing the light intensity of the stimuli was used. These threshold measurements were needed, since it had to be demonstrahed that the light intensity of the stimulus words during the subliminal presentation lhad been really sub’liminal, in spite of processes during the course of presentation. evaluation of the : item on the .-program was th uality of the stimulus words Ii: factor v&e antic _KMferential(talSle 2). subjecxs one at a time, and the order of presentation w possible position efiFects,
TABLE
ouwr’s
Semantic
2
lfferential a!;sessir.g the factor ‘value’ s1ecn t
(Bad) lijk
(U&) ‘aardeloa:i (Valueless)
conscious level, are ith longer association reack9n
monstrate with
ccts do not respond
ifferentially to those stimuli, of which they, even iin
TABLE 3
oci&ion reaction tjimes
Subject 1 2
3 4 5 6 ‘7 8 9 10 ld 12 13 14 15 16 17 18 19 20
P
3738 (s&C)
83. L7 39’71 39.24 SOeM 68.62 50.21 35.82 21.73 13.90 32*.:ib 8 4OJ% 21AS 33.49 17.25 48.94 13.78 13.29 34.17 27.88
i
33.10 (set) 81.89 36.57 SO.05 72.92 45.90 38. 19.39 33.01 35.11 19.71 29.97 1§,64 51.01 i5.84 12.611 38.22 24.117
1
+ +
it
037
-- 5.57 -+ 3..!i2 + 0.01 - 3.( + 4.4 -- 3.53 +- 5.69 + 3.‘96 - 0.96 + 7.32 + 3.52 $- 5.54 - 2.07 - 7.21 +- 2.63 - 5,59 -+-7.13
5.51)~ 5.50~
4.50 5.25 5.50 (;o.SO 5.25 4.75 4. 4. 4. 4.
Abbreviations total elf the alssociatt: m reaction times to the crucial. positive stimulus words of series 2 :and 3 added. S total of the association reaction tiliiS to the crucial ne words of sc:ri~ 2 and 3 added. didferences between the positive and ne roups expressed in intensity of the stimuli during subliminal presentation, ex ssed in terms of the width of the shutter. Lit = lowest id~~ntificationthreshold, expressed in terms of the width of th E
=
=
=
sum
25
n
”
3.
R
.
?2 .i
8
z
0
.
.
M.
9-c
0
L.
CL
3
(P
PL*
tD
L.
(“F
ip”
w 3
N.
c
E-i CI
..._ CD
List of questims asked during the interview 1.
w=l deze proef? a ow 1d.0 you feel about tech volgens een bepaald syste ps guewed according to some system after
at vend
PI
2. I-kbt u misschien
ci,jfer h&t u bet meest frequent gegokt? ( called most frequcntl y 2) 4. WeEk cijfer hebtt 1.~het rr&jst freqw called least freqruen;tly?) Is .daar misschim een bepaalde reti~z voor? (Is there perhaps so reason for it?) 6‘ at is bet doe1 van deze piroef? (ViJhat is the o jective of this e -r 1. at is de fnnctie van het scherm in deze pro ? (What is the the ser;een in this expe,-imcnt?) II . IVat hebt u eigenlijk op het sAmm precies gczien? (What ex seen on the screen actuail y 7)
4’ _) .
category (a) were classifkd those subjects, whose responses clearly . rry had perceived t C, number ‘5’ in the ex SWi\kXe (b)
ey
came those subjects who though . hati scsmet’imessee] ber on the screen.
clear.ly suggeskii tf,at they the bhck circle. To the questi,3n:
rot_hirag on the ‘
is the objective of this experiy with some t t
5~3~0~~~ iyercepti on. order to make sure that anI subjects met the he stimulrus when their at;iteMion Id IXEaSUirements; were done afte did not meet this criterion, and and nat used for processing the results of the
eat
two
hypot eses wze teste
jects of the aware g re expected to call (‘guess”) the or.s frelquently duri e experimental series 1 series since, due to their conscious awareness of t i;~~~al stimulus, they should respond to its suggestive influence.
SS
7
f the unaware
independent
double-check
is result, of
c9uzx,
on the
casts grave
.
.
TABLE
5
Frequency d
-
1,
t
+a
!i
4
-f-l
IO
3 3
5
-1
5 4
-=--I
0
6 6 12 5 5;
6 4 5 4 3
j-2 -+‘7 +-I j-2
13
4
--I- 9 -t=
1 5 4
0
i5
7
-- 3 -I-
8 5
6
5
4-4
ter
es
According to us, in such a case ect’s awareness of 0 use stimuli whit al %a their purely structural which we cousi er adequate for the p of wfnich they are not consciously aware. EFERENCES
oblemen der subliminale . A. DESLA, 1937.
e ‘tr ,:est voorkomende woorden van een onderz dracht van het Departement van Br,derwijs en DIXON,M. F., 1958. The effect of subliminal stimulation verbal behavior. 3. Abn. Sot. Psychol. 57, 29-36. FUHRER,M. J. and C. WV.ERHKSEN, 1960. The unconscious meaning of verbal stimuli. J. Abn. Sot. Psychol. riteitsprofielenmethode van OUWER, IB.J., 1958. Een bewerking van de 1-14. Osgood. Ned. Tijdschr. v. d. Psycho tric statistics for the behavioral sciencesI. New SIEGEL, S., 1956. York: THUMB, A.. and AWBE,1901. Experimentelle Untersuchungen tiller die Analogiebildung. bsychologischen Grundlagen der sprachlichen Leipzig.