Various - Harvard Psychological Studies, Volume 1

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_S._
B^{1-4}¹ 0 2 0 0 0 1 0 1
B^{5-8} 0 0 0 0
B^{9-12}¹ 0 1 0 0 0 1 0 0
B^{13-16} squared 0(2) 1 0(2) 1 0(2) 1 0 0(1) 0 0(1) 0 0(1)
Total 0(2) 4 0(2) 1 0(2) 1 0 2(1) 0 1(1) 0 0(1)
Per cent. 0 25 0 6 0 6 0 13 0 7 0 0

_Hu._
B^{1-4} 1(1) 4 0(1) 1 0(1) 2 1 3 0 2 0 0
B^{5-8} 0 1(1) 0 0(1) 0 0(1) 0 1 0 1 0 1
B^{9-12} 0 1 0 0 0 1 0 0 0 1 0 0
B^{13-16} 0(1) 0 0(1) 0 0(1) 0 0 4 0 0 0 0
Total 1(2) 6(1) 0(2) 1(1) 0(2) 3(1) 1 8 0 4 0 1
Per cent. 7 40 0 7 0 20 6 50 0 25 0 6

_B._
B^{1-4} 1 1(1) 0 0 0 0(1) 0 0
B^{6-8} 1 2 1 2 1 1 1 0 1 0 1 0
B^{9-12} 0 2(1) 0 0(1) 0 0(1) 0(1) 2 0 2 0 1
B^{13-16} 1 3 1 1 1 1 1 2 0 1 0 1
Total 3 8(2) 2 3(1) 2 2(1) 2(1) 4(1) 1 3 1 2
Per cent. 19 57 13 21 13 13 13 27 7 20 7 13

_Ho._
B^{1-4}¹ 3 2(1) 2 2(1) 1 0(1) 1(2) 1(2) 1(2) 0(2) 0(2) 0(2)
B^{6-8} 1 1(1) 1 0(1) 1 0 0 1(1) 1 1 0 1
B^{9-12} 0(1) 1 0(1) 1 0(1) 0 1 1 1 1 0 0
B^{13-16} cubed 0 0 0 0 0 0 0(1) 4 0(1) 2 0(1) 0
Total 4(1) 4(2) 3(1) 3(2) 2(1) 0(1) 2(3) 7(3) 3(3) 4(2) 0(3) 1(2)
Percent. 33 30 25 23 17 0 17 58 25 33 0 8

_Mo._
B^{1-4} 3 3 3 1 4 1 0 2 0 2 0 2
B^{5-8} 1 4 1 1 1 2 1 2(2) 1 1(2) 1 1(2)
B^{9-12} 2 4 2 4 1 4 0(1) 3(1) 1(1) 3(1) 1(1) 2
B^{13-16} 2(2) 4 2(2) 4 2(2) 2 1 4 1 4 1 4
Total 8(2) 15 8(2) 10 8(2) 9 2(1) 11(3) 3(1) 10(3) 3(1) 9(2)
Percent. 57 94 57 63 57 56 13 85 20 79 20 69

¹Four presentations in learning.
squaredFive presentations in learning.
cubedFive days' interval instead of two.

In the following summary the recall after two days is combined from
Tables I. and II. for the three subjects _M_, _S_ and _Hu_, there
being no important difference in the conditions of experimentation.
For the three other subjects this summary is merely a resume of Table
II. The recall after nine and sixteen days in Table II. is omitted,
and will be taken up later. The figures are in all cases based on the
remainders left after those couplets in which indirect associations
occurred were eliminated both from the total number of couplets
learned and from the total number correctly recalled. _E.g._, in the
case of nouns, _M_ learned, in all, 42 couplets in the _A_ and _B_
sets, but since in 3 of them indirect associations occurred, only 39
couplets are left, of which 21 were correctly recalled. This gives 54
per cent.

SUMMARY OF RECALL AFTER TWO DAYS.--FROM TABLES I. AND II.

N. O. V. M.
M. 54 per cent. 62 per cent. 63 per cent. 61 per cent.
S. 8 " 21 " 7 " 12 "
Hu. 11 " 30 " 5 " 59 "
B. 19 " 57 " 13 " 27 "
Ho. 33 " 30 " 17 " 58 "
Mo. 57 " 94 " 13 " 85 "
Av. 30 per cent. 49 per cent. 20 per cent. 50 per cent.

Av. gain in object couplets, 19 per cent.
" " " movement couplets, 30 per cent.

The first question which occurs in examining the foregoing tables is
concerning the method of treating the indirect associations, _i.e._,
obtaining the per cents. The number of couplets correctly recalled may
be divided into two classes: those in which indirect associations did
not occur, and those in which they did occur. Those in which they did
not occur furnish us exactly what we want, for they are results which
are entirely free from indirect associations. In them, therefore, a
comparison can be made between series using objects and activities and
others using images. On the other hand, those correctly recalled
couplets in which indirect associations _did_ occur are not for our
purposes pure material, for they contain not only the object-image
factor but the indirect association factor also. The solution is to
eliminate these latter couplets, _i.e._, subtract them both from the
number correctly recalled and from the total number of couplets in the
set for a given subject. By so doing and by dividing the first
remainder by the second the per cents, in the tables were obtained.
There is one exception to this treatment. The few couplets in which
indirect associations occurred but which were nevertheless
_incorrectly_ recalled are subtracted only from the total number of
couplets in the set.

The method by which the occurrence of indirect associations was
recorded has been already described. It is considered entirely
trustworthy. There is usually little doubt in the mind of a subject
who comprehends what is meant by an indirect association whether or
not such were present in the particular series which has just been
learned. If none occurred in it the subjects always recorded the fact.
That an indirect association should occasionally be present on one day
and absent on a subsequent one is not strange. That a second term
should effect a union between a first and third and thereafter
disappear from consciousness is not an uncommon phenomenon of
association. There were thirteen such cases out of sixty-eight
indirect associations in the _A_, _B_ and _C_ sets. In the tables they
are given as present because their effects are present. When the
reverse was the case, namely, when an indirect association occurred on
the second, ninth or sixteenth day for the first time, it aided in
later recall and was counted thereafter. There were eight such cases
among the sixty-eight indirect associations.

Is it possible that the occurrence of indirect associations in,
_e.g._, two of the four couplets of a series renders the retention of
the other two easier? This could only be so when the intervals between
two couplets in learning were used for review, but such was never the
case. The subjects were required to fill such intervals with
repetitions of the preceding couplet only.

The elimination of the indirect association couplets and the
acceptance of the remainders as fair portrayals of the influence of
objects and movements on recall is therefore a much nearer approach to
truth than would be the retention of the indirectly associated
couplets.

The following conclusions deal with recall after two days only. The
recall after longer intervals will be discussed after Table III.

The summary from Tables I. and II. shows that when objects and nouns
are coupled each with a foreign symbol, four of the six subjects
recall real objects better than images of objects, while two, _M_ and
_Ho_, show little or no preference. The summary also shows that when
body movements and verbs are coupled each with a foreign symbol, five
of the six subjects recall actual movements better than images of
movements, while one subject, _M_, shows no preference. The same
subject also showed no preference for objects. With the subjects _S_
and _B_ the preference for actual movements is not marked, and has
importance only in the light of later experiments to be reported.

The great difference in the retentive power of different subjects is,
as we should expect, very evident. Roughly, they may be divided into
two groups. _M_ and _Mo_ recall much more than the other four. The
small percentage of recall in the case of these four suggested the
next change in the conditions of experimentation, namely, to shorten
with them the intervals between the tests for permanence. This was
accordingly done in the _C_ set. But before giving an account of the
next set we may supplement these results by results obtained from
other subjects.

It was impossible to repeat this set with the same subjects, and
inconvenient, on account of the scarcity of suitable words, to devise
another set just like it. Accordingly, the _B_ set was repeated with
six new subjects. We may interpolate the results here, and then resume
our experiments with the other subjects. The conditions remained the
same as for the other subjects in all respects except the following.
The tests after nine and sixteen days were omitted, and the remaining
test for deferred recall was given after one day instead of after two.
In learning the series, each series was shown four times instead of
three. The results are summarized in the following table. The figures
in the left half show the number of words out of sixteen which were
correctly recalled. The figures in parentheses separate, as before,
the correctly recalled indirect-association couplets. In the right
half of the table the same results, omitting indirect-association
couplets, are given in per cents, to facilitate comparison with the
summary from Tables I. and II.

TABLE III.

SHOWING RECALL AFTER ONE DAY.

N. O. V. M. N. O. V. M.
Bur. 6 10(1) 7(1) 5(4) 38 67 44 31
W. 5(3) 12(1) 6 9 31 75 38 56
Du. 1 11(1) 8 9 6 69 50 56
H. 9(1) 14 8 12 56 88 50 75
Da. 1(3) 7(4) 3(1) 9(3) 7 44 20 56
R. 7(2) 3(3) 5 5(1) 44 19 31 31
Total, 29(9) 57(10) 37(2) 49(8) Av., 30 60 39 51

Av. gain in object couplets, 30 per cent.
" " " movement couplets, 12 per cent.

The table shows that five subjects recall objects better than images
of objects, while one subject recalls images of objects better.
Similarly, three subjects recall actual movements of the body better
than images of the same, while with three neither type has any
advantage.

THE _C_ SET.

In the _C_ set certain conditions were different from the conditions
of the _A_ and _B_ sets. These changes will be described under three
heads: changes in the material; changes in the time conditions; and
changes in the method of presentation.

For lack of monosyllabic English words the verbs and movements were
dissyllabic words. The nouns and objects were monosyllabic, as before.
All were still concrete, and the movements, whether made or imaged,
were still simple. But the movements employed objects, instead of
being merely movements of the body.

For two of the subjects, _M_ and _Mo_, the time intervals between the
tests remained as in the _A_ and the _B_ sets, namely, two days, nine
days, and sixteen days. With the four other subjects, _S, Hu, B,_ and
_Ho_, the number of tests was reduced to three and the intervals were
as follows:

The I. test, which as before was a part of the learning process, was
not counted. The II. test followed from 41/2 to 61/2 hours, or an average
of 5-3/8 hours, after the I. test. The III. test was approximately 16
hours after the II. test for all four subjects.

The series were learned between 10 a.m. and 1:30 p.m., the II. test
was the same day between 4:30 and 5:10 p.m., and the III. test was the
following morning between 8:30 and 9:10 a.m. Each subject of course
came at the same hour each week.

Each series was shown three times, as in the _B_ set.

A change had to be made in the length of exposure of each couplet in
the movement series. For, as a rule, movements employing objects
required a longer time to execute than mere movements of the body.
Five seconds was found to be a suitable length of exposure. To keep
the three other types of series comparable with the movement series,
if possible, their exposure was also increased from 3 to 5 secs. The
interval of 2 secs, at the end of a presentation was omitted, and the
interval between learning and testing reduced from 4 secs, in the _B_
set to 2 secs.

In the movement series of the _A_ and _B_ sets, movements of parts of
the body were chosen. But the number of such movements which a person
can conveniently make while reading words shown through an aperture is
limited, and as stated above no single word was ever used in two
couplets. These were now exhausted. In the _C_ set, therefore,
movements employing objects were substituted. The objects lay on the
table in a row in front of the subject, occupying a space about 50 cm.
from left to right, and were covered by a black cambric cloth. They
were thus all exposed at the same moment by the subject who, at a
signal, laid back the cloth immediately before the series began, and
in the same manner covered them at the end of the third presentation.
Thus the objects were or might be all in view at once, and as a result
the subject usually formed a single mental image of the four objects.

With this kind of material it was no longer necessary for the operator
to show the subject in advance of the series what the movements were
in order to avoid hesitation and confusion, for the objects were of
such a nature as obviously to suggest in connection with the words the
proper movements.

TABLE IV.

SHOWING RECALL AFTER TWO, NINE AND SIXTEEN DAYS FOR TWO SUBJECTS, AND
AFTER FIVE HOURS AND TWENTY-ONE HOURS FOR FOUR OTHER SUBJECTS.

Days. Two. Nine. Sixteen Two. Nine. Sixteen
N. O. N. O. N. O. V. M. V. M. V. M.
Series _M._
C^{1-4} 4 4 4 4 3 2 3 2 2 2 1 1
C^{5-8} 2 2 2 2 2 1 1 1 1 2 1 0
C^{9-12} 3 2 3 1 3 0 2 4 3 2 2 1
C^{13-16} 4 3(1) 4 2(1) 4 2(1) 3 4 2 3 2 3
Total 13 1(1) 13 9(1) 12 5(1) 9 11 8 9 6 5
Per cent. 81 73 81 60 75 33 56 69 50 56 38 31

_Mo_
C^{1-4} 2 4 1 1 1 1 1 4 1 2 1 2
C^{5-8} 3 2 4 1 3 1 4 3(1) 4 3(1) 2 2(1)
C^{9-12} 0 1 0 1 0 1 0 3 0 1 0 2
C^{13-16} 0 0(1) 0 0(1) 0 0(1) 1(1) 4 1(1) 2 0(1) 0
Total 5 7(1) 5 3(1) 4 3(1) 6(1) 14(1) 6(1) 8(1) 3(1) 6(1)
Per cent. 31 46 31 20 25 20 40 93 40 53 20 40

Hours. Five. Twenty-one. Five. Twenty-one
N. O. N. O. V. M. V. M.
Series _S._
C^{1-4} 1 3 1 1 0 1 0 1
C^{5-8} 0(1) 3 0 2 0 1 0 1
C^{9-12} 0(1) 3 0(1) 4 3 4 3 4
C^{13-16} 1 3 1 3 2 3(1) 3 3(1)
Total 2(2) 12 2(1) 10 5 9(1) 6 9(1)
Per cent. 14 75 14 63 33 60 40 60

_Hn._
C^{1-4} 1 4 1 4 0 4 1 4
C^{5-8} 0(2) 1 0(2) 1 0(1) 2 1(1) 2(2)
C^{9-12} 3 4 3 4 2 4 2 4
C^{13-16} 1 3 3 3 0 3(1) 0 2(1)
Total 5(2) 12 7(2) 12 2(1) 13(3) 4(1) 12(3)
Per cent. 36 75 50 75 14 100 29 92

_B._
C^{1-4} 3 4 3 4 3 4 3 4
C^{5-8} 3 2 3 3 2 2 2 4
C^{9-12} 2 4 2 3 2 1 2 2
C^{13-16} 3 4 3 4 2 4 2 4
Total 11 14 11 14 9 11 9 14
Per cent. 69 88 69 88 56 69 56 88

_Ho._
C^{1-4} 3(1) 2(2) 3(1) 2(2) 0 3(1) 0 1(1)
C^{5-8} 3(1) 4 3(1) 4 3 3(1) 3 3(1)
C^{9-12} 1(2) 4 1(2) 4 2(1) 3(1) 2(1) 3(1)
C^{13-16} 0 2 0 2 2 4 2 4
Total 7(4) 12(2) 7(4) 12(2) 7(1) 13(3) 7(1) 11(3)
Per cent. 58 92 58 92 50 100 50 85

The object series were also changed to conform to the movement series.
Formerly the objects had been shown successively through the aperture
and synchronously with their corresponding words; now they were on the
table in front of the subject and all uncovered and covered at once as
in the movement series. The subjects therefore had a single mental
image of these four objects also.

In both the object and the movement series the objects as before were
small and fairly uniform in size and so selected as not to betray to
the subject their presence beneath the cloth in the I. test. In the
II., III. and IV. tests there were no objects on the table.

The previous table shows the results of the _C_ set. The figures give
the number of couplets correct out of four; the figures in brackets
give the number of indirect associations; the total number recalled in
any series is their sum.

In the following summary the recall of _M_ and _Mo_ after two days and
of _S, Hu, B_ and _Ho_ after twenty-one hours are combined.

SUMMARY FROM TABLE IV.

N. O. V. M.
_M._ 81 per cent. 73 per cent. 56 per cent. 69 per cent.
_Mo._ 31 " 46 " 40 " 93 "
_S._ 14 " 63 " 40 " 60 "
_Hu._ 50 " 75 " 29 " 92 "
_B._ 69 " 88 " 56 " 88 "
_Ho._ 58 " 92 " 50 " 85 "
----------- ----------- ----------- -----------
Av. 51 per cent. 73 per cent. 45 per cent. 81 per cent.

Av. gain in object couplets, 22 per cent.
" " " movement couplets, 36 per cent.

Before asking whether the results of the _C_ set confirm the
conclusions already reached, we must compare the conditions of the
three sets to see whether the changes in the conditions in the _C_ set
have rendered it incomparable with the other two. The first change was
the substitution of dissyllabic words in the verb and the movement
series in the place of monosyllabic words. Since the change was made
in both the verb and the movement series their comparability with each
other is not interfered with, and this is the point at issue.
Preliminary tests, however, made it highly probable that simple
concrete dissyllabic words are not more difficult than monosyllabic in
5 secs. exposure. This change is therefore disregarded.

The first important change introduced in the _C_ set was the reduction
of the intervals between the tests for four subjects. The second was
the lengthening of the exposure from 3 to 5 secs. These changes also
do not lessen the comparability of the noun, object, verb and movement
series with one another, since they affected all series of the _C_
set.

The third change in the conditions was the substitution in the
movement series of movements employing objects for movements of the
body alone, and the consequent placing of objects on the table in the
movement and in the object series of which the subject obtained a
single mental image. All of the subjects were of the opinion that this
single mental image was an aid in recall. Each of the objects
contributing to form it was individualized by its spatial order among
the objects on the table. The objects shown through the aperture were
connected merely by temporal contiguity. On this account the object
and the movement series of the _C_ set are not altogether comparable
with those of the _A_ and the _B_ sets. We should expect _a priori_
that the object and the movement series in the _C_ set would be much
better recalled than those of the _A_ and the _B_ sets.

The fourth change was from imaged or made movements of the body alone
to imaged or made movements employing objects. If, as the _A_ and the
_B_ sets have already demonstrated, the presence of objects at all is
an aid to recall, the movement series of the _C_ set should show a
greater gain over their corresponding verb series than the simple
movements of the body in the _A_ and the _B_ sets showed over their
corresponding verb series. For, employing objects in movements is
adding the aid of objects to whatever aid there is in making the
movements.

Turning to the results, we consider the _C_ set by itself with
reference to the effect of the use of objects vs. images in general.
The summary from Table IV. shows that under the conditions given,
after intervals of from slightly less than one day to two days, five
of the six subjects recall object couplets better than noun couplets.
One subject, _M_ recalls noun couplets better. It also shows that
under the conditions and after the intervals mentioned all six
subjects recall movement couplets better than verb couplets. In view
of the small difference here and of his whole record, however, _M_ is
probably to be classed as indifferent in both substantive and action
series.

RECALL AFTER NINE AND SIXTEEN DAYS.

Thus far recall after these longer intervals has not been discussed.
The experiment was originally devised to test recall after two days
only, but it was found that with two of the subjects, _M_ and _Mo_,
recall for greater intervals could be obtained with slight additional
trouble. This was accordingly done in the _B_ and _C_ sets. The
results of the four other subjects in the _B_ set are not so
satisfactory on this point, because not enough was recalled.

The most interesting fact which developed was an apparently slower
rate of forgetting, in many cases, of the nouns and verbs than of the
objects and movements. In the noun-object group of the _B_ set it is
noticeable in three out of the four possible subjects, viz., _B, Ho_,
and _Mo_. _M_ alone does not show it. The two other subjects, _S_ and
_B_, did not recall enough for a comparison. In the verb-movement
group of the _B_ set it is also marked in three out of the four
possible subjects, viz., _M_, _Ho_, and _Mo. B_ alone does not show
it. It is also seen in the _C_ set in the results of _M_ and _Mo_, in
both the noun-object and the verb-movement groups. With the four other
subjects in the _C_ set it could not be noticed, since the series ran
their course in a day. In _M_ (verb-movement group, _C_ set) and _Mo_
(noun-object group, _C_ set) the originally higher object or movement
curves actually fall below their corresponding noun or verb curves.

The results of the tests for recall after nine and sixteen days are
summarized in the following tables. They should be compared with the
recall of these same series after two days given in Tables II. and
IV., nor should it be forgotten that all four types started with
perfect immediate recall. The figures give per cents, correct after
eliminating indirect-association couplets.

TABLE V.

SHOWING RECALL AFTER NINE AND SIXTEEN DAYS.--SUMMARY FROM _B_ SET.

Days. Nine. Sixteen Nine. Sixteen.
N. O. N. O. V. M. V. M.
_M._ 36 38 29 31 56 19 50 31
_S._ 0 6 0 6 0 7 0 0
_Hu._ 0 7 0 20 0 25 0 6
_B._ 13 21 13 13 7 20 7 13
_Ho._ 25 23 17 0 25 33 0 8
_Mo._ 57 63 57 56 20 79 20 69
Av. 22 26 19 21 18 31 13 21

TABLE VI.

SAME FOR _M_ AND _Mo_.--SUMMARY FROM _C_ SET.

Days. Nine. Sixteen. Nine. Sixteen.
N. O. N. O. V. M. V. M.
_M_. 81 60 75 33 50 56 38 31
_Mo_. 31 20 25 20 40 53 20 40

THE _D_ SET.

A few series of nouns, objects, verbs, and movements dissociated from
foreign symbols were obtained. The material was of the same kind as
the words used in the couplet series, being mostly monosyllabic and
seldom dissyllabic words. They had not been previously used with these
subjects. Each series contained ten words or ten objects. The same
kind of precautions were taken as in the couplet sets to avoid
phonetic aids and the juxtaposition of words which suggest each other.
The apparatus employed in the couplet sets was used. The objects in
the object series were shown through the aperture. Visual images were
required in the noun and in the verb series. The noun and the object
series were exposed at the rate of one word every 2 secs. (or 20 secs.
for the series) for _M_, _S_, and _Hu_, and one every 3 secs. (or 30
secs. for the series) for _B_, _Ho_, and _Mo_. Only one exposure of
the series was given. At its completion the subject at once wrote as
many of the words or objects as he could recall. Two days later at the
same hour he was asked to write without further stimulus as many words
of each series as he could recall, classifying them according to their
type of series.