and B is the stronger. If task-set or intention
enhances the effectiveness of a size cue, Card A
should appear to be more distant in the configura-
tion when the task is to judge its depth position
with respect to Card B rather than with respect
to Card D, Whether or not this result will occur
constitutes a test of the ability of task-set to
modify a perceived depth by means of the inter-
mediary process of cue-enhancement.

Two controls were used. These are illustrated
by the displays of Fig. 1b and 1c. If O used
the size cues to depth appropriately, Card A
should have appeared approximately at the dis-
tance of Card D in the display of Fig. 1b, and
behind Card B in the display of Fig. 1c. It was
required, therefore, that O perceive Card A as
more distant than Card B in the display illus-
trated in Fig. 1c so that the results from that O
could be used in the study. It was also required
that the interposition cue be effective, i.e., that
Card D should appear in front of Card B in
Fig. la. The latter requirement insured that
Card A would appear at different distances
whenever a change occurred in the relative ef-
fectiveness of Cards B and D in determining
the apparent depth position of Card A.

e-— dog —>!— dan
3

Observer o
D |

aa as|
kdb 2T >

Fiaurs 2, A schematic top-view drawing illustrating the
possible enhancement of the effectiveness of size cues
as a function of task-set.

HI. Results.

Expected Results, The results which would
be expected if task-set were to modify perceived
depth are illustrated in Fig. 2. Figure 2 is a
top view schematic drawing indicating the ex-
pected apparent positions of the objects shown

in the display of Fig. 1a. The prime notation
is used to indicate that perceptions are being
represented, with the pair of cards being judged
shown by the subscripts associated with the per-
ceived depth d’. Two apparent depth positions
of Card A are indicated. The position A’, is a
perceived position of Card A which is expected
to occur with the display of Fig. la when the
task is to judge where Card A appears with re-
spect to Card D. The position A’; is a perceived
position of Card A which is expected to occur
with the display of Fig. 1a when the task is to
judge where A appears with respect to B. If
task-set is effective, A’, rather than A’; should
be closer to O with this expected difference
labeled 2T. Half this difference (T) can be at-
tributed to the intention of judging the depth
position of Card A with respect to one of the
other cards. It follows from Fig. 2 that the
average value (T) of the effect of task-set on
perceived depth is
T= dps +d’na—d’pa (1)
2

where d’pp, d’n, and d’p, are the perceived
depths between Cards D and B, Cards B and A
and Cards D and A respectively.

Obtained Results. The average results from
the relative depth judgments are given in Table
1. Each datum entry in Table 1 is an average
of 20 scores, one from each O where each score
is the mean of three kinesthetic adjustments
of the hand apparatus. A positive value in
Table 1 indicates that Card A appeared behind
the card with which it was being judged and a
negative value indicates the converse. Accord-
ing to the scores indicating the perceived depth
between Cards D and B, the interposition cue
resulting from Object C was effective, ie., D was
perceived to be in front of B with an average
value of 18.4 cm. However, the scores from
11 Os indicated that Card A was not perceived
to be more distant than Card B under the con-
trol conditions illustrated in Fig. le, ie. with
Card D absent. Clearly, if A did not appear
behind B with D absent, the effect of task-set
in judging the perceived depth between B and A
under the conditions of Fig. la (D_ present)
would be difficult to evaluate. Therefore, 11
other Os were substituted in the study for the
Os who did not perceive A as more distant than
B in the control situation (Fig. 1c). The value





O (305 em.). As is indicated in Fig. 1, Object
C appeared to overlay Card B and to be over-
layed by Card D. This effect was produced by
cutting away 22.4% of the upper right area of
Card B and 4% of the upper right area of Card
C, and carefully fitting the objects together. The
positions of the cards in each of the displays were
always the same. The position of Card A was
15 cm. to the right of Card B and 15 cm. below
Card D. The luminance of the playing cards
and Object C was 3.0 and 0.5 ft.—L, respectively,
as measured from the position of O’s eye. Only
the objects shown in Fig. 1 were visible with the
remainder of the field of view in darkness. Ob-
jects A, B, and D appeared to O as seven-of-
spades playing cards and Object C appeared to
be a gray square. Only one of the displays in
Fig. 1 was presented at any one time. Two light
boxes were used in producing the displays. One
light box was used to transilluminate the dis-
plays of Fig. 1a and 1b with the latter display
being produced from the former by carefully
covering Card B. <A separate light box was
used for the display of Fig. 1c. A partially-
transmitting, partially-reflecting mirror permit-
ted the display of Fig. 1c to be presented at the
same optical distance and direction as the dis-
plays of Fig. 1a or 1b.

The viewing position of O was enclosed with
black velveteen and contained a head and chin
rest and a viewing aperture. A light-adaptation
surface (3 ft.—L) located to the left of O’s po-
sition could be turned on or off by the experi-
menter (E) for the purpose of light adapting
O. An apparatus for measuring perceived depth
was also located at the position of O. It con-
sisted of two vertical rods positioned at about
the level of O’s waist with the right rod movable
laterally. O grasped the rods, one in each hand
and adjusted the lateral distance between the
rods until this distance seemed to be equal to the
perceived depth between the designated playing
cards. The rods were invisible to O, with the
hand adjustments being made kinesthetically.
An attached centimeter rule permitted E to note
the adjusted separation of the rods. During
the judgments, the interior of the viewing posi-
tion was completely dark, i.e., no objects or sur-
faces were visible to O except the objects of the
display.

Twenty men served as Os. Each O had a
visual acuity in his right eye (corrected if neces-

sary) of at least 20/20. There were five experi-
mental tasks :

Task (1) To indicate the perceived depth be-
tween Cards A and D with Card B present
(Fig. 1a).

Task (2) To indicate the perceived depth be-
tween Cards A and D with Card B absent
(Fig. 1b).

Task (8) To indicate the perceived depth be-
tween Cards A and B with Card D absent
(Fig. 1c).

Task (4) To indicate the perceived depth he-
tween Cards A and B with Card D present
(Fig. 1a).

Task (5) To indicate the perceived depth be-
tween Cards B and D (Fig. 1a).

Each O made three judgments of the depth
between two designated playing cards and, fol-
lowing this, faced the light adaptation surface
which was turned on for approximately 10 sec.
This procedure was repeated for each of the five
tasks. The order in which the five tasks were
completed was systematically varied between Os.
Prior to participating in the experiment, the
Os were carefully instructed to judge only the
depth between the cards. A small pegboard
with two pegs was used to illustrate the differ-
ence between frontoparallel and depth extents.
Following the experiment, the Os were ques-
tioned to be certain that the extent which was
indicated by the hand adjustment reflected the
perceived depth (not the frontoparallel separa-
tion) between the cards.

The basic design of the experiment can be
discussed with the aid of Fig. la. In Fig. 1a,
Card D which was retinally smaller than Card B
would appear to be more distant than Card B
were it not for the conflicting interposition cue
introduced by Object C. The interposition cue
from Object C caused Card D to appear less
distant than Card B in spite of the relative size
cue between these cards. Under these circum-
stances, consider the perceived relative depth posi-
tion of Card A. According to the size cue between
Cards A and D, Card A should appear at the
distance of Card D, ie. in front of Card B.
But, according to the size cue between Cards A
and B, Card A should appear behind Card B,
ie., also behind Card D. Thus, the apparent
depth position of Card A in the configuration
of objects would depend upon whether the size
cue between Cards A and D or between Cards A


The Average Perceived Depth in Centimeters Between Playing Cards as

Measured by the Hand Adjustments.

Taste 1.
Presence or Perceived Depth
Absence of B of A Behind D
B Present
(Task 1) +13.5+*
B Absent
(Task 2) — 45
Diff. 18.0**

*p<.05 (two-tailed t test, df = 19)
**p<.01 (two-tailed t test, df = 19)

of T as computed from the average results ob-
tained from Tasks 1, 4, and 5 using Equation 1
is 84cm. Using the t test (tio=2.74) this value
is significantly different from zero at the .05
level.

IV. Discussion.

As determined by T, the average perceived
position of A in the configuration of objects was
more distant when A was judged with respect
to B rather than D. The evidence is, therefore,
that the set to judge the depth position of one
object with respect to another object can enhance
the effectiveness of the depth cue between these
objects, as determined in the present experiment
by a change in perceived depth.

If the set to use the size cue between Card A
and one of the other cards had made this rela-
tion completely dominant, the perceived depth
between these two cards should have been the
same as though the third (extraneous) card had
not been present. Thus, the total possible effect
of task-set, in this experiment, can be computed
by substituting in Equation 1, the perceived
depth between A and D and between A and B
as determined from the control situation (Task
2, Fig. 1b and Task 3, Fig. 1c) rather than from
the experimental situation (Tasks 1 and 4, Fig.
la). This maximum possible value of T is 24.1
which is 2.9 times as large as the average value
of T (8.4) obtained from the experimental situa-
tion. Therefore, task-set while of importance
in the present study is not equivalent percep-
tually to removing the extraneous card (the card
not involved in the judgment).

In a previous study®, evidence was provided
for the “adjacency principle” as it relates to size
cues to distance. According to the adjacency
principle, the perceived depth position of an ob-
ject in a configuration of objects is mainly de-
termined by whatever cues occur between it and
adjacent (not displaced) objects. In that ex-

Presence or Perceived Depth

Absence of D of A Behind B
D Absent

(Task 3) +25,2**

D Present

(Task 4) +12.0

Diff. 13.2*

periment, Card A was to the left of Card B
such that it was adjacent to Card B and dis-
placed from Card D. It was found that, al-
though the effect of Card B on the apparent
position of Card A was dominant, some small
effect could be attributed both to Card D and
to task-set. In the present experiment, A was
intentionally equally separated from B and from
D. ‘A method? of calculating the effect of Card
B and of Card D upon the apparent position of
Card A can be applied to the present experiment.
This method determines the effect of Card B by
subtracting thé depth perceived between Card A
and Card D obtained when B is present (Task 1)
from that obtained when B is absent (Task 2).
Similarly, the effect of Card D is determined
by subtracting the perceived depth between Card
A and Card B obtained when D is absent (Task
8) from that obtained when D is present (Task
4). The results are that 18.0 cm. and 13.2 cm.
of depth (see Table 1) can be attributed to Cards
B and D, respectively, with the difference be-
tween these values not significant at the .05 level,
(tio=.61). It can be concluded in agreement
with the adjacency principle, that placing Card
A equally far from Cards B and D approxi-
mately equalizes the effect of Card B and Card D
on Card A.

Since the 18.0 and 13.2 cm. values indicate
the effects on Card A of the presence of the card
not involved in the comparison, they represent
the amount by which this extraneous card is
more effective than the task-set in determining
the apparent depth of Card A. The adjacency
principle and task-set are clearly different and
sometimes antagonistic factors. The adjacency
principle indicates the relative strengths of cues
between objects on the basis of their adjacency
while the effect of set is considered without re-
gard to the relative distance between the objects.
Even under the balanced separations of the pres-
ent experiment in which the effect of task-set


AM 67-18

CUE-ENHANCEMENT AS A FUNCTION OF TASK-SET

Walter C. Gogel

Approved by Released by
J. Roserr Drie, M.D. P. V. Srecer, M.D.
Caer, Civ ArRoMEDICAL Feperat Ai Surczon
InsriruTe

August 1967

FEDERAL AVIATION ADMINISTRATION
Office of Aviation Medicine



would be expected to be maximal, it seems that
the effects involved in the adjacency principle
were stronger than those of the task-set.

It remains to be considered why one-third of
the Os tested in the present study failed to meet
the control requirement that Card A be perceived
as more distant than Card B when Card D was
absent (Fig. 1c). This result can be understood
in terms of the equidistance tendency’ between
Objects A and C. The equidistance tendency
states that in the absence of strong distance cues,
there is a tendency for objects to appear equi-
distant with the strength of this tendency being
inversely related to directional separation. It
will be seen in Fig. 1c, that Object C which ap-
pears in front of B is directionally close to A.
Thus, the size cue to distance which would make
A appear behind B is opposed by the equidistance
tendency which would make A appear at the
distance of C, ie., in front of B. It has been
demonstrated under somewhat similar conditions
that the equidistance tendency can modify the
perceived depth from relative size cues.’ There-

fore, it is likely that even those Os who perceived
Card A to be behind Card B in the control con-
dition did not see A as being as far behind B
as would be expected from the relative size cue
in the absence of Object C.

Vv. Summary.

The present experiment demonstrates that un-
der certain conditions the task-set or intention
of the O can modify the perceived depth between
objects resulting from the relative size cue. This
effect is assumed to occur as a consequence of
the cue enhancement resulting from the intention
directly to compare the particular objects. How-
ever, the effect of task-set while significant in
this experiment must be considered as minor
compared with the influence of surrounding ob-
jects not directly involved in the judgment. A
comparison of the results from the present and
@ previous experiment supports the position that
the relative effectiveness of cues depends upon
the relative separation of the objects (the ad-
jacency principle).

REFERENCES

1. Attrort, F.: Theories of Perception and the Con-
cept of Structure. John Wiley & Sons, 1955.

Symbolic Value
J. Soc.

fo

. Bruner, J, S. and Postman, L.:
as an Organizing Factor in Perception.
Psychol., 1948, 27, 203-208.

3. Duxes, W. F. and Bevan, W., JR.: Size Estimation
and Monetary Value: A Correlation. J. Psychol.,
1952, 34, 48-53.

4. Gisson, J. J.: A Critical Review of the Concept of

Set in Contemporary Experimental Psychology.
Psychol. Bull. 1941, 38, No. 9.

5. Gocen, W. C.: Relative Visual Direction as a Factor

in Relative Distance Perceptions. Psychol. Monogr.,
1956, 70, (11, Whole No. 418), 1-19.

6. Gort, W. C.: Size Cues and the Adjacency Prin-
ciple. CARI Report No. 63-28, Oklahoma City, Okla-
homa, 1963.

7. Gocet, W. C.: The Equidistance Tendency and Its
Consequences. Psychol. Rev., 1965, 64, 153-168.

8. Hazer, R. N.: The Nature of the Effect of Set on
Perception. Psychol. Rev., 1966, 73, 335-350.

9. Wirrreicn, W. F.: The Honi Phenomenon: A case
of selective perceptual distortion. In Explorations
in Transactional Psychology, Franklin P. Kilpatrick
(Ed.). New York University Press, 1961.



Qualified requesters may obtain Aviation Medical Reports from Defense Documentation
Center. The general public may purchase from Clearinghouse for Federal Scientific
and Technical Information, U.S. Dept. of Commerce, Springfield, Va. 22151


CUE-ENHANCEMENT AS A FUNCTION OF TASK-SET*

I. The Problem.

Under flight conditions, as well as in other
situations, judgments of the distances between
objects may depend upon a variety of possible
cues. The importance and role of set (the ob-
server’s intention) in the modification of the
perception of distance has not received extensive
investigation. It seems that set can influence
perception by the process of emphasizing or de-
emphasizing certain aspects or parts of the
stimuli. For example, the set to perceive the
number of letters in a tachistoscopic presentation
may prevent the perception of their color, or the
set to perceive a hidden figure may increase the
likelihood that it will be noticed.* Thus, set
probably has a selective role in perception. But,
whether set also can change the perceived char-
acteristics of the objects is more in doubt..* It
is sometimes considered, for example, that set or
attitude can modify perceived extents. In a
number of instances in which it is asserted that
such effects occur it is not obvious why the re-
sulting perceptual modifications should be in one
direction rather than another. It is not obvious,
for example, why an increase in the value of an
object should make it appear larger** or why
in an Ames distorted room a marital partner
should appear more normal in size than a
stranger.? However, a rationale as to the direc-
tion in which set or intention can affect perceived
extent under certain circumstances is available
as a consequence of the selective role of set in
perception. Task-set could result in the enhance-
ment or increased effectiveness of a particular
cue involved, for example, in determining a
perceived depth. If the increased effectiveness
of this cue results in a change in perceived depth,
it follows that the perceptual change could be
attributed to task-set.

The purpose of the present experiment was to
provide a test of the above rationale for expect-

*The assistance of Henry W. Mertens and James C. Hester
in the conduct of this study is gratefully acknowledged. Dr.
Gogel is now at the Department of Psychology, University
of California, Santa Barbara, California.

ing task-set (intention) to modify perceived ex-
tent. A previous experiment’ has suggested that
under appropriate conditions a perceived depth
could be modified somewhat by the intention of
the observer (O). The appropriate conditions
consisted of a visual situation in which a fa-
miliar object would appear at different depth
positions depending upon the relative dominance
of depth cues occurring between it and two other
objects. Similar conditions were used in the
present study except that the stimuli were es-
pecially arranged to provide a more sensitive
test of the perceptual consequences of task-set.

Il. Method.

Front view schematic diagrams of the three
visual displays used in the present experiment
are shown in Fig. 1. Objects A, B, and D were
positive transparencies of seven-of-spades play-
ing cards. Object B was twice the size of a

EI

Figure 1, A schematic front-view drawing illustrating
the positions of the normal-sized cards (A or D),
the double-sized card (B), and the gray square
(C) for the condition in which all three cards
were present (Fig. 1a) or in which one card was
absent (Fig. 1b or Fig. 1c).

normal playing card (11.4 cm. by 17.8 cm.) and
Objects A and D were each the size of a normal
playing card (5.7 cm. by 8.9 em.). Object C
was formed from a square of neutral density
film (17.8 cm. on a side), All four objects were
transilluminated with white light by mounting
them in front of a diffused source (light box).
All were viewed monocularly (with the right
eye only) and all were at the same distance from