d harder to

condition was difficult and ci
The Rehearsal-only subjects, on the other
ht have become increasingly frustrated at
to perform better at

excluded th
layed-change, aad
RS because th, were

R the highlighted scrip
1.52). Father

mean time to clk was ner

ume tu dics the

aS NOT a Sis = Measuic ws WOIK-

load, of subjecis had ae move rouble with the di:

i

fh the easier

+ Exper
3 the externa)
retrieval function. Apparen

wing rhe

nity to tailor rehearsal and retrieval ssategies to the

s presented made little diff

way the catcrnai cue

eval function of the cateraal cus was
Feered by vential rehearsal

ence. The rev

v dike

Rar

primer y end w

and retrieval steaicg

GENERAL DISCUSSION

SUPPOrt 2 reirieve:

control task. :t is import

provides conter pro-

spective command can be execared. Having the exter-

the retent
more effective than not ha

nal cue visible dur

pang che cue

cro the Horhand Rer fevel-on

the latency of

Cuing Prospective Memory

ng 2 potential benefiz of beth ree

n thar condition. However, the
-only

hearsal anc
fact that the Rehearsal,
the Neither condition {and getting worse wi

condition was worse than

ing} suggests that zchearsal was of little help:

vai-only conditions may have con ncinued to

and Ret:
perform
effect was

equivalen

‘The external cue presensed in nthe current experi-

ments was very explici In fa
ive co:

ae excernal cue was not sirictly speaking a

suniing that 7 the informa-

ton uncss: ould

have presente tally, end then

ulated the y 2 a less explicic

Subjects as not pe fe
modifi

as accurately in this

ed experimenz. Howevez, we would expec: the

same pattern of results “Boch <
fy = Neither}

i plane ass

velonly > Re-

hearsal- we scored the data us fol-

tows: Corree dlock

ent ic irs origina; dara
destination. Wrong if plene sent to origina! date block

destinat.on. That is. Correer means t

az subjects knew

he dais

destination

sa change (
Having no idea whaz

the correct dest:

e)
hy

was, however, they could only guess among the five

ng destinatiens.
How general is che conclusion
support primarily a retriev

stances s might produce adi

non vould Q alt in ef
The relationship bi
only condvsions may dey



Cuing Prospective Memory

performance is duc to the subject rehearsing the
content during the retention intesval, versus seeing
the cue and retrieving the content when they can
execute it.

The primary goa! of the present research is to
€

ine haw external cues support memory for the
conzent of ¢ to-be-performed action. We disentangled
the rehearsal from rhe retrieval function of a
bined cue by manipulating its temporal availability.
However, ed cue
snotan egue

com-

1¢ to this manipulation, the<o:

ffective trigger in all conditions.

Therefore, we had ro add ¢ second trigger cue that
indicated nothing abour content. One cue supported
con:ent only. the other supported the trigger only.
Before describing in decail the external cues that
were used, we describe the setting for the eaperiment.

Qn

We felt ir was importan
valid approach characteristic of much of prospective
memory research {e.g., Meacham & Leiman, 198
Meacham & Singer, 1977; West, 1988; Wilkins &
Baddeley, 1978), although we required a degree of

aintain the eculogically-

cortrol characteristic of a laboratory-based task (e.
Einstein & McDaniel, 1990; McDaniel & Einstein.
1993). ‘I

The Federal Aviation Administration's Air Traffic
Scenario Test (Avrospace Sciences Inc., 1991} isa PC-
based simulation that provides a fairly complea and
realistic human factors setting, which we modified as
needed, With one exception (Drew, 1940). work on
prospective memory has not been conducted in a
human factors setting. Itisa timely period to examine
prospective memory in air traffic control. Impending

*he following task was chosen.

automation will soon change the way in which con-
trolfers interact with their external memory cues.
Over the next few years, the human-computer inter-
face in the en route’ air traffic control environment

will undergo substantial modifi

ations.

creaung an

in which

oppertu
prospective ¢

tc determine the optimal way

ng should be accomplished.

Air traffic contral
Air traffic control ss avery rich damai
Control

which to

te prospective memory.

memory: they frequenthy

e. use of prospe:

asible fur aitcraft tr

te

have to put something off temporatily, either because
the situation does nor allow it or their workload is too
great. When a controller cannot execute a control
action immediately and has to remember to take that
action in the near future, he or she will often make use
of an external memory aid. This might happen if a
pilot has requested the use of a higher alticude that

cannot be granted until the aircraft is clear of crossing
traffic.

The major rami

ication of he impending automa-
tion on the conzroller’s work environment concerns
the display of flight data not presented on the radar
displey. Presently, controllers receive these flight data
on rectangular paper strips, called flight progress
strips. Vhese are the controllers’ external memory
cues. There is one strip for cack controlled aircraft on
the radar display, each with 3! fields of information,
including the call sign, planned altitude. and destina-
tion. The controller has various lega! responsibilities

that require extensive interaction with and marking of
the strips. Hopkin (1988} and Jackson (1 989), among
others, have speculated that, although this marking of
the strips is at least partially done for legal reasons, it
likely serves to sepporc many cognitive functions that
aid controllers in maintaining their “picture” ef the
airspace (for a review see Cox, 1992; Vortac & Gettys,
1990}.

Prospective memory is one of these cognitive func-
tions. In the current system, controllers mark directly
on the paper flight progress strips, and will often offset
one strip from the others 2s a prospective cue. The
offset strip serves as the triggers the information on the
strip contains the required content regarding what
action should be taken. For example. a pilot may
request a lower altitude, but the contraller cannot do
so until the plane clears crossing traffic. The control-
jer may offset tha: plane's strip as a future reminder to
take this action, and wrize the requested altitude on
the strip to help remember the content of the future

action.

Under the planned automation, these Paper strips
be replaced by e!
sercen. In the new

tronic strips on a computer

system, controllers will inceract
ps indirectly via 2 keyboard and

with Cleon

sans the narian


then disappeared, never to return. In the Both condi-
tion, the command semained visible until the aircraft
left the airspace. In the Rehearsal-only condition, the
command diseppeared 10s before the O appeared. In
the Retrieval-only condition, the command reap-
peared 10 s before the O appeared. The content
component of prospective memory was measured by
the accuracy of sending these aircraft to their correct
changed destination.

As is evident from Figure 2, the subject’s retention
interval could be longer or shorter than 150s depend-
ing on when che subject responded to: 1} the high-
lighted strip, and 2) the appearanc: of the O. For
example, if the subject was slow to respond to the
highlighted strip (¢.g., it took 30 s} and quick to
respond to the OQ (e.g., 9s), the retention interval (the
‘time from the initial encoding of the prospective
command to the t:me that the aircraft was moving and
the prospective command could be executed) was 125 s.
On the other hand, ifthe subject was quick to respond
to the highlighted strip (5 s) and slow to respond to
the © (30 s), the retention interval was 175 s. The
retention interval was under subject control and was
a function of a variety of factors, most notably work-
load.

The trigger component of prospective memory was
measured by the latency to click the O. Air traffic
control is an event-based task {see Einstein &
MeDaniel, 1990). A trigger signals that an action can
be taken, bur does nor require that the action be taken
right now. There was no specific time at which the
prospective command was to be executed (as long es
O was present on the relevant aircraft). Subjects were
simply instructed to be as efficient as possible, which
meant that they should try to get to it as scon as
possible. {n contrast, a time-based prospeczive task
requires O thar an accion must be performed at a
specific time {e.g., taking cupcakes our of the oven,
Ceci & Bronfenbrenner, 1985).

*The remz
starting position for wea 1 became
<igit number compieted the call sign, anc initial are
from

to create 24 unique scenarios.

right to left, and half from lef to right. Although # is difficu’s zo i

Cuing Prospective Memory

Design. In each scenario, there were 25 aircraft.
The scenario began with three aircraft that were al-
ready flying, new aircraft appeared every 45 s thereaf-
ter. Only four of the 25 aircraft were the critical pianes
{those that were delayed and had their destination
changed), one each for Both Recrieval-only, Rehearsal-
only, and Neither. The ordering of these conditions
was rotated through the 6th, iith, 16th, and 21st
aircraft that appeared in a scenario. The critical air-
craft were spaced 3.75 minutes apart, so subjects had
one on its way before the next appeared. Nevertheless,
the load on prospective memory increased over the
course of the scenario because it took an average of
13.3 minutes to get an aircraft to its destination.

In addition to these four critical aircraft, there were
two aircraft that were delayed and their destination
was not changed, and two that had their destination
changed and were not delayed. They were randomly
assigned to the 5r>, Ith, 15th, and 20th positions ip
the scenario. The remaining 17 aircraft were nor
delayed and not changed. The non-critical aircraft
served to disguise the truce purposc of the experiment.
For all aircraft, the O signaled that the aircraft could
now fly. For the nondelayed aircsaft, the O appeared
when the strip highlighted; for the delayed aircraft,
the O appeared 150 s after the strip highlighted. Also,

notall the delayed planes required a destination change,

only the four critical aircraft.

Scenario construction. The base scenario was con-
structed as follows: A set of X, Y coordinates was
selected for each aircraft that specified its starting
position. Next, we selected a direction of flight (8
possible), initial speed (always medium), original des-
Unation (16 went to exits, 4 ro each, and 9 went to
airports, 5 to one and 4 to the other}, call sign (four
each of SWA, UAL, DAL, TWA, NWA, and five
AAL) with a three-digit number selected from 2 rendom
number table, and an initial altitude (either 2 of 3).
Twenty-four scenarios were constructed altogether 5

ANARQ* SDDS


Cuing Prospective Memory

ample, recall of a grocery list was better if subjects
made notes (an external cue) to help them remember,
even ifthe notes were not consulted at retrieval. Recall
was higher still when the notes were consulted. Is the
same true of prospective memory? If so, the Both
condition should set the upper bound on perfor-
mance. The Neither condition should set the lower
bound on perfczmance; subjects must rely solely on
internal aids.

If Retrieval-only performance is equivalent to Both,
and Rehearsal-only is equivalent to Neither, the exter-
nai cue must support primarily a retrieval function. If
Rehearsal-only performance is equivalent to Both,
and Retrieval-only is equivalent to Neither, the exter-
nal cue must support primarily a rehearsal function.
Advernatively, Retrieval-only and Rehearsal-only could
fall in-between the upper and lowes bounds, implying
that an external cue supports both functions.

In Experiment 1, Both, Retrieval-only, Rehearsa!-
only, and Neither were manipulated within-subjects.
Because subjects did not know how long the com-
mand would remain visible during the retention in-
terval, orwhether it would reappear, the use of different
rehearsal strategies should be minimized. Controlling
sehearsal and strategy in this way helped isolate avail-
ability of content as a causal factor.

EXpERIMENT 1

Method

Subjects. Subjects were recruited from the Univer-
sity of Oklahoma campus community aad paid $5 an
hour for their participation. Thirteen subjects partici-
pated for 12 days; eight participated for 6 days (after
having first completed 4 days in Experiment 2). Those
subjects for whom Experiment 1 was actually their

Figure 4.

The airspace, including Cour gates (A, 8, C, and DI, two airports (X and Y}, the column of

strips including cal! sign and prospective command, and the contro! area for changing

direction, speed, and altitude.

Boctronic. Control
aes sea
Radar display al AALS “) Divection
x
— Spcod
B
DB AALI23 8 M
— FAA J s
— oa ;
1
_ 2
: J} 3
—— 4
Landing
| Dives
| ef <<
. A
Airport N

Boundary


trackball. In addition, many updating functions will
be taken over by the computer. Although the high-
lighting of an electronic strip as a prospective re-
minder will be possible, it may be less effective than
the controller reaching up and offsetting the strip as is
done in the current system; highlighting would be
initiated through the keyboard, like so many other
routine actions. In the retrospective memory litera-
ture, it is well-known that memory is better for some-
thing you do as opposed to something done for you
(e.g., Slamecka & Graf, 1978); the same may be true
in prospective memory. There are reasons for concern
regarding automation, as well as opportunities to
make recommendations to improve the design of the
new system.

Vortac, Edwards, Fuller, and Manning (1993) com-
pared prospective memory performance in two groups
of controflers.? The Normalgroup controlled traffic as
they normally would. The Automation-Analog group
was forbidden from writing or manipulating the paper
strips; this group could only look at the strips. The
idea was that restricting interaction to looking only
would simulate the lost functionality resulting from
automation. At three different times during a scenario
a prospective request was made. A pilot requested an
altitude change or rerouting a couple minutes prior to
entering the controller's airspace. Because controllers
cannot unilaterally assume control of an aircraft out-
side of their assigned airspace, this created 2 natural
prospective memory request. The Automation-Ana-
log controllers granted more of the prospective re-
guests, and did so sooner, than the Normal controllers.
itis important to capitalize on this potential benefit of
“automation” to prospective memory by consic sting
how the new system should present external cues to
the controller.

Experimental design

The four ways that the availability of content will
be manipulated are: Both, Retrieval-only, Rehearsal-
only, and Neither.

Rehearsal and Retrieval (Both). If the external cue
is visible throughout the retention interval, both re-
hearsa! and retrieval are supported. If the goal is to

4In contrast to the present experiments, ATC
fidelity simulacor at the FA's Mixe Monroney Aeronautical C

Cuing Prospective Memory

return a library book by the end of the day, the Both
condition is akin to placing the book by the office
door where it is visible throughout the day (the reten-
tion interval) and when you leave (the opportunity to
execute the command). In the air traffic contro! situ-
ation, the controller would cncade a prospecrive com-
mand that would remain vis'ble throughout the
retention interval. This electronic strip would sup-
port rehearsal and retciewal because the controller
would be free to review/rehearse the information at
any time, and the information would be available at
the end of the retention interval.

Retrieval-only. Alternatively, the book could be
placed by the office door, but then your day is spent
in the lab, returning to the office just before heading
home. The book would not support rehearsal during
the day, but would be visible when you leave. The
controller could encode the prospective command
with an attached time delay (change the altitude on
American 123 in 2 mins}. Nothing would happen on
the electronic strip until the end of this time delay
when the prospective command would reappear. Al-
though the command could be rehearsed during the
retention interval, rehearsal would not be supported
by the external cue.

Rehearsal-only. The book could be visible through-
out the day but not when you leave. This would
happen if you spent most of the day in the office bur
depart for home from the lab. The controller would
encode the prospective command, which would re-
main visible on the electronic strip until sometime
prior tc when the command was to be executed. The
strip would support rehearsal, but it would not sup-
port retrieval because it was not visible at that time.

Neither. Finally, che book could be placed by the
office door but then the day is spent in the lab and you
depart from there. The controller would encode the
Prospective command, but it would never appear
again and the controller would rely solely on internal
memory aids. The electronic strip would support
neither rehearsat nor retrieval in this case.

Hypotheses. Incor:s-Peterson and Fourier (1986)
found that external cues supported both rehearsal and
eval Functions in retrospective memory. For ex-

too

Saas Weare


Cuing Prospective Memory

Figure 2.

llustrates the temporal availability of he prospective command for the Both, Retrieval-
only, Rehearsal-only, and Neither conditions. The timeline at the top of the figure
indicates the sequence of actions to be taken. Beginning at time 0 on the far left: A plane
appears, together with the appearance of its electronic strip (highlighted in blue). After
some variable time, the subject clicks the strip to reveal the prospective command. 150 s
after the plane appears, O appears. A click of the O initiates movement of the plane. The
retention interval is measured from the time that the strip is clicked (revealing the
command) until the O is clicked; the command can now be executed.

The timeline for the delayed-no change condition was similar except that when the
subject clicked the strip, no command appeared. The nondelayed-change condition was
just like the Both condition except that there was no delay between when the plane and
the O appeared. That is, the plane was ready to go when it appeared. Finally, the
nondelayed-no change condition was similar to the nondelayed-change condition except
that there was no destination change.

The horizontal bars at the bottom two-thirds of the figure indicate the temporal
availability of the prospective command for the four conditions of imerest (the filled
portion indicates when the command was present).

i 150 seconds j /



o>

1995031



Most of the errors involved sending aircraft to the
original destinations on the data biock. That is, if
subjects made an error, it was more likely to involve
forgetting that a prospective command was issued for
an aircraft (and sending it to the data block destina-
tion) than remembering that a command had been
issued but not remembering its contenc {and guessing
randomly among the five non-data-biock destina-
tions). However, this may have more to do with the
fact that the data block destination was the correct
destination 76% of the time.

The top panel of Figure 4 shows the proportion
sent to the correct destination over days. The data
were collapsed over adjacent days to smooth the

Cuing Prospective Memory

function. Because Day 1 was excluded, Day 12 was
combined with Days 10 and 11. Performance im-
proved in all conditions through Days 6-7. Beyond
that point performance was fairly stable. The learning
data show that the relative contributions of rehearsal
versus retrieval were unchanged by repetition over
days and increasing familiarity with the task.

The second dependent measure involved the crig-
ger: the time to click the O to get an aircraft flying.
Although no one ever forgot to do this, on occasion it
took over 100 s (means ranged from 17 to 28 s across
conditions). To ininimize the impact of the extreme
outliers, we conducted an ANOVA on the geometric
mean for each subject. We included both critical {the

Figure 4.

Proportion seni to the correct destination by days. The B represents the Both condition, R

the Retrieval-only condition, r the Rehearsal-only condition, and N the Neither condition.
Experiment 1 data are given in the top panel, Experiment 2 data in the bottom panel.

Experiment 1
10 ;
os 4 es <<
E Cy) ae
fe ae |
i
a
° |
09 -t T T TT T i
9 2 4 6 8 19 12
to Experiment 2
° aS
pr) |
H |
a6 4
§
g a4 SBoth |
& a2 -! > Retevai-ony i
F + Rehcersalonty |
{ |
Nether t
oo + - : 7 i i
() 2 4 8 10 12

q,


Cuing Prospective Memory

Figure 3.

Proportion sent to the correct destination. Experiment 1 data are given in the left-hand

panel, Experiment 2 data in the right-hand panel. The Retriev |-only condition is
abbreviated Retr and the Rehearsal-anly condition is abbreviated Reh.

Experiment 1

Proportion correct

Experiment 2

Results and Discussion
On the first day, subjects were interrupted fre-
quently by the experimenter and ren:
to proceed. Therefore. we counied the first day as
practice and — duded ir from the analysis. We exam-
ined datat , sor those retention intervals between
G60 co 240 s. which accounted for berter than 93% of
the daza.* One subject was excluded because more
than 30% of aircraf: failed to get to 2 destination.
The feft-hand panel of Figure 3 gives the proportion
of aircrafi sent to the Correct destination for the Bath,
euieval-only, Rehearsai-only. and Neither conditions.
Performance in ali conditions was significantly zbove

ded about how

chance {or 1/6, smalles: s {19} > 5.50}. A one-way

3

P< G5, Pairwise rests were conducted controlling & az
-OS/aumber of comparisons. They showed thar the ex-
ternal cue supported primsrily a retrieval function: the
Buck and Retrieval-only conditions di
borh were beter than the Neither condition. The Both
condition was also berrer than Rehearsal-only condition;
the Retrieval-only condition was marginally better than
the Rehearsal-ealy condition (7 (193 = 2.62, p<-02). The
Rehearsa!-only and Neither conditions did nor differ.

‘The proportion that crashed and failed to reach any
destination, of were still dying at the conclusion of the
scenatic both resulted in missing data. We combined
these categories (called StillCsash). The ScillCrash cat-
egory occurred rarely {Mi < 4.6%) and did not vary with
condition, F{6, 135) < 1.0, 34S_~ .004,

no: differ, and



second ‘experiment performed better overall than the
other subjects, but the parcern of results was the same
for both groups.

The air taffic control simulation. The experiment
was conducted on microcomputers that ran the FAA’s
Air Traffic Scenario Test (Aerospace Sciences Inc.,
1991). This simulation was a modified version of a
test used by the FAA to screen applicants for air traftic
controller positions. The simulation captures many of
the major activities included in air traffic control and
provided a rich environment in which to explore
prospective memory. Figure 1 illustraces the screen
display of the simulation, which consists of a radar
display or airspace (far left), and an aircraft control
area (far right). The modification we added to the
original softwary was the column of electronic strips
berween the airspace and the aircraft control area.

The airspace consisted of four exits out of the
airspace (labeled A, B, C, and .D) and two airports (X
and Y). Aircraft were represented in the airspace by a
cali sign (an alphanumeric identifier like AAL123), a
directional arrow, and a data block. The data block,
which moved as the aircraft moved, displayed the
aircraft’s speed (Fast, Medium, or Slow), altitude (1-
low to 4-high), and destination (airport or exit).
Aircraft AAL123 is illustrated in Figure 1, flying at
Fast speed, altitude 4, rowards its original destination
atA.

The electronic strip for AAL123 is also ilustrated.
The second line of a strip is where the prospective
command was displayed; it shows a change to the
original destination (GO TO X). The original desti-
nation remained visible on the data black; the elec-
tronic strip was the only place to ger information
regarding the changed destination.

Procedure. Subjects began by observing the Ex-
perimenter contro} a five-minute practice scenario.
The subjects then completed the practice scenario
themselves, Subjects completed two 22-minute sce-
narios per day, The assignment of scenario to subject
was counterbalanced, and no subject ever completed
the same scenario twice.

Cuing Prospective Memory

The rules of the simulation were: 1) aircraft must
exit a gate high and fast, 2) aircraft must tand at an
airport low and slow, and in the correct direction (the
arrow at the bottom right-hand corner of Figure 1
indicated the landing direction), 3) aircraft could not
overfly airports, but could overfly each other if they
were at different altitudes, 4) aircraft had to remain
separated from each other and the airspace bound-
aries, and 5) subjects should be as efficient as possible
(ie., get an aircraft to its destination as quickly as
possible}.

Interaction with the simulation was accomplished
with a mouse. When a change to an aircraft’s direction
of flight, speed, or altitude was desired. the mouse was
moved over the aircraft and clicked, thereby selecting
the aircraft. Then the mouse was moved to the aircraft
control area and a new direction of flight, speed, or
altitude was selected.

Figure 2 is a timeline of actions that illustiates how
the prospective command was presented. Whenever a
new aircraft appeared on the sczeen, the accompany-
ing electronic strip appeared at the same time, high-
lighted in biue, with only the call sign visible. The
subject was instructed to click the strip as soon as
possible, whereupon the strip would return to its
normal white on black and reveal a prospective com-
mand (if the aircraft were a critical plane). Note that
the 150 s that elapsed between when an aircraft
appeared with the strip highlighted to the cime that
the plane was able to fly, was for the subset of aircraft
related to the prospective manipulation. (Subjects
had been told during the instructions that the delay
was to allow threatening weather to clear.) After 150
s, asmall circle (O) appeared next to the dara block (as
did a non zero altitude). A click of the O initiated
aircraft movement. Nothing on the strip could serve
as a trigger, only the O next to the dara block.

For the Both, Retrieval-only, Rehearsa!-only, and
Neither conditions, clicking the strip revealed a pro-
spective command in the form of a changed destina-
tion. The prospective command was visible for the
next 16 s. In the Neither condition, the command



FUNCTIONS OF EXTE

The sex

sense ther has dominated research in psychology for

se of memory commonly evoked and t

over a century is retrospective memory. or memory for
is usu-

past events. The use of retrospective memory
ally prefaced by the remark, “Remember when....”
Howeves, memory is also often used to rernember to

do things in the future. This can range from remem-
bering to turn off the iron, remembering to pick-up

grandma at the airpors. to remembering to take medi-

ind of memory hay been termed pro-
spective memory by Badérley and Wilkins (1984) and
Meacham and Leiman (1982). The use of prospective
memory is esually prefaced by the remarx, “Don's

cation. This ki

forget to.

Following Einstein and McDaniel (19903,
vide prospective memory intc two componer

we di-
Onc
trigger that initiates the prospective

component is the
action; the other is the

cnggered. For example. if the task is to pass along 2
phone message to a colleague, secing the colleag
. Both

ise memory ta be successful,

uz of the action thar is

car

cis

the trigger; the content is the relayed message.

are required for prospec
Forgetting to stop at the grocery store on the way
home but remembering what was to be purchased is

unsatisfactory. Likewise, remembering that you have

2 message for a colleague but ror remembering the

message content is unsatisfactory.

rast

al cues are pe!

In prospective memory. exten
(or a review see Harris, 1984). They zre even com-

mere

ly available. including a pill alarm. a whis

teapot, or a headlight alert, to name a
Herrmann, Burrows, & Moore, 1991}. Ex
support successful performance of prospective actions

ternal cues

in one of ewo way:

An external cue 2am SUE
component of prospective memo

port pri

by the door as 2 reminder to return an overdus book

to the library, setang the alarm on your watch or

A trigger cue
the time to take an action. bur

proclaims ther now

it does not indicate what that action is. For example,
Meacham and Leiman (1982; Meacham & Singer.

1977) bad subjects recurn postcards at various dates in
the future. Half the subjects were given colored rags to

tects with

pur on their key chains as a reminder. Su
tags (external cues} did berter than those without tags.
The tags signaled that something was to be done, but
d not indicate what that something was.

A second way thar externa! cues can support pro-
spective memory is by combining the uigger and
content components iplacing running shoes by the
door to emember co take them to work. taping a note
on the computer sereen with 2 reminder to pick up
bread on the way home}. A combined cue proc!aims
chat it is time to take the action as well as what the
action should be. Meacham and Columbo {1980:
instructed children to remind the experimenter w
open a surprise boxwhen the experi
The box was placed out of sight and half the childre!
temincer,

was fini

were given 3 clown to use as 2 and in-

structed how co use it.
because ic v

ne clown served as 2 trigger

visible at the conclusion of the rete

don interval (the end of the experumenti. The clown
also served to remind the children of the content fro
The externa!

view the surprise box}. cue was effective:

more of the children who got the clows as 2 reminder

arked to sce the surprise box.

The Meacham and Columbo {1980} experiment
illustrates the problem that motivates the current
research. Because the clown was present throughout

the retention interval, subjects could remem!

tox
1) The
ciown could support rehearsal of the concent during

for the surprise box for either of twa reason.

the retention interval (ie. rehearsal of asking to see

the surprise box later}; 2) the clawn could support

retrieval of the content {i.e., retrieval of asking for the

surprise box) at the end of the retention interval

: twa funcdions are naturally confeunde
pr
ant to know to what e

T

external cue
vel W

We

nt thraugnour a retention i

mt successful



Neither condition was difficult and tried harder to
succeed. The Rehearsal-only subjects, on che other
hand, might have become increasingly frustrated at
their inability to perform beter at 2
have perceived as relatively easy.

An ANOVA on the geomeiric mean time to click O
was not significant (F{3, 55} < 1). (We excluded the
deiayed-no change. nondelayed-change, aad
nordelaved-no change conditions because the; were
manipulated within-subjects.) The time to respond to
the trigger was not affected by manipulations of the
availability of concent. The ANOVA on the geomerric
mean time to click the highlighted strip was not
significant (A3. $53 = 1.52). Either time to click the
highlighzed strip w2s not a sens:
load, of subjecis had no mo-e trouble with the diffi-

task they may

ve Measuie vi WOrK-

cult conditions {¢.g., Neither} than with the easier
conditions (e.g., Both}.

The findings of Experiment 2 parallel those of
Experiment 1; the external cue supports primarily a
retzieval function. Apparently, allowing the opportu-
nity to tailor rehearsal and retrieval strategics to the
way the extcrnal cue was presented made little differ-
ence. The retrieval function of the external cue was

primary and was not affecte: by differential rehearsal

2

and retrieval strategies.

GENERAL Discussion

Two experiments Cemonstrated that external cues
support a retrieval function. In a simulated air traffic
contro} cask, it is importance thac an cxternal cue that
provides content be
d can be execured. Having the exter-

visible at the time that the pro-

spective comm

nal cue visible during the retention interval was no
more effective chan not having the cue visible ar all.
‘The benefit ro rhe Both and Retrieval-only conditions
was visible from the outset of training, and remained
over the course of training. We also found that chese
manipulations of content did not affect the latency of
an a.tion being wiggered, although this may have
something ro do with this being an event-based task.
When subjects conld railor their encoding and

retrieval strategies to the cues {Experiment 2), chere
was a potential ceiling effec: for the Both condition

over the las: three days of training. If this was a real

Cuing Prospective Memory

ceiling effect,
best of ail, implying a potential benefit of both re-
hearsal anc: retrieval in thar conditi
fact thar the Rehearsal-only condition was wozse than
the Neither condition (and getting worse with train-
ing) suggests that zchearsal was of little help; the Both
and Retrieval-only conditions may have continued to
perform equivalently, even after the porential ceiling

ion. However, the

effect was eliminated.

The external cue presented in the current experi-
ments was very explicie. In fact, it reiterated che
original prospective command (GC TO X)}. As such.
the external cue was not strictly speaking a memory
cae in the Both and Retrieval-arly conditions. If the
subjects remembered to look at the proper sip {as-
suming vnat they could not remember
tion unassisted),
have presented the command initially, and then ma-
Nipulated the remporai availabiliry of a less expliciz
cue ic.g., the word CILANGE razher than GO TO X3.
Subjects would not perform as accurately in this
modified experiment. However, we would expect the
same pattern of results (Both = Retrieval-oniy > Re-
hearsal-only = Neither} if we scored the data as fol-
lows: Correcsif plane zo: sent to its original data block
destination, Wrongif plane sent to original data block
destination. That is, Correez means that subjects knew

informa-

the command wes there. We could

to make a change (the data block destination was
wrong). Having no idea what rhe correct destination
was, however, they could only guess among the five
remaining destinations.

How general is the conclusion that externa! cues
support primarily a retrieval function? What circum-
stances might produce a different resule? We consider
several mirigaring factors which, in = different situa-
ton, could resuit in differentconclusions being drawn.

The relationship between the Both and Retieval-
only conditions may depend on the distinctiveness of
the cue (McDaniel & . 1993, showed that
distinctive cues were better than nundistinctive cues}.
For example, che success of the Both condition may
depend on whether subjects habicaare to a continu-

ously available cue. Stepping over a 10-be-returned
library book throughaut the course of the day may
incre:

the likelihoad thar you will simply step over

it yet again on your way home. Conversely, the success

ADA291932


ai

Drew, G. C. (1940). An experimental study of mental
fatigue. British Air Ministry, Flying Personnel Re-
search Committee Paper No. 277.

Einstein, G. O., & McDaniel, M. A. (1990). Normal
aging and prospective memory. Journal of Experi-
mental Ps ches + Learning, Memory, and Cogni-
sion, 16, 717-726,

Harris, J. E. 984. Remembering to do things: A
forgotten topic. In J. E. Haris & P. E. Morris
{Eds.), Everyday memory, actions, and abeens-
mindednese. London, England: Academic Press.

Hopkin, V. D. (1988). Human factors aspects of the
AERA 2 program. Farnborough, Hampshire, UK:
Royal Air Force Institute of Aviation Medicine.

Intons-Peterson, M. J., & Fournier, }. (3986). External
and internal memory ow often do we use
them? Journal of Experimental Psychology: General,

15, 267-280.

sucks A. (19893. The
(Human Facvors
UK: Royal Signal and Radar Establishment.

McDaniel, M. A. & Einstein, G. O. (1993). The
importance of cue jarity and cue distinctive-
ness in prospective memory. Memery, 1, 23-41.

Meacham, J. A. & Colombo, J. A. (198). External
retrieval cues facilitare prospective remembering
in children. Journal of Educational Research, 73,
299-3C1.

Meacham, J. A. & Leiman, B. {1982}. Remembering to
perform future actions. In U. Neisser (Ed.}, Memory
observed: Remembering in natural context (pp. 327-
336). San Francisco: Freeman.

Meacham, J. A. & Singer. J. (1977). Incentive effects in
prospective remembering. The Joumat of Psychot-
ogy, 97. 11-197.

‘CUS. GOVERNMENT PRINTING OFFICE: 1945 - 660-067/00093

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Petro, S. J., Hermann,
M. (1991). Usefulness of cornmercial memory
aids as a function of age. /rternazional Journal of
Aging and Human Development, 33, 295-309.

Rubin, T. (1988). User interface design for computer
systems, Chichester, West Sussex, England: Ellis
Horwood Limited.

Slamecka, N. J., & Graf, P. (1978). The generation
effect: Delineation of a phenomenon. /oxrnal of
Experimental Psychology: Human Learning and
Memory, 4, 592-604.

Vortac, O. U. (1993). Should Hal open the pod bay
doors? An argument for modular zutomation. In
D. J. Garland & J. A. Wise (Eds.}. Human factors
and advanced aviation technologies. Daytona Beach,
Florida: Embry-Riddle Aerenautical University
Press.

Vortac. O. UL. Edwards, M. B.. Fuller, D. K., & Man-
ning, C. A. {1993}. Automation and cog:
air traffic contro): An empirical investigation. 4p-
plied Cognitive Psychology, ?. 631-651.

Vortac, ©. U.. & Gerrys, C. F. (19903. Cognitive faxctar:
in the use of flight progres: strips: In
automation. Cognitive Processes: Laborato:
ing Paper, University of Oklahoma, Norman, OK.

Wrest, R. 11988). Prospective memory and aging. In M.
M. Gruncberg, P.E. Morris, & R. N. Sykes (Eds.},
Practical aspects of memory: Currenz research and
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Wilkins, A. J., & Baddeley, A. 1D. (1978). Remembering
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Emory.

ADA291932


ACKNOWLEDGMENTS

O. U, Vortac represents the collaborative efforts of Francis T. Durso, Scatt D. Groniund. and
Stephan Lewandowsky, all of the Department of Psychology, University of Oxlahoma, Norman, OK

73019 (Email: sgroniund@uoknor.edu).

This work was supported by Contract DTFA-02-91-C-91089. Thanks to Bob Blanchard, Bill
Collins, Doug Herrmann, Paula Hertel, Mark Rodgers, Dave Schroeder, Earl Stein, Mike Wayda, and

especially the reviewers and action editor, for edifring comments on catlicr versions of this manuscript.

oi
We express our appreciacion to Dusty Godwin, Allen Molloy, Leslie Wiggins, and Russ Brown, for their

fine efforts on chis project.

i



Technical Report Documentation

{ 4. Report No. 2. Goverment Accession No.

DOT/FAA/AM-95/9

3. Rec'pient's Ca‘aica No.

4, Tas and Subtre

Automation and Cognition in Air Traffic Control:
An Empirical Investigation

5. Repent Date

February 1995

8. Pertorming Ormganzaven Cose

7, Author's}
O.U. Vorzac, Mark B. Edwards, Dana K. Fuller. and
Carol A. Manning

B. Petorming Organ zeton Repor Mc.

2) Performer
FAA Civil Aeromedical Instiruce
P.O. Box 25082

Oklahoma Cirr, OK 73125

‘ganization Nare

devas

University of Oklahoma Dept. of Psychology
755 W’. Lindsey, Room 705
Norman, OK_ 73619-0535

19. Woe UTENG. RAS)

11 Cantante: Gant

DTFA-02-91-C-91089

42 Seanse" Sy came anc Ax
FAA Office of Aviation Medicine
Federal Aviation Administration
800 Independence Avenue, SW’.
Washington. DC 20591

FAA Research and Development Service
Federai Aviation Administration

800 Independence Avenue, $.W,.
Washington. DC 20591

13. Type of Reyer ars Peres Covers

15, Sucsiemen’ 5

16 Abstract

A simulation of an air traffic control task was the seiting
cues in prospective memory. External cues can support u

externa! cue to disentangle awo possible functions the cu
retention interval could support rehearsal of rhe

of the action. We focused cn memory for che content and manipulated the semporal cha’

be-per
end of a retention interval could seppart retrieval of f the to-be-performed action. Two experiments were
conducied that converge on the same conclusien: the primary function of an external cue was io §:
retrieval. Implicat:ons for the de: ign of a computer inserface to present prospective cues arc

¢ ior an investigation of the functions of exzerni!
he triggering of an action or memory for the content
ics of the
ible ducing 3
thle ac the

racteris
¢ can support: 1) An external cue ¥
emed action: 2} An external cue

discussed

WT Key Words
Automation, Air Traffic Centro}.
Flight Progress Data, Cognitive

Psychology, Memory, App

76. Dusizute> Staterent

Document is available ro the public through the
National Technical Information Service,
Springfield. Virginia 22161

72, Securty Classt ‘c ths vepe—- ar
Unclassified

t classified

Form DOT F 1790.7

Repreducton ct ecmpieres pa:



Cxuing Prospective Memory

four delayed-change conditions—Both, Rei
Rehearsal -on aly, d Neither) and non-critical
and

ce among conditions, F(6, 135) = 1.96, p> .05,
317.7. The ume to respond to the trigger was
aot affected by manipulations of the availability of

content. An indirect measure of workload was also
computed by determining how quickly a subject clicked
a highlighted strip. Again. geometic means were
used. and again, no significant difference was found
among conditions, /(6, 135} < 1. p>.1, AfS_= 283.6.

In sum, Experiment 1 showed that an external cue
supported a retrieval function. Making the prospec-
mand visible during che rez

tive com ation intervai

was no better than neve: making it v’ after an
ai encoding period of 16 s. Wii! the same be true
when rehearsal and retrieval strategies ere unencum-
dered?

In Experiment: 2. subjects were allowed re concen-
tate on a single method for presenting prospective
cosmmands. That way, differential rehearsa! and re-
irieval strategies could be used in conjunction wi
the methed of cue presentation to optimize perfor-
mance. Perhaps subjects compensate in the Re-
hearsal-only and Neither conditions by using 2 more
eleborative rehcarsal straregy. The cognis
this may have been coo great in Experiment ?, or che
benefit tou small: more claborate strategies might be
worth che cffort in Experiment 2.

<e cost of

EXPERIMENT 2

The only change from Experi
Both, Retricval-only, Rehearsal-only, and Neither
conditions were manipulated berween-subjeczs. This
allowed subjects to optimize rchearsel and retrieval

strategies.

Method

Subjects. Subjects were recruited from the Univer-
sity of Oktshome campus come yand were paid
$5 an hour, or received experimental credi
satist¥!

g 2 course requirement, in excha

pan: ipated for 6

:pation. Forty-four sud}

days: 13 participated for only 4 davs {due ta a sched-
uling mix-up}. Three subjeces were excluded because
over 30'
Procedure. Both, Retrievai-o.
and Neither were manipulazed be
jects were raademiy assigned to one of the fo:
duiions (Nga, 7 14,4 Npeneve!
2 14). Wes

% of aircraft never reached a destination.
Rehearsal-only,

en subjects; sub-

Results and
\ + counted the first day 2s practice and cacluded
lysis. We exam: ed dara only for those

it from the en
retention intervals between +0 to 246 5 better than
94% of the woral!

‘The right-hand panci of Figure 3 gives the propor-
tion of aircraft sent to the Carsecz destination. Perfoz-
mance in every condition wis above chance (1/6,
smallest 7 (13) > 3.0). A one-way ANOVA on the
Both. Retrieval-only, Reheassal-only, and Neith

conditions showed a significant effect of condition
143, 30) = 6.56, MS, = 38. p<. 05). (The delayed-
no change, nondelayed-change, and nondelayed-no
change conditions were exciuded because they were
manipulated within-subjects.) The Ryan multiple-
range test controlling @ at .0S/number of compari-
sons showed that the Both. condition was better than

Reheassal ents and Neither, and Retrieval-oniv was
an Rehearsal-only. The Both and Retrieval-
"conditions did nor differ, nor did the Rehearsal-
ather conditions. The StiliCresh category
24} and did not vary accass

only

id rarely (
conditions (F< i}.
the

The bosom pane! of Figure 4 shows the Correct

caregory over days. Day 1 was cacluded. Performance

improved through day 5: beyond thar it appears that
Both and Retrieval-only performance was stabilizing,
although stabilization of the Both dats may he =
ceiling effect. Note that the means for Days 5 and 6
represent a subset of subjects comprising the means
for the previous days. Performance in the

either
condition seemed to be improving with practice,
while performance

in the Rehearsal-only condition

dtu be worsening (although :! was based

five subjects:

Perhaps subjects sensed thar the



Cuing Prospective Memory

of the Retrieval-only condition may depend on the
atcention-grabbing ability of the external cues when it
ears. In che present experiments, we decided to

rea,

not make the return of the esternal cue conspicuous.
Ch

Uaat

ly. a Retrieval-only cue could be designed such

ecaewould never be missed (reappears

Such acue could ser
of the

about this when we

the caters

depends on the wpe of rehearsal
RCon inter M

aid rezruspecii

pntenance 5

Subj cts ts had the op-
ze tailor their rehearsal te be maximally
and performance did aot
tion. The abilicy
e rehearsal may be workload

effective in F:

periment

improve retative te the Neither con

to make use of elaborat

erfornance o: the air traffic control
have begun to suffe: if subjects tried

tive rehearsal strategies. Inde

dependent:
sim

ation mz

mors clabor. -d, the cask

fficuls. although ic became easi

was fairl
d. If this improvement was accompanied by 2
decrease in weorklead, we mi
the Rehea

In fact. the opposite occurred.

over

have expected co see

rsal-oniy condition improve v

4

h sraining.

The results of Vortac et al. £1993) implied thar
aztomation may benefit prospe
present results are 2 first Joos at how ex:ernal cues

e memory. The

might be presented to take advantage of the aurom:
n. However. which is to be preferred: havin
e al cue pres
val. or only when itis needed? What additional factors
might lead an interface design hoose ene method
of presenting, cues aver the other?

he final design of a
involves many tradeoffs {see Rubin, 1988

throughout the retention inrer-

rate

suman-compurer

ample. if deasiry of information is a problem, it mar
be preferable co implem
Retrieval-only cundation: the
for tess time. In addition, a jate-ietura

creen

in che Retrieval-only condition could be made two de
novel and therefore grab attention. An exicrnal cuc
that grabs attention (or sounds a warning) might seem
like a good feature, but not if the user's attention is
taken away from a more imporiant task, or taken away
at an inopportune time. On the other hand. if work-
load isa limiting factor, ch:
a time tag to the Rerrieval-only condition might be
to simply make the

. extra time spent attaching

too costly and it might be detter

cue available ior the whoie time. However, the user

ther runs the risk of habituating to the constan

present cue

The present 4
confounded functions of,
and retrieval. We used a tas!

ch succeeded in disenrangl:

externa! cues, rehearsal

of obvious relevance ta

affic controilers, although we suspect that the
sions hold for anyone who work
complex dynamic envizonment that puts a strain on
y cognitive funcrion-

in 2 hight

ry. Our ev

st such an environmen.

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