M E M O R Y , 1 9 9 8 , 6 (4 ), 4 5 5 ±4 6 5
F o r w a r d T e le sc o p in g : T h e Q u e s tio n M a tte r s
V in c e n t P ro h a sk a
L e hm a n C o lleg e , T h e C ity U niv er sity o f N e w Y ork , U S A
N o rm a n R . B ro w n
U niv ersity o f A lb erta , C an a d a
R o b e rt F . B e lli
U n ive rsity o f M ic h ig a n , U S A
F o rw a rd tele sc op ing , th e r ep o rtin g or da tin g o f e v e nts a s b e in g m or e re c en t th an
th e y a c tu a lly w e re , is o fte n o b se rv e d in s u rv ey s a n d p ro d u ce s in ac c ur a te d ata . W e
be lie v e th a t s om e fo rw a rd tele sc o ping o c cu r s w h e n th e q ue st io n fo r m a t a llo w s
pe o ple to re s p o n d w ith ou t ex ten si v e r etrie va l o f te m p o ra l inf o rm a tio n co n ce r ning
th e ta rg e t e v e nts. W e c o lle c te d tw o typ e s o f da ta . T he f irst , th e typ e u su ally
co lle c te d b y su rv e y r es ea r ch e rs , in v olv ed v isits to m e dic al do c to rs . A s is c o m m on
in s ur ve y r es e ar ch , th e a ctu al d a te s o f the e v e n ts w e re n o t ve r ifia ble . T h e s ec o nd
ty p e in v olv ed s tu d en ts ’ pa r ticip atio n in la b o ra to ry r e se ar c h st ud ies . H e re , th e
ac tua l d a tes w er e v er ifia b le . W e d em o n st ra te th at m o dify ing the q u es tion s as k ed
pr od u c ed d iffe re n ce s in the a m o u n t o f f o rw a rd te le s co p in g in p a rtic ipa n ts ’
re sp o ns es .
INTRODUCTION
``H a v e y ou b ee n tre a te d b y a m ed ica l d o cto r d u rin g th e la st six m o n ths? ’ ’ ``O n
w ha t d ate d id y o u bu y y ou r h om e c o m p u ter? ’ ’ ``S inc e th e b e g in n in g o f th is y e ar,
h av e y o u b ee n th e v ictim o f a c rim e? ’ ’ ``W h en d id y o u la st try to sto p sm o k in g? ’ ’
Q ue stio n s su ch as th ese are co m m o n ly a ske d on a v a rie ty o f surv e y s to
asc e rta in th e p re v a le n ce a n d fre q u en c ie s o f su c h ev en ts, an d to m a k e de c isio n s
ab o u t th e a llo c atio n o f n ee d ed re sou rce s. Su c h qu e stio n s are also o f in tere st to
m e m o ry re sea rch e rs, e sp ec ially th o se c on c ern e d w ith h o w tem po ra l in fo rm a tio n
is rep re se nte d an d re trie v ed . P rio r in v e stig ato rs ha v e fou n d th at pe o ple ’ s
R e q u e s ts fo r re p rin ts s h o u ld b e s e n t to V in c e n t P ro h a s k a, D e p a rt m e n t o f P s y c h o l o g y , L e h m an
C o lle g e , 2 5 0 W . B e d fo r d P a rk B lv d ., B ro n x , N Y , 1 0 4 6 8 ±1 5 8 9 , U S A . E m a i l:
v i n c e n tp @ a lp h a .l eh m a n .c u n y .e d u
T h is re se a rc h w a s s u p p o rte d b y a n o p e ra ti n g g ra n t fr o m th e N a tu ra l S c ie n c es & E n g in e e rin g
R e s e arc h C o u n c il o f C a n ad a a n d b y a g ra n t fro m
th e N at io n a l In st itu te o f M e n t a l H e a lth
#R 24 M H 4 974 7 .
Ó
1 9 9 8 P s y ch o lo g y P re s s L td
456
PROHASKA, BROWN, BELLI
re sp o n ses to th ese qu e stio n s o fte n c o nta in a p a rtic u la r fo rm o f e rror ca lle d
``fo rw a rd te lesc o pin g ’ ’ . Fo rw ard te lesc o p in g is th e re p orting o f e ve n ts a s h a vin g
oc c urre d m o re re ce n tly tha n th e y a c tua lly o c cu rred . F o r ex a m p le , if a resp o n d en t
say s ``Y es’ ’ to visitin g a d o cto r du rin g th e la st six m on ths, w h en a ctu ally th e la st
visit w a s e ig h t m o nth s a go , o r rep o rts c o m p letin g a m a jo r h o m e re p a ir d u rin g
M a y , w h e n th e re p a ir w a s ac tua lly c o m p lete d d u rin g A p ril, th e re p o rt h a s b ee n
fo rw ar d te le sc op e d. F o rw ard tele sco p ing e rrors a re c o m m on w h en e v er p e o ple
an sw e r q ue stion s ab o ut w he n a uto b iog ra ph ic al e v en ts o c cu rred (e .g . C oh e n &
Jav a , 19 9 5 ; H u tte n lo ch e r, H ed ge s, & P ro ha sk a , 1 9 8 8 ; L o ftu s & M a rbu rg er,
19 8 3 ; M ea n s & L o ftu s, 1 9 9 1 ; N eter & W a ks be rg , 1 9 6 4; R u b in & B a d d eley ,
19 8 9 ; T h o m p so n , S k o w ro n sk i, & L e e, 1 9 88 ). O u r h y p oth esis is th at th e d e g re e
of fo rw a rd te le sc o pin g is asso c ia ted w ith th e fo rm o f th e q ue stion tha t
re sp o n de n ts a re ask e d. W e m o re fu lly de v elo p th is h yp o th esis la te r, afte r
co n sid ering th e ev id en c e of fo rw ard tele sc op in g an d the ro le o f re co n struc tio n in
an sw e rin g qu e stio n s ab o u t th e tim e of e ve n ts.
T h e co m m o n e v id e nc e o f fo rw a rd te le sco p in g c on sists o f d iffe ren c es in th e
nu m b er o f re po rts be tw e e n g ro up s . F or e xa m p le, L o ftus a nd M arb u rge r (19 8 3 )
ask e d p e op le w h e the r th ey h ad b ee n th e v ictim s o f crim e s d urin g a six -m o n th
re fe ren c e p e rio d . O n e g ro u p w as g iv en a n ex p lic it la nd m ark o n w h ic h th e
re fe ren c e p erio d b eg a n (th e e rup tion o f M t. S t. H e len s o r N e w Y e ars D ay ) w h ile
th e o th er w as n ot (i.e. ``d u rin g th e la st six m on ths’ ’ ). T h e g rou p w itho ut th e
la n d m a rk rep o rte d m o re in sta nc e s o f crim e v ictim isa tio n . L o ftus an d M a rb u rg e r
co n clu d ed tha t w ith o u t th e p rese n ce of a lan d m ark , e ve n ts th at ac tu a lly oc c urre d
be fo re th e re fe re nc e p e rio d w ere fo rw ar d te le sc op e d in to it.
N e ter a n d W a k sb erg (1 9 64 ) c o m p a red p e o ple ’ s rep o rts o f m a jo r ho u se ho ld
re p a irs an d pu rch a ses u sin g eithe r un b o un d e d o r b o u nd e d re fere nc e p erio d s. T h e
sam e re sp on d en ts w ere in terv ie w e d in se p ara te w av e s o f d ata c o lle ctio n tha t
oc c urre d six m o n ths ap a rt. In th e u n bo u n d ed c on d itio n , th ey w ere sim p ly to ld to
in d ic a te e ve n ts sin c e th eir last in terv ie w . In th e b o un d e d co n dition , th e
in terv iew e r first re a d th e ite m s rep o rte d at th e la st in te rv iew , a nd th en ask e d fo r
ne w ite m s. N e te r a nd W a k sb erg fo u n d th at m o re ite m s w ere re p orte d in th e
un b o u n de d in te rv ie w s. T h ey co n clu d ed th a t in th e u n bo u n de d in terv iew s,
pre v io u sly re p orte d item s w e re b e in g fo rw a rd te le sc o pe d in to th e c u rren t
re fe ren c e p erio d .
F in ally , B ac h m a n a n d O ’ M alley (1 9 81 ) ask e d h ig h sc h oo l stu d e nts a bo u t
th e ir dru g u se o v er re fere n ce p e rio d s o f d iffe ren t len g th s (e.g . th e pa st y ea r, th e
pa st m o n th ). B ac h m a n a n d O ’ M a lle y fo u nd tha t sh o rte r refe re n c e p erio ds
pro d uc e d relativ ely h ig h e r usa g e ra tes. A lth o ug h the y co n clu d ed th at lo ng e r
re fe ren c e pe riod s le d to u n d ere stim atio n o f d rug u sag e , th e y a lso no te d tha t
fo rw ar d te lesc o pin g o f e arlie r e v en ts o f dru g u sag e c o uld b e in flatin g th e
estim a tes in th e sh o rter p erio ds.
T h e in te rp re ta tio n o f e v ide n c e o f fo rw ard tele sc o p in g is p ro b le m a tic,
ho w e v er. O bse rv e d d iffe re n ce s in th e nu m b er of re p orts a c ro ss d iffe ren t
FORWARD TELESCOPING AND QUESTION FORMAT
457
refe ren c e p erio ds m ay or m a y n o t in dic ate th e p rese n ce o f fo rw a rd te le sco p in g.
A s S ud m an an d B ra d b urn (1 97 3 ) no te d, it is p o ssible th a t p e op le a re fo rge ttin g
ea rlie r e v en ts a n d b e in g m or e ac cu ra te in th e sh o rte r an d m ore re ce n t re fere n ce
p eriod s (th e e x pla na tio n fav o ure d b y B a ch m a n & O ’ M alley , 1 9 81 ). In o rde r to
d eterm ine th e p re sen c e of fo rw ard te le sc op in g , v erific a tio n o f p eo p le ’ s re p orts is
n ec essa ry . F o rtun a tely , so m e rec e n t stu d ie s h a ve b e en a ble to e x am in e fo rw a rd
telesc o p in g u sin g ev e n ts w h o se d ate s ca n b e v erifie d .
In a ve rific atio n stu d y , H u tten lo ch er et al. (1 9 8 8) p ro v ide d e v id e nc e fo r
g rea te r ac c u ra c y in sh o rte r re fe re n c e p e rio d s. H u tte n lo c h e r et a l. a sk e d
u niv ersity stu de n ts to list film s th e y h a d a tten d e d a t th e ir u niv e rsity ’ s film
so cietie s. T w o re fe re n ce p e rio d s w e re use d , the e n tire a ca d em ic ye a r a nd th e
m o st re ce n t ac ad e m ic q u arter. R e sults sh o w e d th at stu d en ts a sk ed o n ly ab o ut th e
m o st re c en t qu a rte r rep o rte d a tte n din g m o re film s d urin g th at q ua rte r th a n d id
stud e nts a sk ed a bo u t th e en tire y ea r. W ith ou t v erifica tio n d a ta, th is fin d ing c ou ld
b e in terp rete d as ev id en c e of fo rw ar d te le sc o pin g in th e sh orte r re fe ren c e pe rio d.
H ow e v e r, H u tte n lo c he r e t al. fo u n d w h en c o m p a rin g rep o rts to ac tu al film d ate s
tha t the d iffe re n ce in the n u m b e r o f rep o rts b etw ee n th e g ro u p s w a s n o t d ue to
telesc o p in g . T h at is, fo rw a rd te lesc o p in g w as p res en t in b o th g rou p s, b u t
p artic ipa n ts in th e sh o rte r re fe ren c e p erio d c o nd itio n re p orte d m o re ev e n ts tha t
ac tua lly o c cu rre d d u rin g th a t re fere n ce p erio d . H u tte nlo c he r et al. co n clu d ed tha t
the sh orte r refe ren c e p e rio d led p e o ple to c o nd u c t a m ore tho ro u g h sea rch o f
m e m o ry for the targ et e ve n ts.
In a sim ilar v e in , R u b in an d B ad d e le y (1 9 89 ) co lle c ted re po rts of pe o ple ’ s
atten d a n ce at a se m in a r series a n d co m pa red re po rts to th e a tte n da n c e re co rd s
for the sem in a rs. A g a in forw a rd tele sco p ing w a s ob se rv ed . A no th er ty p e o f
v erifia b le e v ide n ce o f fo rw ard te le sco pin g w as co lle c ted b y T ho m pso n et a l.
(19 8 8 ) w h o ask e d p eo p le to ke e p d ia ries. A t a la ter tim e w h e n p eo p le rep o rte d
the d a te s o f the ev e nts fro m m em ory , th e d ia rie s w ere c o nsu lted to a sc e rta in th e
ac tua l d ates of th ose e ve n ts. T h o m p so n et a l. also o bse rv ed fo rw a rd te lesc o pin g
o f e v en t da tes.
H utten lo ch e r e t al. (19 8 8 ) p rov id ed a n e x pla na tio n o f fo rw ard te le sc o pin g
b ase d on tw o fac to rs. T h e first w a s inc re asin g in ac c u rac y of in form ation in
m e m o ry w ith e la pse d tim e . B a dd e ley , L ew is, a n d N im m o -Sm ith (1 97 8 ) ha d
p re v io u sly d em o nstrate d tha t the a c cu rac y o f p eo p le’ s m e m o ry (ab so lu te e rro r)
for w h e n e v en ts o cc u rre d d ec rea se d w ith ela pse d tim e . T h e sec o nd w a s
refe ren c e p e rio d b o un d ar ie s. In the H u tte n lo c he r e t a l. m o d e l, info rm ation a bo u t
o ld e r e v en ts is less p rec ise th an in fo rm a tio n ab o u t m o re re c en t e v en ts. T h us,
the re is a gre a te r p rob a b ility th a t o ld e r e ve n ts w ill b e te lesc o p ed . B e c au se e ve n ts
tha t o c cu rred o u tsid e th e e arly bo u n d ary of th e refe ren c e p e rio d (th o se th at ca n
b e forw a rd te le sc op e d in to it) a re o ld e r th an ev e n ts insid e th e e a rly bo u n da ry
(th o se tha t c an b e ba ck w a rd telesc o p ed ou t o f it) th e re su lt is n e t fo rw a rd
telesc o p in g o v er an y refe re nc e p eriod . N et fo rw ard te le sc op in g w ill inc rea se
o ve r p e rio d s in w h ich th e m o st re ce n t b o un d ar y is the pre sen t (b e ca u se th e re ca n
458
PROHASKA, BROWN, BELLI
ne v er b e b ac kw ard te le sco pin g o f fu ture e v en ts). R u b in an d B a d de ley (1 9 8 9 )
pro v id ed a sim ila r e xp la na tio n . In b oth th e H u tte n lo c he r e t a l. a n d R u bin a n d
B a d d ele y m od e ls, n et fo rw ar d telesc o p ing is a lw ay s g o in g to o cc u r, de sp ite th e
fa c t t h a t s o m e d e g r e e o f b a c k w a rd te l e sc o p i n g a l so o c c u rs . B a c k w a r d
te lesc o p in g is a w e ak e r effe ct tha n forw a rd te le sc o pin g b ec au se of th e g re a te r
im pre c isio n in d a tin g o ld er e v en ts th a n m o re re ce n t e v en ts, w h ich lea d s to a
gre a te r te nd e n cy to fo rw ar d tele sco p e o lde r e v en ts in to the re fere n ce pe riod tha n
to b a ck w ard telesc o p e m ore rec e nt e ve n ts o u tsid e of th e re fe re nc e pe rio d .
W h y is fo rw ard te lesc o pin g a pro b lem ? O n a p ra ctica l le ve l, th e p re sen c e o f
fo rw ar d te le sco pin g c a lls into q ue stio n the a cc u ra c y of the su rve y d ata o n w hic h
m a n y d e cisio ns a b o ut re sou rc e a llo c a tio ns a re m a d e. P ub lic p erc e ptio ns a n d
go v er nm en ta l p o lic y m ay b e b ase d on inflate d d a ta be c au se of forw a rd
te le sc o p in g e rro rs . O n a th e o r eti ca l le v e l o f m o re c o n c e rn to m e m o ry
re se a rc h ers, th e p re sen c e o f forw a rd tele sc op in g e rrors ra ise s q ue stio n s a bo u t
th e rep re sen tatio n o f te m p o ra l in form atio n in m em or y an d the p roc e sse s tha t
pe o ple u se to re c on stru ct te m p o ra l in form atio n.
O u r sta rtin g p rem ise is th at w h e n a ske d a n y tem p ora l q u estio n ab o u t
au to bio g ra p h ica l m em o ry, pe o p le e ng a ge in re c on stru ction to form an an sw e r
(F ried m a n, 1 9 9 3; T h o m p so n , S k ow ro nsk i, L arse n , & B e tz , 1 9 9 6). H o w ev e r, th e
re p re sen tatio n of the te m p o ral in fo rm atio n o n w h ich re co n stru c tion is ba se d is
hie ra rc h ic ally org a nise d (H u tte n lo c he r et a l., 1 98 8 ). W e m a inta in tha t th e
sp e c i fic q u e s tio n a sk e d w ill b e a n im p o rt a n t fa c t o r in t h e a m o u n t o f
re c o nstru ctio n in w h ich resp o nd en ts e n ga g e, be c au se p e op le on ly re co n struc t
to a lev e l o f d eta il su ffic ien t to form a n ap p rop ria te resp o n se . T h us, w h en p e o ple
are a sk ed : ``H a v e y ou be e n tre ate d b y a m e d ic al do c to r in th e la st six m o n th s? ’ ’
th e y re trie ve ch a rac te ristic s of th e ev e nt an d m a tc h th em ag ain st ch a ra c te ristic s
of th e re fere nc e p e rio d . F o r e xa m p le , p eo p le m ig h t c o nsid er h o w co ld it w as o n
th e ir la st d o c to r visit, o r w h a t the y w e re w ea ring , o r w h e th e r it w as d urin g a n
ac ad e m ic se m e ster. If th e se ch a rac teristic s m atc h th e re fe ren c e pe riod (c o ld ov e r
th e la st six m o n ths, be in g in sch o o l, etc .), th e y c an resp o n d ``Y es’ ’ an d sto p
re c o nstru ctin g at th at po in t. T he re is n o n ee d to rec o nstru ct a n e x ac t c alen d a r
da te . In c on tra st, a q u estio n suc h a s: ``O n w ha t d ate w e re yo u la st tre a te d b y a
m e d ic a l d oc tor? ’ ’ c o m p e ls resp o n d en ts to th ink ca refu lly ab o u t w h en th e ta rge t
ev e nt h a p pe n e d an d re co n stru c t an e x ac t d ate . W h en fa ce d w ith th e d ate
qu e stio n , resp o n d en ts m a y b e m o re lik e ly to e x ec u te a m ore ex ten siv e re trie va l
attem p t to estim a te th e d a te. T h u s, m o re co n tex tu al info rm a tio n a ssoc iate d w ith
re m e m b ering the la st e v en t is lik e ly to co m e to m in d . W e be lie v e th at w h e n
pe o ple spe n d le ss effo rt in re c o nstru ctin g th e tem p ora l in fo rm ation ab o ut ev e nts,
th e y w ill b e m o re in a cc u rate in th e ir re p or ts an d , th u s, th ey w ill ha v e a g re a te r
te n d en c y to fo rw ard te lesc o p e tho se re p or ts, c o nsiste nt w ith th e b o u nd a ry m od e l
of te le sco p in g first a d va n c ed by H u tte n lo c h er e t a l.
O n e stu dy b y L o ftu s, K lin g e r, S m ith , a n d F ie d le r (1 99 0 ), sou g h t to red u c e th e
am o un t o f o bse rv ed fo rw ard tele sco p ing in p eo p le’ s re p orts. In a n e xte nsio n o f
FORWARD TELESCOPING AND QUESTION FORMAT
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N ete r a n d W a k sb erg ’ s (1 9 6 4) p roc e d ure , th ey fou n d th at forw a rd tele sc op in g o f
rep o rts o f h ea lth p roc e du re s ov e r a tw o-m o nth refe ren c e p e rio d w ere re d u ce d
w he n p artic ip a nts w e re first a sk ed a b ou t th e sam e he a lth p ro ce d ure s o v er a six m o n th refe ren ce pe riod . W e su g g es t th a t th e ir pro c e du re m a y h a ve e n co u ra ge d
p eo p le w h o rec e iv e d th e six-m o nth p erio d first to e n g ag e in a m ore e xte nsiv e
retrie v al o f info rm ation in th e tw o -m o n th pe rio d in co m pa riso n to tho se w h o
o nly a nsw ere d for th e tw o -m o n th p eriod . A n sw erin g ab o u t th e six -m o nth p e rio d
first m ay ha v e ind ica ted to re sp o nd e nts th e im p o rta n ce of p re cise ly estim a tin g
for th e tw o -m o n th pe rio d , le a din g to a m ore c om p le te re c on stru ction to
d eterm ine w h e th e r a n e v en t h a d ind e e d o cc u rre d w ithin th e p ast tw o m o n ths. It
sh ou ld b e re m em b ere d, h o w e v e r, th at fo rw ard te le sc op in g is still q uite lik e ly to
o cc u r, as p rior inv e stig a to rs h av e de m o n stra te d, ev e n w h e n p eo p le e n ga g e in
ex ten siv e rec o nstru c tio n, b u t o ur hy p o th e sis is th at it w ill o c cu r les s o fte n tha n
w he n p eo p le’ s resp o n ses c an b e b a sed o n le ss e xte nsiv e re trie va l.
T o te st o ur h y po th esis w e c o nd u c ted tw o e xp e rim en ts. T h e m ajo r differe nc e
b etw ee n the m is th at E x pe rim en t 1 a ske d ab o u t an e ve n t (a v isit to a m ed ica l
d oc tor) fo r w hic h th e tru e da tes c o uld n o t b e v erifie d . H o w ev e r, E xp e rim en t 2
ask e d a b o ut e ve n ts (stu de n ts’ p a rtic ip a tio n in rese a rc h stu d ies) for w h ich the tru e
d ates co u ld be v e rified . O th e r diffe ren ce s b e tw e e n th e ex p er im en ts a re d iscu sse d
later.
EXPERIMENT 1
In E xp e rim en t 1, w e e x plo red forw a rd tele sco p ing u sin g a m e th o d o lo g y
co m m o n to su rve y re sea rc h. P a rtic ip a nts w e re ask e d e ith er a ``Y e s/N o’ ’ o r ex ac t
d ate q u estio n a bo u t b e in g tre ate d b y a m ed ic al d o c tor. T w o d iffe re n t re fere n ce
p eriod s, tw o m o n ths an d fo u r m o n th s w ere u sed . O u r p re d ic tion w a s th at le ss
telesc o p in g w ou ld b e o b serv e d w h e n p a rtic ip a n ts re co n stru c te d a n e x ac t d a te a s
a re sp on se .
Method
P a rtic ipa n ts.
P a rtic ip a nts w e re 20 5 u n de rg rad u ate stu de n ts at th e U n iv ersity o f A lb erta , w ho w ere e n rolle d in In trod u c to ry P sy c h olo g y d u rin g th e
sp rin g 19 9 5 sem este r.
P ro c e d u re .
D u rin g c la ss o n 3 1 M a rc h , 1 9 9 5 , e a c h p a rtic ip a n t w a s
ran d o m ly g ive n a fo ld ed a n d stap led she e t o f p ap e r. E a ch she et co n ta in ed on e
o f th re e qu e stio n s a bo u t visits to m e d ic al d o c to rs. T h e 2-M o n th g ro up ’ s qu e stio n
w as: ``In the last T W O m o nth s h a ve y o u b ee n tre ate d o r ex a m in ed b y a
p hy sicia n ?’ ’ T h e 4 -M o n th g ro u p’ s q ue stio n w a s th e sam e bu t w ith ``F O U R
m o n th s’ ’ rep lac in g ``T W O m o n th s’ ’ . T h e D ate g ro u p ’ s qu e stio n w a s: ``O n w ha t
d ate w e re y ou last ex a m in ed by a p h ysic ian . P lea se b e a s ex a ct as p o ssib le , b u t
estim a te th e d a y (or th e m o n th) if n ec essa ry ’ ’ . B ec a us e pa rtic ipa n ts w ere te ste d
460
PROHASKA, BROWN, BELLI
o n th e las t d a y of M a rc h , w e w e re ab le to u se p a rtia l re sp o n ses a n d
ap p ro xim a tion s, su ch a s ``F e b ru a ry’ ’ or ``Ja n ua ry 1 5 o r 1 6’ ’ . T o ke e p th e to ta l
nu m b er o f re fere n ce a n d d ate g ro u p s sim ilar th e re w e re tw ic e as m a n y sh ee ts
w ith th e da te q u estio n.
Results
T h e p erc en tag e s o f ``Y e s’ ’ re sp on se s in th e 2 - an d 4 -M o nth g ro u p s a n d th e
pe rc en tag e s o f d a te s th at fe ll w ith in ea c h refe ren c e p eriod are p res en ted in T a ble
1. A ch i-sq ua re a na ly sis rev e ale d th at th e 2 -M o nth g ro up g av e m o re ``Y e s’ ’
re sp o n ses (57 % ) th an the D a te g rou p ga v e rep o rts th at fe ll w ith in th e tw o -m o n th
2
re fe ren c e p erio d (3 5 % ), c
(1, N = 15 5 ) = 7 .4 5 , P < .0 1 . H ow e v er, th e d iffe ren c e
2
be tw e e n th e 4-M o n th (6 2 % ) a n d D a te (49 % ) w as n o t sig n ific an t, c
(1 ,
N = 15 0 ) = 2 .2 6 .
It is in tere stin g to n ote tha t th e pe rce n tag e o f p eo p le w h o a n sw e re d ``Y e s’ ’
did n o t c ha n g e w ith th e ch a ng e in th e le n g th of th e re fe re n ce p erio d . T h at is,
57 % a nsw e red ``Y es’ ’ in th e tw o -m o nth ref ere nc e pe riod a nd 6 2 % a n sw ere d
``Y e s’ ’ in th e fou r-m o n th re fere n ce pe riod , a n in c re a se o f o nly 5% d esp ite a
50 % inc rea se in th e re fere n ce p erio d. In co n tra st, in th e D ate g ro u p th e
pe rc en tag e of p a rtic ip a nts w h o re p orte d b e in g tre a te d rose from 3 5% d urin g th e
la st tw o m o n ths to 49 % du rin g th e las t fo u r m o nth s, a n in cre as e o f 14 % .
Discussion
O u r h y p oth esis, th a t th e d a te q u estio n w o u ld re su lt in le ss forw a rd te le sc op in g
th a n the y e s/n o qu e stio n , w as sup p o rte d in th e tw o -m o n th refe ren c e p eriod .
T h e re are sev e ral p o ssible re aso n s w h y the sa m e p a tter n o f re su lts w as n o t
ob se rv ed in th e fo u r-m o n th refe re n ce pe rio d . O ne re aso n m ay be d u e to the u se
of stud e nts a s p artic ip a nts. T he en d of th e fo u r-m o n th pe riod co in cid ed w ith th e
en d o f th e p rio r se m e ster, th us p ro v idin g a firm bo u n d ary th at m a y h av e
a tte n u a te d th e 4 -M on th g ro u p ’ s ten d e n c y to fo rw a rd te le sc o p e . A n o th e r
po ssib ility, c o nsisten t w ith ou r h y p o th e sis, is tha t th e D a te g ro u p ’ s m o re
TABLE 1
Experiment 1
R e fe r e n c e P e r io d
C o n d itio n
2 - M o n th , n = 5 4
T w o m o n th s
5 7%
4 - M o n th , n = 5 0
D a te , n = 1 0 1
F o u r m o nths
6 2%
3 5%
4 9%
P e rc e n t a g e o f p a rti ci p a n ts in d ic a tin g th e y h a d b ee n e x a m in e d
b y a m e d i ca l d o c to r w i th in t h e re s p e c ti v e re fe re n c e p e ri o d .
FORWARD TELESCOPING AND QUESTION FORMAT
461
ex ten siv e retriev a l led to th e ir rem em b erin g m ore e v en ts in th e lo ng e r re fere n ce
p eriod . F in ally, a th ird p o ssibility , also c o nsiste nt w ith o ur hy p o th e sis, is th a t th e
tw o - an d fou r-m o n th re fere nc e p e riod s w ere n o t su fficien tly d iffe re nt to a llo w
p artic ipa n ts to d istin g u ish th e fa m ilia rity o r a va ila b ility o f th e ev e n t. T h at is,
p artic ipa n ts m a y h av e sim p ly ju d g e d w h e th e r a m e d ic a l tre atm en t w as re c en t
an d thu s w ith in ra n g e (w h eth er th e ra n ge w as tw o - o r fou r-m on th s), o r n o t re c en t
an d thu s o u t o f ran g e.
Inte rp re tatio n s of E x p e rim en t 1 su ffe r fro m all o f th e p rob le m s inh e ren t in
d ata tha t c an n o t b e v erifie d th at w e re d isc u sse d ea rlie r. F o r ex am p le, the re c ou ld
h av e b ee n d iffe ren ce s in d o cto r v isits b e tw e en th e g ro u p s o f w h ic h w e h ad n o
k no w led g e . B ec au se w e d id n o t h a ve ac c e ss to pa rtic ipa n ts’ a c tu a l m ed ica l
rec o rd s, n o a tte m p t c o uld b e m ad e to c ollec t d ire c t e vid en c e o f d iffe ren tial
telesc o p in g b etw ee n the refe ren c e p e rio d s. E x pe rim en t 2 w as d e sig n ed to
circ um v en t th is lim ita tio n .
EXPERIMENT 2
In E x p erim e n t 2 , th e e ve n ts w e u sed w e re stu d en ts’ pa rtic ip ation in rese arc h
stud ies du rin g an a c ad em ic sem este r. P a rtic ip a n ts re p o rte d eithe r th e nu m b er o f
tim es th e y ha d p a rtic ip a te d in rese arc h stu die s (the y c ou ld h av e p a rtic ip a te d
o nc e , tw ic e, o r n o t a t all) o r th e ex a ct da tes o n w hic h th ey ha d p a rtic ip a ted . T h e
d ata w ere c o llec te d th re e m o n th s after th e se m e ster b e g an an d a tw o-m on th
refe ren c e pe rio d w a s u sed so th at fo rw a rd telesc o p in g e rrors w o u ld b e p ossib le.
A s w e w e re ab le to a sce rtain w he n stu de n ts p artic ipa te d fro m atte n d an c e she e ts,
w e w e re a b le to v erify p a rtic ip a n t’ s re po rts.
Method
P a rtic ipa n ts.
P a rtic ip a nts w e re 1 43 un d erg ra du a te stu d en ts a t L e h m a n
C olleg e , T h e C ity U n iv e rsity o f N e w Y o rk , w h o w e re e nro lled in tw o sec tio n s o f
G en e ra l P sy c ho lo g y d urin g th e a u tu m n 1 99 5 se m e ste r. T his co u rse co n tain s a
rese arc h req u irem en t a n d on e o f the w a y s tha t stud e n ts ca n (an d m o st o ften d o )
fulfil th is re q uire m e nt is to p artic ip ate in tw o re sea rch stud ie s.
P ro ce d u re .
R e se a rc h stu d ie s w e r e a v a ilab le fo r stu d en t p a rtici pa tio n
thro u gh o u t th e sem este r, fro m 1 1 S ep te m b er to 12 D ec em b er, o n v ario us d ate s
an d tim e s, a n d stud e n ts se lec te d th e stu d ie s, d ate s, an d tim e s th e y p re fe rred . A t
the e nd of th e ir c lasse s, o n 6 D e ce m be r, e x ac tly th re e ca le n da r m on th s a fte r
cla sses b eg an , stu d en ts w e re g iv en o n e o f tw o q ue stio n s a b ou t th eir p a rtic ip a tio n
in re sea rch stu die s. T he form at w a s th e sam e a s in E xp e rim en t 1; e ac h
p artic ipa n t w a s g iv e n a fo ld ed sh ee t o n w hic h o n e o f th e tw o p o ssible qu e stio n s
w as p rin te d. T h e R e fe ren c e P e riod g ro u p w e re sim p ly ask ed to in d ic ate th e
n um b er o f stud ies in w h ic h the y p a rtic ip a te d d u ring th e last tw o m o nth s. T h e
D ate g ro u p w as ask e d for th e ex a ct d ate (s) o n w h ich th e y pa rtic ipa ted . B e c au se
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PROHASKA, BROWN, BELLI
w e w ere in te rested in forw a rd te le sco p in g, w e a rra n ge d tha t m a ny stu die s w e re
av a ila b le fo r pa rtic ip ation in S e p te m b e r (i.e. e arlie r th an th e re fe re n ce p e rio d )
an d tha t th e tw o in stru c tors re m in d ed stu d en ts ab o u t th is req u ire m e n t thro u gh o u t
th e ea rly p a rt o f th e se m e ster.
Results
F irst, w e co m pa red the p e rce n tag e o f ``Y es’ ’ re sp o nse s by th e R efe ren c e P e rio d
gro u p to th e pe rce n tag e o f d ate s re po rte d b y th e D a te g rou p th a t fe ll into th e
tw o -m on th refe ren c e p eriod . T he se d a ta a re pre sen te d in T a ble 2 . A c hi-sq ua re
2
an aly sis fo u n d n o s ig n ifica n t d iffe re n c e b e tw e e n th e g ro u p s, c
(2 ,
N = 14 3 ) = 2 .6 . H o w e v e r, e v id e nc e o f fo rw a rd tele sco p ing w a s o b se rv e d w ith in
th e R e fere n ce P e rio d g ro u p . S p ec ific ally , a lth o ug h th e D ate g ro u p w as e v en ly
div id e d b etw ee n tho se w ho rep o rte d o n e (4 0% ) a nd th ose w h o re po rte d tw o
(4 % ) d a te s, in th e R e fe ren c e Pe riod gro u p m o re p articip a nts (5 3 % ) re p or te d
2
co m ple tin g tw o stu d ie s th an rep o rte d co m ple tin g o n ly o n e (2 9% ), c
(2 ,
N = 83 ) = 1 6 .3 , P < .0 0 5 .
T h ese d a ta a lso a llo w ed u s to e x am in e d iffere nc e s in th e a cc u rac y o f rep o rts
be tw e e n th e tw o gro u ps b y m a tch ing p artic ip an ts’ re po rts to a tte nd a n c e sh e ets.
F o r th e R e fe re n ce P erio d g ro u p, c orre ct resp o n se s w o u ld be ``Y e s’ ’ resp o n ses a n d
re c o rde d p artic ipa tion w ithin the tw o -m o nth re fe re nc e p eriod . S im ilarly, fo r th e
D a te c on d itio n, th e rep o rte d d a te sim ply h a d to be c o rre c t a s to w he th er it w a s
w ith in o r ou tsid e the tw o-m on th refe ren c e p e rio d . T h ese d ata a re pre sen ted in
T a ble 3 . T h e R e fere n ce Pe rio d g rou p w as sig nifica n tly m o re like ly to b e in c orre c t,
2
eithe r w h e n re p ortin g tha t th ey h ad p articip ate d tw ic e , c (1 , N = 68 ) = 4 .4 , P < .0 5 ,
2
or on c e, c
(1, N = 4 8) = 4.2 , P < .0 5 . S p e cifica lly , 8 2% o f the p a rtic ip a te s w h o
said the y h ad p artic ip a te d in tw o stud ies du rin g th e tw o -m o n th re fe re n ce p erio d
w e re in co rrec t. In c on trast o n ly 5 8 % o f tho se w h o g a ve tw o d a tes w ith in the tw o m o n th re fere n ce p e rio d w e re in c orre ct. S im ila rly 58 % o f tho se w h o said th ey h a d
pa rtic ip ated o nc e d u rin g th e tw o -m o nth re fe re n ce pe rio d w ere in co rre ct, w hile
on ly 2 9 % of th o se w h o ga v e o ne d a te w ithin th e tw o -m o n th refe ren c e p eriod w e re
in c o rre c t. T h e m o st co m m o n erro r w as fo rw ard tele sco p ing ; tha t is, stu de n ts said
TABLE 2
Experiment 2
R e s p o n se
C o n d it io n
T w ic e
O nce
N o ne
R e fe re n ce P e ri o d , n = 8 3
5 3%
2 9%
18%
D a te , n = 6 0
4 0%
4 0%
20%
P e rc e n ta g e o f p a rt ic ip a n ts in d i ca t in g th ey h a d p a rtic i p a te d in re se a rc h
s tu d i e s w it h i n th e tw o -m o n th r ef ere n c e p e rio d .
FORWARD TELESCOPING AND QUESTION FORMAT
463
TABLE 3
Experiment 2: Accuracy by Condition and Responses
R e fer en c e P e rio d Ð s a id T W O
C o r re c t
In c o r r e c t
8 (1 8 % )
3 6 (8 2 % )
D a t eÐ 2 d a te s i n p e rio d
1 0 (4 2 % )
1 4 (5 8 % )
R e fer en c e P e rio d Ð s a id O N E
1 0 (4 2 % )
1 4 (5 8 % )
D a t eÐ 2 d a te s : 1 i n , 1 o u t o r 1 d a t e i n
1 7 (7 1 % )
7 (2 9 % )
the y h ad pa rtic ip a ted w ithin th e tw o -m o n th pe riod (in O c to b e r or N o v e m b e r),
w he n ac tua lly th ey h ad p artic ip ate d e a rlie r (in Se p te m b er).
Discussion
Inc rea se d forw a rd te le sc op in g b a se d o n a c o m p a riso n o f re p or te d an d ac tua l
info rm a tio n b y th e g rou p a ske d th e ea sie r q ue stio n w as o b serv e d. Ind irec t
ev id en c e o f fo rw a rd te lesc o p in g w as o b se rve d w ith in th e R e fere n ce P erio d
g ro u p (i.e . m ore ``T W O ’ ’ re sp on se s), bu t n ot b e tw e en th e gro u p s (i.e. th ere w ere
n ot m o re ``Y e s’ ’ re sp o n ses from the R efe ren ce P e rio d g ro u p th a n da tes w ithin
the re fe re n ce p erio d by th e D ate g ro u p ). W e th ink th is lac k o f a b etw ee n -gro u p s
d iffe re n ce is d u e to the fa ct th at the re w as a h igh le ve l o f pa rtic ip a tio n in th e
ev e n t in q u e stio n . U n lik e th e e ve n t u tilise d in E xp e rim en t 1 , v isitin g a d o cto r fo r
a rou tine c h ec k -up , p articip ation in a re se arc h stud y w a s, in a se n se, a c ou rse
req u ire m en t, so ou r rate of p o sitive re spo n ses fro m b o th g ro up s w as h ig h.
GENERAL DISCUSSION
O ur sta rtin g pre m ise , tha t p eo p le u se rec on stru ction w h e n a n sw erin g qu e stio n s
ab o u t th e tim e o f a u to b io gra ph ica l e ve n ts, is a w id e ly a cc e p te d o ne . In d ee d , th is
p re m ise is a cc ep ted in reg a rd to the d atin g o f p ub lic ev e nt s as w e ll (e .g . B ro w n,
1 9 9 0 ; B u rt & K e m p , 1 9 9 1 ). F u rth e rm o re , th e p re m i se th at m e m o ry is
h ie rarc h ic a lly o rga n ise d also is w ell ac c ep ted (e .g . B a rsa lou , 1 98 8 ; B e lli, th is
issu e; B ro w n , 1 9 9 0; C on w a y , 1 9 9 6; H u tte n loc h er e t a l., 1 9 8 8 ). F ina lly ,
B ad d ele y e t a l. (1 9 7 8), H u tte n lo c h er et al. (1 9 88 ), a nd R ub in a n d B ad d ele y
(19 8 9 ) d em o nstra ted th at fo rw ard te le sc op in g is rela te d to the in cre asin g
ina cc u ra cy of m em o ry w ith e la p sed tim e .
O ur sp e cific h y p oth e sis, b ase d o n th e se th ree starting p re m ises, w a s th a t th e
q ue stio n fo rm at w ou ld in flu e n ce th e am o un t of forw a rd te le sc op in g o b serv e d in
p eo p le ’ s rep o rts. W e b e lie ve tha t th e m ore diffic u lt q ue stion (``R e po rt th e ex ac t
d ate’ ’ ) le d re spo n d en ts to e n ga g e in a m o re tho ro u gh re c o nstru ctiv e pro ce ss,
resu ltin g in a b e tte r lo c ation of th e e v en ts in tim e a n d g rea te r rela tiv e ac c ura cy .
T h e sim ple r q u estion s (``W ere yo u tre ate d? ’ ’ ``H o w m an y tim e s did yo u
464
PROHASKA, BROWN, BELLI
pa rtic ip ate? ’ ’ ) led re spo n d en ts to sim p ly in fer th e e ve n ts’ re c en cy , ra th e r tha n
attem p t to pre cise ly lo ca te e ac h in tim e.
T h e fo cu s o f th e p re sen t stu d y w a s on a uto b io g rap h ica l e v en ts w ith re lative ly
lo w fre q u en c ie s of o cc u rre n c e. A sk ing th e m o re difficu lt q u estio n a bo u t h igh e rfre q u en c y e v en ts (e .g . ``R ep o rt th e e x ac t da tes d u rin g th e la st tw o m o nth s tha t
yo u : p u rc h a sed g a so lin e for yo u r c ar; ate be e f fo r d in n e r; ex er cised ’ ’ ) m ig h t
pro d uc e to o h ig h a d em a nd o n p e op le an d lea d to less ac cu ra te re su lts. In d e ed ,
M e a n s an d L o ftus (1 9 9 1) sho w e d tha t p e op le’ s stra teg ies for an sw erin g
qu e stio n s c h an g e d de p en d ing on th e freq u en c y o f the e v en ts. H ow e v er, the ir
stu d y also d em o nstrate d th a t th e m a nn e r in w h ich p eo p le a re q u e stio ne d co u ld
in c re a se a cc u rac y e v en w ith h ig h-freq u e n cy ev e nts. F ina lly, fo rw ard te le sc op in g
also is ob se rve d w h e n p e op le a re ask e d to rep o rt tem p or al in form a tio n a bo u t
disc rete p u b lic e ve n ts a n d w e b e lie ve it lik ely th a t resu lts sim ilar to tho se o f th e
pre se nt stud y w o uld b e o b serv e d in th is do m ain as w e ll.
A s the m o d e ls o f H u tten loc h er e t a l. (1 9 8 8) a nd R ub in an d B a dd e ley (1 9 8 9 )
in d ic a te, so m e fo rw a rd te le sc o pin g is a lm o st a lw a ys go in g to o c cu r in p e o ple ’ s
re p o rts, a n d w ill co n tin u e to b e a pro b lem fo r surv ey rese a rch e rs w h en e v er the y
ca n no t v e rify re sp o nd e n ts’ rep o rts. M o reo v er , th ere a re situ a tio n s fo r w h ich th e
da tin g q ue stio n m ig ht n ot n e ce ssa rily le a d to m o re a c cu rate re sp on se s. F o r
ex a m p le, a skin g p eo p le to d a te fre qu e n tly o cc u rrin g m un d a ne e v en ts m igh t lea d
to un d e r-re po rting be c au se th e relev a n t ev e n t in sta nc e s a re ra p id ly fo rg otten .
N o n e the less, o u r da ta su gg e st th at ask in g resp o n d en ts to pro v id e a m o re p re cise
re sp o n se reg a rdin g th e tim ing o f e v en ts w ill e n co u rag e a m o re th o ro u g h
re c o nstru ctio n w h ic h w ill re d u ce forw a rd te le sco p in g. T h u s, b y m ak in g p e o ple
w o rk a little h ard e r in d e term in ing w h e n ev en ts h a d oc c urre d , su rv ey re sea rch e rs
w ill lik ely ga in m o re a cc u ra te d a ta .
REFERENCES
B a c h m a n , J .G ., & O ’ M a lle y , P .M . (1 9 8 1 ). W h e n fo u r m o n th s eq u al a y e ar: In c o n s i st e n c ie s in
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B a d d e le y , A .D ., L e w is , V ., & N im m o -S m i th , I. (1 9 7 8 ). W h e n d i d y o u l a st . . .? In M .M . G ru n e b e rg ,
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B a rs al o u , L .W . ( 1 9 8 8 ). T h e c o n t en t a n d o rg a n i za t io n o f a u t o b io g r ap h ic a l m e m o ries . In U . N e is s e r
& E . W in o g ra d (E d s .), R e m e m b e r in g r e c o n s id er e d . N e w Y o rk : C am b rid g e U n iv er si ty P r es s .
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P o t e n t ia l im p ro v e m e n ts in th e q u a li ty o f re tro s p e c tiv e re p o rts in s u rv e y s . M e m o r y , 6 .
B ro w n , N .R . (1 9 9 0 ). O rg a n i z at io n o f p u b l ic e v e n ts in lo n g -t e rm m e m o r y . J o u r n a l o f E x p er i m e n ta l
P s y ch o lo g y : G en e r a l, 1 1 9 , 2 9 7 ±3 1 4 .
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