2013. Vol.4, No.12, 1014-1017
Published Online December 2013 in SciRes (http://www.scirp.org/journal/psych) http://dx.doi.org/10.4236/psych.2013.412147
Double-Step Adaptation of Saccadic Eye Movements Is
Influenced by Priming with Age Stereotypies
Otmar Bock1, Valentina Grigorova2, Milena Ilieva2
1Institute of Physiology and Anatomy, German Sport University, Köln, Germany
2Institute of Neurobiology, Bulgarian Academy of Sciences, Sofia, Bulgaria
Received August 13th, 2013; revised September 16th, 2013; accepted October 12th, 2013
Copyright © 2013 Otmar Bock et al. This is an open access article distributed under the Creative Commons At-
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Age related deficits of sensorimotor adaptation have been observed earlier with arm, but not with eye
movements. Here we evaluate whether deficits of eye adaptation may depend on the subjects’ believes
about their own sensorimotor abilities. To find out, elderly subjects were primed with positive or negative
age stereotypes using the scrambled-sentence task, and were then exposed to a double-step saccade adap-
tation task. The outcome was compared to data from an earlier study with unprimed elderly persons. We
found adaptation to be stronger after positive priming than after negative or no priming, with no differ-
ence between the latter two. Aftereffects of adaptation were not modified by priming. From this we con-
clude that positive primes enhanced workaround strategies, but not adaptive recalibration, while negative
primes failed completely, possibly because of a floor effect.
Keywords: Old Age; Plasticity; Strategies; Recalibration; Societal Stereotypies
The human sensorimotor system adapts readily to a wide
range of distortions (Bock, 2013): when the visual or the force
environment is systematically altered, our behavior is initially
perturbed but gradually normalizes with extended practice. This
ability deteriorates in old age; however, it has been shown that
the speed and magnitude of adaptive change are reduced, while
aftereffects remain intact (Bock, 2005; Fernández-Ruiz, Hall,
Vergara, & Díaz, 2000; McNay & Willingham, 1998). Since
aftereffects are thought to reflect adaptive recalibration only,
unbiased by strategies (McNay & Willingham, 1998; Redding
& Wallace, 1996), the above work indicates that strategic con-
trol but not adaptive recalibration is degraded in old age. Accor-
dingly, age-related deficits of adaptive change were found to be
associated with cognitive decline (Bock & Girgenrath, 2006).
The above studies dealt with the effects of old age on the
adaptation of arm movements. We have recently expanded this
work to oculomotor saccades and found no age-related deficits
for saccadic adaptation under single-task conditions, nor under
dual-task conditions when the second task was spatially adja-
cent; an adaptation deficit only emerged when the second task
was located further away (Bock et al., under review). We at-
tributed that deficit to the well-known shrinkage of the attention
focus in old age (Ball & Owsley, 1993; Beurskens & Bock,
2012; Sekuler & Ball, 1986), and concluded that saccadic ad-
aptation per se is largely age-independent.
It seems surprising that saccadic adaptation should be im-
mune to age-related decay, while other characteristics of ocular
saccades deteriorate: their speed and accuracy decreases (Bono
et al., 1996; Paquette & Fung, 2011), and their path across a
visual scene becomes less efficient (Chapman & Hollands,
2006; Maltz & Shinar, 1999). In fact, elderly subjects in our
preceding study didn’t adapt as well as young ones (Bock et al.,
under review), only the deficit didn’t reach statistical signifi-
cance. With these arguments casting doubt on our earlier con-
clusion, we decided to scrutinize it with a fresh approach.
Following the arguments of others, we reasoned that sen-
sorimotor performance in old age is determined not only by
biological decay, but also by the actor’s confidence in her/his
own capacity. This has been shown by studies which manipu-
lated the self-confidence of seniors by priming them with so-
cietal preconceptions about the abilities of elderly persons:
positive age stereotypes (words such as “mature”) enhanced,
and negative ones (words such as “frail”) degraded seniors’
performance on tasks such as locomotion (Hausdorff, Levy, &
Wei, 1999), chair rising (Levy, 2000) and handwriting (Levy &
Leifheit-Limson, 2009). We hypothesized that saccadic adapta-
tion is affected by self-confidence as well, and therefore is im-
paired in elderly persons who assimilate negative societal
stereotypes towards old age, but not in those who assimilate
positive ones. This differential compliance with societal ste-
reotypes would increase intersubject variability, and thus might
have reduced the significance level for age differences in our
preceding adaptation study to below 0.05. To explore this view,
we now compare saccadic adaptation in elderly participants
primed with positive versus negative stereotypes of old age.
Sixteen healthy right-handed subjects participated. They
O. BOCK ET AL.
were 58.7 ± 4.4 year old, had normal or corrected- to- normal
vision, were native Bulgarian speakers with different education
levels, and were naïve to the purposes of the experiment. All
signed an informed consent to this study, which was pre-ap-
proved by the Ethics Committee of the Institute of Neurobiol-
ogy at the Bulgarian Academy of Sciences in Sofia.
Subjects were first primed with age stereotypes using an es-
tablished procedure, the scrambled sentence task (Bargh, Chen,
& Burrows, 1996). Each person was given 20 lists of five
words, and had to select four words from each list to formulate
a meaningful sentence; the fifth, non-fitting word had to be
crossed out. Unbeknown to the subjects, one of the four se-
lected words was either a positive or a negative age stereotype
(e.g., “wisdom” versus “decay”). Eight subjects received lists
with positive stereotypes, and the other eight with negative ones;
all were instructed to proceed at their own pace. The prime
words came from a pilot study in which eight persons, aged 50
to 65, rated a list of 15 experimenter-selected words on two
ten-point Likert scales, one scale for “maturity” and the other
for “frailty”. The 10 words with the highest “maturity” rating
(5.0 to 8.0) and the 10 with the highest “frailty” rating (6.3 to
8.3) were repeatedly used as primes for the main experiment.
The scrambled sentence task was followed by a saccade ad-
aptation task, using procedures established in our earlier work
(Bock, Schmitz, & Grigorova, 2008; Grigorova, Bock, & Bo-
risova, 2013). In single-step trials, a target of 7 mm diameter
was presented in the center of the screen for 750 - 1500 ms,
enclosed by a circle of 11 cm radius. The target then jumped
onto the circle in one of eight randomly selected directions (0,
45, 90, 315 deg, where 0 deg denotes rightwards, and 90 deg
upwards), and returned to the center 760 ms later. In dou-
ble-step trials, the target jumped onto the circle, shifted along
the circle by −15 deg (clockwise) after 200 ms , and returned to
the center 640 ms later. Twenty successive trials constituted an
episode, and were separated from the next episode by a short
rest break. The adaptation task consisted of a baseline phase
with two single-step episodes, followed by an adaptation phase
with 25 double-step episodes, and then by an aftereffect phase
with two single-step episodes.
The data of eight subjects from another study (Bock et al.,
under review) were used as non-priming control. Those sub-
jects participated in the saccade adaptation task but not in the
scrambled sentence task, were healthy, right-handed and 58.7 ±
4.4 years old.
Horizontal and vertical eye movements were registered by
electrooculography (DC-EOG) with a band pass filter of 0.08 -
100 Hz. Signals were digitized with a resolution of 0.01 deg/bit
and a sampling rate of 100 Hz, and calibration was repeated
every five episodes. Custom-designed interactive software de-
termined saccade direction as the angular difference between
first target step and primary saccade, in the plane of the screen.
The software also determined saccade latency as the delay be-
tween first target step and the onset of primary saccade. Sac-
cades with latencies beyond 270 ms were discarded, since they
may be influenced by reprogramming towards the second step
(Becker & Jürgens, 1979). Mean saccade directions for each
subject and episode were adjusted by subtracting the sub-
ject-specific baseline values before graphical presentation and
Figure 1 illustrates that during the adaptation phase, saccade
Saccade direction for each episode of the adaptation phase (25 episodes)
and the aftereffect phase (2 episodes). Means across subjects primed
with positive age stereotypes are shown in grey, those across subjects
primed with negative age stereotypes in black, and those across non-
primed control subjects are dashed. For better clarity, no error bars are
direction gradually increased towards the negative, as expected
for adequate adaptation. This increase was most pronounced in
the group primed with positive age stereotypes, reaching a
mean of −8.1 deg across the last five adaptation episodes. The
five-episode mean of saccade direction was only −4.7 deg in
the control group and −4.4 deg in the negatively primed group.
When a deviant, non-adapting subject was excluded (84% of
data from that subject were positive rather than negative), the
five-episode mean in the negatively primed group changed to
−5.6 deg. In fact, the deviant subject is excluded in Figure 1
and in the reported statistical analyses. The five-episode means
of saccade direction in all subjects were submitted to an
one-way analysis of variance (ANOVA) with the factor Group,
which yielded statistical significance (F(2,20) = 9.38; p =
0.0013). Fisher’s LSD post-hoc tests revealed significant dif-
ferences between positive and negative group (p < 0.01), be-
tween positive and control group (p < 0.001) but not between
negative and control group (p > 0.05).
Figure 1 further shows that saccade direction during the last
two (aftereffect) episodes was quite similar in all groups. Ac-
cordingly, when mean saccadic direction across both aftereffect
episodes was submitted to one-way ANOVA, no significance
was yielded (F(2,20) = 0.014; p > 0.05).
The present study manipulated subjects’ performance th-
rough semantic priming. This technique is thought to activate a
specific node in a lexical network and thus to facilitate the sub-
sequent processing of words with similar meaning (Kiesel,
Kunde, & Hoffmann, 2007). However, it also was found to
influence higher-order mental functions such as creativity
(Mayer & Mussweiler, 2011), self-confidence (Levy, Hausdorff,
Hencke, & Wei, 2000), product preference (Strahan, Spencer,
& Zanna, 2002) attention focus (Hüttermann, Memmert, &
Bock, 2012) and motivation (Hart & Albarracín, 2009; Radel,
Sarrazin, Legrain, & Gobancé, 2009). We used this approach to
activate positive or negative age stereotypes in our subjects, and
observe the consequences on saccadic adaptation.
Our data document a beneficial influence of positive primes
on performance during the adaptation phase, but not during the
aftereffect phase. This suggests, according to established rea-
Open Access 1015
O. BOCK ET AL.
soning (Bock, 2005; McNay & Willingham, 1998), that posi-
tive age stereotypes enhanced workaround strategies but not
adaptive recalibration. Somewhat surprisingly, negative primes
had no noticeable effect at all: they modified neither recalibra-
tion nor strategies. One possible explanation is that priming
with negative age stereotypes is less efficient than priming with
positive ones. Another explanation could be social: maybe sub-
jects came to the laboratory already with a negative attitude
towards old age, and negative priming was therefore precluded
by a floor effect. There indeed exists empirical evidence that in
Bulgaria, compared e.g. to Germany, old age is regarded less
favorably. Bulgarians rate the social status and the economical
contribution of elderly persons much lower than Germans do,
and rate their own experience of discrimination due to old age
as much higher than Germans do (Abrams, Vauclair, & Swift,
2011). These findings might be related to the fact that suicide
rates among the elderly are substantially higher in Bulgaria than
in Germany (Shah, Bhat, McKenzie, & Koen, 2007). To decide
between the two explanations, it would be desirable to compare
the effects of positive versus negative age priming in different
cultures, including those who traditionally venerate their elders.
In this respect, it is interesting to note (Levy & Langer, 1994)
that memory loss in old age is more severe among Americans
with intact hearing than in American Deaf (who don’t experi-
ence spoken age stereotypes), and also more severe than in
mainland Chinese with intact hearing (who live in a culture that
honors old age).
The outcome of our study is in accordance with the hypothe-
sis stated in the Introduction section. Thus, the strategic contri-
bution towards saccadic adaptation might deteriorate in some
seniors more than in others, depending on their assimilation of
societal stereotypes, and only reaches statistical significance
when the role of stereotypes is controlled for by priming. This
could explain why no reliable deficit was observed when un-
primed older subjects were compared to young ones (Bock et
al., under review), but a robust deficit emerged when older
negatively primed subjects were compared to older positively
primed ones in the present study. In any case, age-related dec-
rements of saccadic adaptation, like those of arm adaptation
(Bock, 2005; Fernández-Ruiz et al., 2000; McNay & Willing-
ham, 1998), seem to afflict strategies but not recalibration. The
decrements seem to be less pronounced for the eyes than for the
arm, where a significant difference between age groups was
repeatedly observed even without primes (Bock, 2005;
Fernández-Ruiz et al., 2000; McNay & Willingham, 1998),
possibly because of a stronger cortical involvement in the con-
trol of arm versus eye movements.
The present study takes its place alongside other researches
that documented the role of social preconceptions on sensori-
motor performance (Hausdorff et al., 1999; Levy, 2000; Levy
& Leifheit-Limson, 2009), and thus highlights the potential
dangers of a vicious circle where negative attitudes towards old
age may activate performance deficits in the elderly by way of
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