incentive effects on cardiovascular reactivity in active coping with unclear task difficulty

vier.com/locate/ijpsycho

International Journal of Psychophy

Incentive effects on cardiovascular reactivity in active coping

with unclear task difficulty

Michael Richter *, Guido H.E. Gendolla

FPSE, Department of Psychology, University of Geneva, 40 Bd. du Pont d’Arve, CH-1211 Geneva 4, Switzerland

Received 25 May 2005; received in revised form 7 September 2005; accepted 20 October 2005

Available online 28 November 2005

Abstract

Two experiments with a total of 96 participants assessed cardiovascular response in active coping. The studies were run in 2�2 designs and

manipulated the clarity of task difficulty (clear vs. unclear) and incentive value (low vs. high) of a memory task, which was either easy

(Experiment 1) or extremely difficult (Experiment 2). In accordance with the theoretical predictions of motivational intensity theory [Brehm, J.W.,

Self, E.A., 1989. The intensity of motivation. Annu. Rev. Psychol. 40, 109–131; Wright, R.A., 1996. Brehm’s theory of motivation as a model of

effort and cardiovascular response. In: Gollwitzer, P.M., Bargh, J.A. (Eds.), The Psychology of Action: Linking Cognition and Motivation to

Behaviour, Guilford, New York, pp. 424– 453], systolic reactivity varied directly with incentive value when task difficulty was unclear. In

contrast, when task difficulty was clear, incentives had no influence and cardiovascular reactivity was low. These findings provide the first

evidence for the predictions of motivational intensity theory with regard to unclear task difficulty and complete past research that has focused on

the effects of fixed and unfixed task difficulty on cardiovascular reactivity.

D 2005 Elsevier B.V. All rights reserved.

Keywords: Unclear task difficulty; Cardiovascular reactivity; Active coping

1. Introduction

Research in cardiovascular reactivity has provided ample

evidence for an integrative analysis of cardiovascular (CV)

response in active coping (Wright, 1996). The integrative

analysis builds on the predictions of motivational intensity

theory (Brehm and Self, 1989) about the mobilization of

resources (i.e. effort) in instrumental behavior and Obrist’s

active coping approach to cardiovascular adjustments (Obrist,

1976, 1981). Following Wright’s integrative analysis, research

has nearly exclusively focused on CV responses when task

difficulty is either fixed on a certain level (fixed difficulty) or

can be liberally chosen by the performer (unfixed difficulty)

(see Wright, 1998; Wright and Kirby, 2001). However,

motivational intensity theory makes also predictions for a third

type of task difficulty: unclear difficulty.

Numerous studies have provided compelling evidence that

CV reactivity is proportional to fixed and clear task difficulty

0167-8760/$ - see front matter D 2005 Elsevier B.V. All rights reserved.

doi:10.1016/j.ijpsycho.2005.10.003

* Corresponding author. Tel.: +41 22 379 92 32; fax: +41 22 379 92 29.

E-mail address: [email protected] (M. Richter).

as long as task success is possible and justified by success

importance (i.e. potential motivation) (Bongard, 1995; Bongard

and Hodapp, 1997; Gellatly and Meyer, 1992; Gendolla, 1998;

Gendolla and Krusken, 2001a, 2002a,b; Gerin et al., 1995;

Light, 1981; Lovallo et al., 1985; Sherwood et al., 1990; Smith

et al., 1990; Smith et al., 1997, 2000; Storey et al., 1996). In

this process, the importance of success determines the level of

potential motivation which is the amount of resources that is

maximally justified for goal attainment. If success is neither

possible nor justified, CV reactivity is low, because no

resources are invested in task performance. Research has

shown as well that resource investment is directly related to

success importance when task difficulty is not fixed on a

certain level (Fowles et al., 1982; Gendolla and Richter, in

press; Tranel et al., 1982; Wright et al., 2002; Wright et al.,

1995, Experiment 2). Especially, systolic blood pressure (SBP)

reactivity has been demonstrated to reflect this pattern well

(e.g., Bongard, 1995; Gendolla and Krusken, 2001a,b,

2002b,c; Gerin et al., 1995; Light, 1981; Lovallo et al.,

1985; Obrist, 1981; Sherwood et al., 1990; Smith et al., 1997,

2000). Evidence for heart rate (HR) and diastolic blood

pressure (DBP) reactivity is less consistent but existent

siology 61 (2006) 216 – 225

www.else

mailto:[email protected]

http://dx.doi.org/10.1016/j.ijpsycho.2005.10.003

M. Richter, G.H.E. Gendolla / International Journal of Psychophysiology 61 (2006) 216–225 217

(Gendolla and Krusken, 2001b; Gendolla and Richter, in press;

Obrist, 1981; Schwerdtfeger, 2004; Storey et al., 1996).

In contrast to the vast bulk of research on CV reactivity

under conditions of fixed and unfixed task difficulty, research

involving tasks with fixed, but unclear task difficulty is rare.

So far, only one unpublished study has directly addressed this

issue. Participants in an experiment by Wright, Heaton, and

Bushman (reported in Wright and Brehm, 1989) expected to

perform a memory task and were either informed that they

would face an easy task (clear difficulty) or one of five tasks,

which differed in difficulty (unclear difficulty). As predicted by

the integrative analysis of CV response in active coping

(Wright, 1996), SBP was directly determined by the incentive

presented for successful task performance (either a music

record or a pen) only when participants did not know the exact

difficulty level of their task: Systolic reactivity was stronger

when participants could win the relatively valuable record than

when they could win the less valuable pen. When task

difficulty was known, SBP reactivity was low, corresponding

to the low task difficulty, and not influenced by incentive value.

However, although these results seem to be clear, this

experiment unfortunately suffers from two shortcomings. First,

the study only assessed anticipatory CV responses before task

performance. Thus, effects of unclear difficulty during perfor-

mance remain open. Second, the possibility remains that

systolic reactivity in the unclear/record group did not reflect

the level of potential motivation, but the resources necessary

to cope with the highest task demand participants could expect

to perform. Thus, Wright et al.’s experiment is open to

alternative interpretations because it did not involve a direct

manipulation of unclear task difficulty.

The same ambiguity applies to earlier studies that were

conducted outside the conceptual frame of motivational

intensity theory (Belanger and Feldman, 1962; Fowles et al.,

1982; Hahn et al., 1962; Tranel et al., 1982), but which have

been quoted as evidence for unfixed difficulty effects (see

Wright et al., 2002). Because these studies did not involve

any direct manipulation of the clarity of task difficulty, they

can also be interpreted as reflecting resource mobilization

processes under conditions of unclear task difficulty. It remains

open if CV responses were due to unfixed or due to unclear

task difficulty. Thus, to date no crucial test exists of the

predicted relationship between success importance and CV

reactivity in active coping tasks with unclear task difficulty,

which assessed CV responses during task performance.

2. The present experiments

The present experiments aimed to close the gap in evidence

for the predictions of motivational intensity theory regarding

unclear task difficulty. Therefore, two experiments investigat-

ed CV reactivity in the context of a memory task that was

either easy (Experiment 1) or extremely difficult (Experiment

2). To manipulate the clarity of task difficulty, half the

participants in each experiment were informed about the exact

level of task difficulty (clear difficulty); the other half

remained uninformed (unclear task difficulty). To test the

hypothesis about the joint impact of the clarity of task

difficulty and success importance, we simultaneously manip-

ulated incentive value – one determinant of success impor-

tance – by promising and presenting different rewards for

successful task performance (two pictures differing in their

attractiveness in Experiment 1; different amounts of money in

Experiment 2). Based on the psychophysiological literature

(e.g., Belanger and Feldman, 1962; Bongard, 1995; Fowles et

al., 1982; Gendolla and Krusken, 2001a,b, 2002b,c; Gerin et

al., 1995; Hahn et al., 1962; Light, 1981; Lovallo et al., 1985;

Obrist, 1981; Sherwood et al., 1990; Smith et al., 1997, 2000;

Tranel et al., 1982) and the predictions of motivational

intensity theory for unclear and fixed task difficulty, we

expected that (1) CV reactivity should vary directly with

incentive value under conditions of unclear task difficulty. The

exact level of difficulty should be unimportant. By contrast,

we predicted (2) under clear task difficulty, low and equal CV

reactivity independent of incentive value either due to low

task difficulty (Experiment 1) or due to too high task difficulty

(Experiment 2).

2.1. Experiment 1

Participants performed an easy memory task in which

success was rewarded with a poster gift that was either

attractive or unattractive. Task difficulty was either easy and

clear or easy and unclear. SBP, DBP, and HR were assessed

before and during task performance to determine CV reactivity.

Based on our theoretical reasoning, we expected high CV

reactivity (especially SBP) only in the unclear/attractive

condition. In the other three conditions CV reactivity should

be equally modest.

2.1.1. Method

2.1.1.1. Participants and design. Forty-four university stu-

dents with various majors (psychology excluded, 33 women

and 11 men) participated in the experiment. They were

randomly assigned to a 2 (clarity of task difficulty: clear vs.

unclear)�2 (reward attractiveness: attractive vs. unattractive)

between-persons design and received 5 euros (about 6 US$) for

their anonymous and voluntary participation. The distribution

of women and men was balanced between the conditions.

2.1.1.2. Apparatus and physiological measurement. SBP (in

millimeter mercury [mmHg]), DBP (in millimeter mercury

[mmHg]), and HR (in beats per minute [bpm]) were measured

with a computer-aided multi-channel monitor (Par Electronics

Physioport III) via the oscillometric method. A blood pressure

cuff (Boso) was placed over the brachial artery above the

elbow of the participants’ left arm and automatically inflated

in 1-min intervals during 2 measurement periods: habituation

and task performance. The obtained measures were stored on a

computer disk. Both the participants and the experimenter

(who was hired and ignorant of both the hypotheses and the

particular experimental condition) were ignorant of all values

obtained during the experimental session. The entire experi-

M. Richter, G.H.E. Gendolla / International Journal of Psychophysiology 61 (2006) 216–225218

ment was run on a personal computer using experiment

generation software (INQUISIT, Millisecond Software).

2.1.1.3. Procedure. Participants arrived individually and took

a seat in front of a personal computer. After application of the

blood pressure cuff and starting of the computer program,

participants answered some biographical questions. During the

following habituation period of 10 min participants read an old

issue of a magazine while 8 CV measures were taken in 1-min

intervals. After this habituation period participants received

instructions for the memory task.

2.1.1.3.1. Memory task and clarity of difficulty manipula-

tion. We used a slightly modified version of a memory task,

which has already been successfully administered in previous

studies on CV reactivity (e.g., Gendolla and Krusken, 2002a,

Experiment 1, 2002c). Participants had to memorize within

5 min a list of 4 senseless letter series (ALMP, EPQZ, TSAM,

CLTW) and to correctly recall the series at the end of the

performance period. Instead of presenting all series at the

same time, the letter series occurred successively in 75-s

intervals. That is, at the beginning of task performance only

the first group of four letters (ALMP) was visible on the

monitor screen. After 75 s the second group (EPQZ)

appeared, after 150 s the third letter group emerged (TSAM),

and 75 s before the end of the performance period all of the 4

series were visible on the screen. All participants were

informed about the presentation procedure of the letter series,

but only participants in the clear task difficulty condition

received information concerning the exact number of letter

series, the total performance time, and the time interval

between the appearances of the different letter series.

Participants in the unclear task difficulty condition were only

informed that several letter series would be presented

successively on the screen but they did not receive any

information about the difficulty of the memory task. By

choosing a successive presentation procedure, we tried to

establish a condition where task difficulty remained unclear as

long as possible.

2.1.1.3.2. Incentive manipulation. Following task instruc-

tions, all participants were informed that they could win a

poster as reward for successfully memorizing all of the letter

series that would be presented. For participants in the

unattractive reward condition, this was a technical poster of a

caterpillar; for participants in the attractive reward condition, it

was a poster of van Gogh’s ‘‘Cafe de Nuit’’ painting.

According to a pre-study with 40 participants, both posters

differed not only in their attractiveness but also in their

incentive value as well, t values (36) >6.54, p values <.001.

Attractiveness (‘‘How attractive does the picture appear to

you?’’) was assessed on a scale ranging from unattractive (1) to

attractive (9) (mean=6.33, S.E.M.=0.25 for the ‘‘Cafe de

Nuit’’ and mean=2.20, S.E.M.=0.27 for the caterpillar).

Incentive value (‘‘How much effort would you invest to get a

poster of the presented picture?’’) was assessed on a scale

ranging from very few (1) to very much (9) (mean=5.25,

S.E.M.=0.40 for the ‘‘Cafe de Nuit’’ and mean=1.86,

S.E.M.=0.28 for the caterpillar).

After the manipulation of the clarity of task difficulty and

reward attractiveness, participants rated the attractiveness of

the presented poster (‘‘How attractive does the poster appear to

you?’’) and their interest in winning the poster (‘‘How

interested are you in winning the presented poster?’’) on two

scales ranging from, respectively, unattractive and not at all

interested (1) to, respectively, attractive and very interested

(9). Furthermore, participants in the clear difficulty condition

rated task difficulty (‘‘How difficult does the task appear to

you?’’) on a scale ranging from very easy (1) to very difficult

(9). We decided not to include the difficulty rating in the

unclear conditions to prevent focusing participants on task

difficulty. This could have forced the participants to artificially

construct a difficulty impression of the task (e.g., Gendolla and

Richter, in press). Following these ratings, participants worked

on the task for 5 min, while 5 CV measures were taken in

1-min intervals, starting 15 s after task onset. After the

performance period participants noted the letter series, they

could recall on a prepared sheet of paper. Finally, participants

were probed for suspicion, debriefed, and given their payment.

2.1.2. Results

2.1.2.1. Preliminary analyses. Preliminary 2 (clarity of task

difficulty)�2 (reward attractiveness)�2 (gender) ANOVAs

found gender main effects on the baseline values of all three

CV indices (all p values< .03). CV baselines were higher for

men (mean=80.89, S.E.M.=3.16 for HR; mean=126.86,

S.E.M.=5.39 for SBP; mean=81.17, S.E.M.=5.70 for DBP)

than for women (mean= 72.69, S.E.M. = 0.45 for HR;

mean = 109.78, S.E.M. = 1.43 for SBP; mean = 72.35,

S.E.M.=1.12 for DBP). Gender had no significant influence

on cardiovascular reactivity (all p values> .06).

2.1.2.2. Difficulty and attractiveness manipulation. Analyz-

ing our two measures of incentive value – which were highly

correlated (r = .65, p < .001) – with a 2 (clarity of task

difficulty)�2 (reward attractiveness) multivariate ANOVA

showed only the expected effect for reward attractiveness,

F(2,39)=18.85, p <.001 (all other p values> .50). Furthermore,

univariate analyses revealed that only reward attractiveness had

a significant effect on both ratings, F(1,40)>12.16, p< .002 (all

other p values> .39). Participants rated the picture as more

attractive and were more interested in winning a poster of the

picture when they could win the ‘‘Cafe de Nuit’’ (mean=5.68,

S.E.M. = 0.59 for attractiveness ratings; mean = 4.32,

S.E.M.=0.58 for interest ratings) than when they could win

the caterpillar picture (mean=1.77, S.E.M.=0.22 for attrac-

tiveness ratings; mean=2.00, S.E.M.=0.29 for interest ratings).

Furthermore, a one-sample t-test revealed that participants’

ratings of task difficulty in the clear condition (mean=4.14,

S.E.M.=0.30) were significantly lower than 5, the scale’s mid

point, t(21)=2.91, p <.01. This indicates that the task was

indeed perceived as easy.

2.1.2.3. CV baselines. CV baseline scores for HR, SBP, and

DBP were computed using the arithmetic mean of the last three

Table 1

Cell means and standard errors of mean of the cardiovascular baseline values in

Experiment 1

Mean S.E.M.

Clear

difficulty

Unclear

difficulty

Clear

difficulty

Unclear

difficulty

SBP

Attractive reward 107.70 115.26 2.80 3.31

Unattractive reward 121.67 111.58 5.58 3.15

DBP



HR



n =11 in each cell. SBP=systolic blood pressure, DBP=diastolic blood

pressure, HR=heart rate. SBP and DBP are in mmHg; HR is in bpm.


measures taken during the habituation period (Cronbach’s avalues were .85 for HR baseline, .94 for SBP baseline, and .58

for DBP baseline).1 2 (clarity of task difficulty)�2 (attrac-

tiveness) between-persons ANOVAs of the baseline measures

of SBP and DBP found significant interactions between clarity

of difficulty and reward attractiveness, F(1,40)>5.20, p <.03

(all other p values> .19). This effect is hardly explainable from

a theoretical perspective since clarity of task difficulty and

reward attractiveness were manipulated after baseline record-

ings. However, we dealt with these findings in the analyses of

the reactivity scores by analyzing baseline-adjusted reactivity

scores of SBP and DBP. A 2 (clarity of difficulty)�2 (reward

attractiveness) ANOVA of HR baseline values revealed no

differences between the four experimental conditions (all

p values> .37). Means and standard errors of the baseline

values of all CV measures are presented in Table 1.

2.1.2.4. CV reactivity. We computed CV change (delta-)

scores (Llabre et al., 1991) for each participant and each CV

measure by subtracting the baseline value from the arithmetic

mean of the values obtained during task performance (Cronba-

ch’s a values were .94 for HR performance values, .94 for SBP

performance values, and .87 for DBP performance values).

Based on our clear predictions about the joint effect of clarity of

task difficulty and reward attractiveness on CV reactivity, we

analyzed the reactivity scores with a priori contrasts (Rosenthal

and Rosnow, 1985). Contrast weights were +3 for the unclear/

attractive cell and �1 for the remaining three conditions.

Furthermore, we investigated the relationship between baseline

values and reactivity scores for each parameter. If there were

any associations, we used baseline-adjusted reactivity scores in

our analyses to prevent for initial value or carry-over effects (see

Benjamin, 1967; Llabre et al., 1991).

1 We formed the cardiovascular baseline values of the last three measures,

because for all three cardiovascular parameters, the measures decreased over

the first baseline measures and only the last three measures did not differ

significantly from one another (all p values>0.16).

2.1.2.4.1. SBP reactivity. Because SBP baseline values

differed between the conditions and were significantly corre-

lated with SBP reactivity scores (r =� .45, p <.01), we included

the baseline values as covariate in the analysis of the SBP

reactivity scores. The effect of the covariate was significant,

F(1,39)=13.03, p <.002. The a priori contrast was significant as

well, F(1,39)=5.56, p <.03, MSE=39.04, and the non-signif-

icant effect for the residual (F <1) indicated that the contrast

captured all significant variance. We further explored the pattern

of systolic reactivity with focused contrasts.2 Cell means and

standard errors of the baseline-adjusted reactivity scores are

depicted in Fig. 1. As anticipated, SBP reactivity in the unclear/

attractive cell (mean=6.10, S.E.M.=1.65) was significantly

stronger than in the unclear/unattractive (mean = 1.04,

S.E.M.=1.79) and the clear/attractive condition (mean=�0.51,0.51, S.E.M.=1.26), t(39)>1.89, p values< .04. The difference

between the unclear/attractive and the clear/unattractive condi-

tion (mean=2.23, S.E.M.=2.52) approached significance,

t(39)=1.43, p <.09. All other focused comparisons were not

significant ( p values> .34). In summary, this demonstrates that

SBP reactivity reflected the predicted 1:3 pattern, as can be also

seen in Fig. 1.

2.1.2.4.2. DBP reactivity. To account for the difference

between the conditions in DBP baseline values and the

significant association of DBP baseline with DBP reactivity

scores (r =.79, p <.001), we analyzed baseline-adjusted reac-

tivity scores. Cell means and standard errors appear in Table 2.

The effect for the covariate was reliable, F(1,39)=60.41,

p <.001, but the effect for the a priori contrast was not,

F(1,39)=2.57, p >.11, MSE=42.57.

2.1.2.4.3. HR reactivity. We analyzed raw reactivity scores

(see Table 2), because the association between baseline values

and reactivity scores was not reliable (r =� .16, p> .30) and

baseline values did not differ between the conditions. However,

the a priori contrast was not significant, F(1,40)=0.14, p >.50,

MSE=15.11.

2.1.2.5. Task performance. As performance indicators we

examined the number of recalled letter series and the number of

correctly recalled letter series with two 2 (clarity of

difficulty)�2 (reward attractiveness) ANOVAs. For the

number of totally noted letter series (mean=3.82, S.E.M.=

0.09), no effect was significant (all p values> .34). For the

number of correctly recalled letter series, only the interaction

between clarity of difficulty and reward attractiveness was

reliable, F(1,40) =4.69, p < .04, MSE=0.59 (all other p

values> .33). Simple effects analyses comparing the four

experimental groups revealed that reward attractiveness had

only a significant effect on performance when task difficulty

was unclear, F(1,40)=4.96, p <.03: Participants in the unclear/

unattractive condition (mean=3.91, S.E.M.=0.09) memorized

more items correctly than participants in the unclear/unattrac-

tive condition (mean=3.18, S.E.M.=0.26). All other compar-

2 Given our directed a priori hypothesis, we used one-tailed tests for the

comparison of the unclear/attractive condition with each of the other three

conditions.

SBP Reactivity

unclear clear

SB

P r

espo

nse

(mm

Hg)

-3

-2

-1

0

1

2

3

4

5

6

7

8 attractive rewardunattractive reward

Fig. 1. Baseline-adjusted cell means and standard errors of systolic blood

pressure (SBP) reactivity during task performance in Experiment 1.

mmHg=millimeter mercury.

Table 2

Cell means and standard errors of mean of baseline-adjusted DBP and HR

reactivity in Experiment 1

Mean reactivity score S.E.M.

Clear

difficulty

Unclear

difficulty

Clear

difficulty

Unclear

difficulty

DBP reactivitya


Unattractive reward �2.95 �0.38 2.00 1.98

HR reactivity



n =11 in each cell. DBP=diastolic blood pressure, HR=heart rate. DBP is in

mmHg; HR is in bpm.a Baseline-adjusted.


isons were not significant (all p values> .10; mean=3.73 and

S.E.M.=0.27 for the clear/unattractive cell; mean=3.45 and

S.E.M.=0.25 for the clear/attractive cell). We further examined

the data for reliable associations between reactivity scores and

performance values. The only significant effect was a

correlation between baseline-adjusted SBP reactivity scores

and both number of correctly and number of totally recalled

letter series, .30< r values< .38, p values< .05 (all other

p values> .08), reflecting a reliable association between effort

and achievement.

2.1.3. Discussion

The presented experiment investigated CV reactivity in an

easy memory task under clear or unclear task difficulty.

Supporting the predictions of motivational intensity theory

(Brehm and Self, 1989) and Wright’s (1996) integrative

analysis, systolic reactivity differed only in dependence on

the attractiveness of the reward when task difficulty was

unclear: When participants could win the attractive poster

‘‘Cafe de Nuit’’, SBP reactivity was stronger than when

participants could win the less attractive caterpillar picture.

By contrast, when task difficulty was clear, systolic reactivity

was low independent of incentive value, reflecting solely the

low task demand. HR and DBP reactivity effects were not

significant, although DBP reactivity resembled the 1:3 pattern

of systolic reactivity.

However, this does not qualify the results with regard to the

predictions of motivational intensity theory for resource

mobilization under unclear task difficulty. According to

Wright’s (1996) integration of motivational intensity theory

(Brehm and Self, 1989) with Obrist’s (1981) active coping

approach, energy mobilization should be reflected by the

impact of the sympathetic nervous system on the heart and the

vasculature. Since SBP is more systematically influenced by

sympathetic discharge to the heart than DBP and HR (Berne

and Levy, 1977; Brownley et al., 2000; Levick, 2003; Obrist,

1981; Papillo and Shapiro, 1990; Wright, 1996), SBP should

be the most sensitive measure of energy mobilization among

these three cardiovascular indices – as it was in the present

experiment. However, there is evidence for DBP responses in

active coping as well (Al’Absi et al., 1997; Gendolla, 1999;

Gendolla and Richter, in press; Gerin et al., 1995; Lovallo et al.,

1985; Smith et al., 1990; Storey et al., 1996; Wright and Dill,

1993). These effects might be due to greater vasoconstriction

than vasodilation (e.g., Storey et al., 1996) or due to especially

strong myocardioal contractility resulting in parallel increases

in SBP and DBP (e.g., Lovallo et al., 1985; Sherwood et al.,

1990). Given that we did not assess myocardial contractility or

peripheral resistance directly in this experiment, further

research is needed to understand the DBP effects. Moreover,

since we did not directly assess sympathetic or parasympathetic

functioning, our reflection on the mediating mechanisms of the

CV effects rests speculative.

Nevertheless, it should be noted, that the effects on DBP do

not contradict our predictions. There is further evidence that

SBP reactivity indeed reflected the mobilization of mental

effort in the memory task. SBP reactivity was not only

significantly correlated with memory performance, even the

number of correctly recalled letter series reflected the

difference in energy mobilization between participants who

could win the attractive reward and participants who could only

win the unattractive reward. Participants in the unclear/

attractive condition showed greater SBP reactivity and recalled

more letter series correctly than participants in the unclear/

unattractive condition.

In summary, the results clearly supported our predictions.

Only when participants had no information about task

difficulty, success importance – which was higher in the case

of an attractive reward than for the unattractive reward as

indicated by the significant manipulation check – directly

determined resource mobilization. When the low task diffi-

culty was clear, resource mobilization was not affected by

incentive value. To conceptually replicate these new results,

we conducted a second experiment investigating the moder-

ating effect of the clarity of task difficulty and incentive value

on CV responses in an extremely difficult memory task.

Furthermore, we used a monetary reward instead of a poster to

show that the effects are not limited to a certain type of

incentive.

SBP Reactivity

unclear clear

SB

P r

espo

nse

(mm

Hg)

0123456789

10111213 reward

no reward

Fig. 2. Baseline-adjusted cell means and standard errors of systolic blood

pressure (SBP) reactivity during task performance in Experiment 2.

mmHg=millimeter mercury.


2.2. Experiment 2

Participants performed an extremely difficult memory task,

either knowing (clear difficulty) or not knowing (unclear

difficulty) the exact level of task difficulty. Half of the

participants could win 10 Swiss Francs (about 7 US$) by

successfully performing the task (reward condition). For the

other half, there was no reward for successful task perfor-

mance. To assess CV reactivity, CV measures were taken

before and during task performance. Based on the predictions

of motivational intensity theory, we predicted relatively high

CV reactivity (especially SBP) in the unclear/reward condition

and low CV reactivity in the other three conditions.

2.2.1. Method

2.2.1.1. Participants and design. Forty-eight university

students with various majors (31 women and 17 men)

participated anonymously and voluntarily in the experiment

for course credit. They were randomly assigned to a 2 (clarity

of task difficulty: clear vs. unclear)�2 (incentive: reward vs.

no-reward) between-persons design. The distribution of women

and men was balanced across the experimental conditions.

2.2.1.2. Apparatus and procedure. Apparatus and basic

experimental procedure were identical with Experiment 1.

Following the application of the blood pressure cuff and the

collection of biographical data, the multi-channel monitor took

6 CV baseline measures in 1-min intervals, starting 3 min after

the beginning of the habituation period. Then participants

received instructions for the memory task, which was the same

as in Experiment 1, except the number of letter series

participants had to memorize within 5 min. Instead of

presenting 4 letter series, we now presented a list of 30 letter

series. In pre-tests, nobody had been able to memorize the

majority of the items in 5 min. Because of the higher number of

letter series, the single items appeared now in 10-s intervals. As

in Experiment 1, all participants were informed that they would

Table 3

Cell means and standard errors of mean of the cardiovascular baseline values in

Experiment 2

Mean baseline score S.E.M.

Clear

difficulty

Unclear

difficulty

Clear

difficulty

Unclear

difficulty

SBP

Reward 111.61 107.65 3.18 4.06

No reward 103.83 103.60 2.69 2.52

DBP

Reward 68.50 68.00 2.24 4.86

No reward 66.17 67.69 2.40 2.40

HR

Reward 76.22 76.63 2.93 2.38

No reward 73.34 73.88 1.46 0.97

n=12 in each cell. SBP=systolic blood pressure, DBP=diastolic blood

pressure, HR=heart rate. SBP and DBP are in mmHg; HR is in bpm.

have to work on the memory task for a certain time and that

they should try to memorize all of the successively presented

letter series, but only participants in the clear difficulty

condition received exact information concerning task difficulty.

2.2.1.3. Incentive manipulation. After task instructions parti-

cipants in the reward condition were informed that they could

win 10 Swiss Francs by memorizing all of the presented letter

series. Trying to increase the difference in incentive value

between both reward conditions compared to Experiment 1, no

reward was offered in the no-reward condition After the

manipulation of clarity of task difficulty and incentive,

participants judged the attractiveness (‘‘How attractive does

task success appear to you?’’) and the importance of success

(‘‘How important is it for you to successfully perform the

memory task?’’) on two scales ranging from, respectively,

unattractive and not important at all (1) to, respectively,

attractive and very important (9). Furthermore, participants in

the clear difficulty conditions rated task difficulty (‘‘How

difficult does the task appear to you?’’) on a scale with the

anchors very easy (1) and very difficult (9).

After these ratings, participants performed the memory task

for 5 min, while 5 CV measures were taken in 1-min intervals.

At the end of the performance period, participants noted the

letter series they had memorized. Finally, participants were

probed for suspicion and carefully debriefed.

2.2.2. Results

2.2.2.1. Preliminary analyses. As in Experiment 1, prelim-

inary analyses found a significant gender main effect on the

SBP baseline values, F(1,40)=6.30, p <.02, MSE=99.19,

which were higher for men (mean=111.97, S.E.M.=3.11)

than for women (mean=103.77, S.E.M.=1.62). Unexpectedly,

we found a significant gender� incentive interaction on SBP

baselines and a significant gender�clarity of difficulty

interaction on HR reactivity, as well (both p values< .03) (all

other p values> .07). We will deal with the latter in the analysis

of HR reactivity.

Table 4

Cell means and standard errors of mean of baseline-adjusted DBP and HR

reactivity in Experiment 2

Mean reactivity score S.E.M.

Clear

difficulty

Unclear

difficulty

Clear

difficulty

Unclear

difficulty

DBP reactivitya

Reward �0.90 7.57 1.49 2.53

No reward 1.47 1.40 2.09 1.72

HR reactivity

Reward 1.83 4.92 1.64 1.76

No reward 1.86 2.71 0.85 1.76

n =12 in each cell. DBP=diastolic blood pressure, HR=heart rate. DBP is in

mmHg; HR is in bpm.a Baseline-adjusted.


2.2.2.2. Difficulty and reward manipulation. As in Experi-

ment 1, we analyzed our indicators of incentive value – the

attractiveness and the importance ratings – with a 2 (clarity of

difficulty)�2 (incentive) multivariate ANOVA and found the

expected incentive main effect, F(2,43)=5.47, p <.009 (all

other p values> .06). However, in univariate analyses, no effect

was significant (all p values> .09).

The analysis of the difficulty ratings in the clear difficulty

conditions with a one sample t-test revealed that participants’

ratings differed significantly from the scale mean of 5,

t(23)=3.16, p <.005 (mean=5.65, S.E.M.=0.21). Thus, as

intended, the task was perceived as demanding.

2.2.2.3. CV baselines. The arithmetic mean of the last three

measures of HR, SBP, and DBP during habituation constituted

our CV baseline measures (Cronbach’s a values were .96 for

HR baseline, .94 for SBP baseline, and .93 for DBP baseline).3

2 (clarity of difficulty)�2 (incentive) ANOVAs of these

baseline measures found no significant differences between

the conditions (all p values> .06). Cell means and standard

errors are presented in Table 3.

2.2.2.4. CV reactivity. We computed CV change (delta-)

scores (Llabre et al., 1991) for each participant by subtracting

the baseline values from the averages of the values obtained

during task performance (Cronbach’s a values were .97 for HR

performance values, .96 for SBP performance values, and .93

for DBP performance values). Based on our clear theory-based

predictions concerning the joint impact of the clarity of task

difficulty and incentive value on CV reactivity, we used a priori

contrasts (Rosenthal and Rosnow, 1985) to analyze the

reactivity scores. Contrast weights were +3 for the unclear/

reward cell and �1 for each of the remaining three cells. If

there was any association between baseline values and

3 For the sake of consistency between the two experiments, we used the last

three measures for the computation of baseline measures. Conducting the

analyses with a baseline measure that includes only the last two measures—HR

and DBP significantly decreased over the first four baseline measures and only

the last two measures did not differ from one another ( p values>0.21)—did

not change the statistical results.

reactivity scores, we corrected the reactivity scores with regard

to the baseline values.

2.2.2.4.1. SBP reactivity. SBP baseline values were

correlated with SBP reactivity scores (r =� .36, p <.02). Thus,we included the baseline values as covariate in the analysis of

the SBP reactivity scores. Both the effect for the covariate,

F(1,43)=7.51, p <.01, and the a priori contrast, F(1,43)=9.99,

p <.004, MSE=52.01, were significant. The residual was not

significant (F <1). We further investigated the pattern of

systolic reactivity with focused cell-contrasts.4 As can be seen

in Fig. 2, the pattern of baseline-adjusted systolic reactivity

corresponded to our predictions. SBP reactivity in the unclear/

reward cell (mean=10.33, S.E.M.=2.08) was significantly

stronger than in the unclear/no-reward condition (mean=1.97,

S.E.M. = 2.10), the clear/reward cell (mean = 1.98,

S.E.M.=2.14), and the clear/no-reward condition (mean=4.24,

S.E.M.=2.10), t values (43)>2.07, p values< .03. No other cell

comparison was significant ( p values> .44).

2.2.2.4.2. DBP reactivity. Because the DBP baseline

values were significantly correlated with DBP reactivity scores

(r =� .55, p < .001), we analyzed baseline-adjusted DBP

reactivity scores. The effect of the covariate was significant,

F(1,43) = 22.64, p < .001, as was the a priori contrast,

F(1,43)=8.80, p <.006, MSE=48.91. The test for the residual

was not significant (F <1). The following focused comparisons

revealed that DBP reactivity showed the same 1:3 pattern as

SBP reactivity — as can be seen in Table 4. DBP reactivity in

the unclear/reward condition was significantly stronger than

DBP reactivity in the other three cells, t(43) > 2.13,

p values< .02. All other focused comparisons were not

significant ( p values> .41).

2.2.2.4.3. HR reactivity. HR baseline and reactivity values

were not reliably associated (r =� .20, p >.17). Thus, raw HR

reactivity scores were analyzed. The a priori contrast was not

significant, F(1,44)=2.42, p >.12, MSE=28.83. However, as

can be seen in Table 4, HR reactivity showed the expected

1:3 pattern. Because of the significant influences of gender on

HR reactivity scores, we tested for an interaction between our a

priori contrast and gender. This analysis revealed that gender

did not moderate the joint influences of clarity of task difficulty

and incentive on CV reactivity, t(5.966)=1.96, p >.09.5

2.2.2.5. Task performance. As in the first study, the total

number of recalled letter series and the number of correctly

recalled letter series were analyzed with 2 (clarity of

difficulty)�2 (incentive) ANOVAs. However, no significant

effects emerged (all p values> .15). On average, participants

noted mean=4.75 letter series (S.E.M.=0.37) and correctly

recalled mean=2.52 letter series (S.E.M.=0.34). Furthermore,

neither the number of totally recalled letter series, nor the

numbers of correctly recalled letter series were significantly

4 Given our clear directed a priori hypothesis, one-tailed tests were used for

the comparison of the unclear/reward condition with the other three conditions5 Corrected degrees of freedom were used for the test because variances were

not homogeneously distributed.

.


associated with CV reactivity (� .22 < r values < .05,

p values> .15).

2.2.3. Discussion

Experiment 2 replicated and extended the results of

Experiment 1, supporting again the predictions of motivational

intensity theory (Brehm and Self, 1989) and its integration with

Obrist’s (1981) active coping approach to cardiovascular

arousal by Wright (1996). As in Experiment 1, systolic

reactivity varied only in the unclear difficulty conditions in

dependence on incentive value: When participants could earn

the monetary reward of 10 Swiss Francs by successfully

performing the demanding memory task, systolic reactivity

was stronger than when participants could not win the

monetary reward. In the clear difficulty condition, systolic

reactivity was low and did not differ between the incentive

conditions. Also DBP and HR reactivity showed the same

1:3 pattern. However, the pattern of the latter did not reach

the level of significance and involved gender differences.

One shortcoming of this study, however, that is of minor

importance might be that the incentive value manipulation was

only reflected on the multivariate level and not as pronounced

on the single ratings. One may speculate that a reward of

10 Swiss Francs is perhaps not high enough to result in

noticeable effects on subjective reports of success importance,

but high enough to result in an increase in incentive value.

However, it is also clear that self-report measures have their

own problems (see Wilson and Dunn, 2004) and that zero-

effects can have multiple reasons. Another reason for the zero

effects in Experiment 2 might have been that we changed our

questions assessing success importance. Questions in Experi-

ment 1 were more directly related to incentive characteristics of

the reward (‘‘How attractive does the poster appear to you?’’

and ‘‘How interested are you in winning the presented

poster?’’) whereas questions in Experiment 2 (‘‘How attractive

does task success appear to you?’’ and ‘‘How important is it for

you to successfully perform the memory task?’’) were more

strongly related to incentive characteristics of success. Perhaps

participants in Experiment 2 felt that they could appear as lazy

if they indicate that success is not attractive or important for

them. As a result, they may have tried to prevent low ratings on

both questions. More important than a significant verbal

manipulation check is the predicted significant effect on the

dependent measure – CV reactivity – and that there is no

plausible alternative explanation that could account for the

pattern of SBP reactivity better than an effective manipulation

of incentive value combined with clear vs. unclear task

difficulty (see Sigall and Mills, 1998).

One might wonder that difficulty ratings of participants in

the clear task difficulty conditions were not as high as one

could expect. Ratings were clearly higher than the scale mean,

but differed from the scale endpoint of nine, as well. Multiple

reasons could account for the finding that difficulty ratings did

not reflect objective task difficulty. For instance, participants

might have tended to avoid extreme ratings, especially ratings

of extreme difficulty. It might have been difficult for

participants to imagine the difficulty of learning 30 letter

series within 5 min. Therefore, one should not conclude based

on difficulty ratings alone that the task was not very difficult.

Compared to other difficulty levels of the memory task,

which have been used in previous studies (e.g., Gendolla and

Krusken, 2002a,c), the task we have administered in this study

was indeed extremely difficult. Furthermore, it is obvious that

it is very difficult, maybe even impossible, to learn correctly

30 letter series within 5 min. Even if one underestimates task

difficulty at the beginning of the memory task, after the rapid

successive presentation of the first letter series it becomes clear

that it will be very hard to succeed in this task. Thus, task

difficulty ratings did not limit our interpretations.

In summary, Experiment 2 further supported the predictions

of motivational intensity theory (Brehm and Self, 1989) for

unclear task difficulty. Incentive value affected SBP responses

only when difficulty was unknown. When participants had

received information about the difficulty of the memory task,

they mobilized only little resources because the level of

necessary effort exceeded their level of incentive value in both

incentive conditions. Furthermore, Experiment 2 extended the

results of Experiment 1 by demonstrating that SBP responses

are also proportional to incentive value when task difficulty of

an extremely difficult task is unknown. Although success was

impossible, participants invested relatively high resources

when they were ignorant of task difficulty and performance-

contingent incentive was high.

3. General discussion

Two experiments investigated CV reactivity as an indicator

of resource mobilization in the context of a memory task with

either unclear or clear task difficulty. By administering an easy

(Experiment 1) and a very difficult memory task (Experiment

2), we investigated two difficulty levels that are important from

a theoretical point of view. For both low and extremely high

difficulties, we found the expected moderation of CV responses

by clarity of task difficulty. When task difficulty was unclear,

incentive value directly determined systolic reactivity: Mone-

tary reward or an attractive poster resulted in stronger systolic

and diastolic reactivity (Experiment 2) compared to no reward

or a less attractive prize. When task difficulty was clear,

participants did not invest any effort due to low task difficulty

(Experiment 1) or because of incentive value falling short of

the effort necessary to cope with the demanding task

(Experiment 2). As could be expected for physiological reasons

(Wright, 1996), the reactivity pattern was the most pronounced

for systolic reactivity. However, comparable with preceding

experiments (e.g., Bongard and Hodapp, 1997; Lovallo et al.,

1985; Smith et al., 1990), the pattern of DBP and HR

(Experiment 2) reactivity at least resembled the pattern of

SBP reactivity.

In summary, the pattern of CV reactivity clearly supported

the predictions of motivational intensity theory (Brehm and

Self, 1989) for unclear task difficulty. The experiments thus

make an important contribution to close a gap in the empirical

support for this approach. So far, researchers have investigated

the predictions of this model only for fixed and unfixed task


difficulty (see Richter et al., in press; Wright, 1996; Wright and

Kirby, 2001 for reviews) and did not pay much attention to CV

responses in tasks with unclear difficulty. Preceding relevant

experiments did either not include a direct manipulation of the

clarity of task difficulty (e.g., Elliot, 1969; Fowles et al., 1982;

Tranel et al., 1982) or they did only assess CV responses

immediately prior to but not during task performance (Wright

et al., reported in Wright and Brehm, 1989). Our experiments

demonstrate for the first time that CV reactivity during active

coping is directly determined by incentive value under

conditions of unclear task difficulty.

But the results of our experiments go also beyond supporting

motivational intensity theory. They offer an alternative account

for the results of earlier studies, which found a positive

association between CV responses and incentive value (e.g.,

Elliot, 1969; Fowles et al., 1982; Tranel et al., 1982). So far, the

common explanation in terms of motivational intensity theory

was the unfixed difficulty hypothesis: CV reactivity varies in

dependence on incentive value due to unfixed task difficulty. The

present results make it also plausible that this covariation was

caused by unclear task difficulty. Probably, in all of these

experiments, the exact level of task difficulty was unknown for

participants. Consequently, success importance directly deter-

mined task engagement. In particular, this explanation fits well

with Elliot’s (1969) experiment. In that study, CV responses

showed a proportional relationship with incentive value during

the first trials in the performance period. During later trials CV

responses were dissociated from incentive value. Possibly,

participants formed an impression of task difficulty during the

first trials and did not have to rely any longer on incentive value

as indicator of resource mobilization. Thus, the unclarity

hypothesis seems to be an explanation for these earlier studies,

which is as plausible as the unfixed hypothesis.

The present findings for task performance were in accor-

dance with previous research, which has shown that CV

reactivity and task performance are only loosely connected

(e.g., Gendolla et al., 2001). Only in Experiment 1 we found a

positive association between systolic reactivity and the number

of memorized letter series. Furthermore, performance values

reflected that participants in the unclear/attractive condition did

not only work harder but also more reliable than participants in

the unclear/unattractive condition. In Experiment 2, we could

neither replicate any of these effects, nor observe any

relationship between resource mobilization and achievement.

However, because task performance is not a direct function of

effort but a product of ability, strategy, and effort (Locke and

Latham, 1990), this is not surprising. Effects of ability or

strategy can mask the relationship between effort and

achievement and explain why researchers sometimes find an

association between effort and achievement and sometimes not.

Furthermore, there is evidence that tasks that rely more

strongly on attention processes than our memory task are

probably more promising in showing a relationship between

CV responses and performance (e.g., Gaillard and Kramer,

2001; Gendolla and Richter, in press).

In summary, both experiments provide evidence for the

predictions of Wright’s (1996) integrative analysis that the

effects of incentive value on cardiovascular reactivity depend

on the clarity of task difficulty. If task difficulty is known to the

performer and either low or very high, incentive value does not

moderate CV reactivity. But if task difficulty is unclear, CV

responses are proportional to incentive value and independent

of objective task difficulty.

Acknowledgement

We would like to thank Anja Eichmann, Alexandra Russell,

and Annick Tinembart for their help by serving as experi-

menters, and Kerstin Brinkmann for helpful comments on an

early draft of the manuscript.

References

Al’Absi, M., Bongard, S., Buchanan, T., Pincomb, G.A., Licino, J., Lovallo,

W.R., 1997. Cardiovascular and neuroendocrine adjustment to public

speaking and mental arithmetic stressors. Psychophysiology 34, 266–275.

Belanger, D., Feldman, S.M., 1962. Effects of water deprivation upon heart rate

and instrumental activity in the rat. J. Comp. Physiol. Psychol. 55, 220–225.

Benjamin, L., 1967. Facts and artifacts in using analysis of covariance to

‘‘undo’’ the law of initial values. Psychophysiology 4, 187–206.

Berne, R.M., Levy, M.N., 1977. Cardiovascular Physiology, 3rd edn. C.V.

Mosby, St. Louis.

Bongard, S., 1995. Mental effort during active and passive coping: a dual task

analysis. Psychophysiology 32, 242–248.

Bongard, S., Hodapp, V., 1997. Active coping, work-pace, and cardiovascular

responses: evidence from laboratory studies. J. Psychophysiol. 11, 227–237.

Brehm, J.W., Self, E.A., 1989. The intensity of motivation. Annu. Rev.

Psychol. 40, 109–131.

Brownley, K.A., Hurwitz, B.E., Schneiderman, N., 2000. Cardiovascular

psychophysiology. In: Cacioppo, J.T., Tassinary, L.G., Berntson, G.G.

(Eds.), Handbook of Psychophysiology. Cambridge University Press, New

York, pp. 224–262.

Elliot, R., 1969. Tonic heart rate: experiment on the effects of collative

variables lead to a hypothesis about its motivational significance. J. Pers.

Soc. Psychol. 12, 211–228.

Fowles, D.C., Fisher, A.E., Tranel, D.T., 1982. The heart beats to reward: the

effect of monetary incentive on heart rate. Psychophysiology 19, 506–513.

Gaillard, A.W.K., Kramer, A.F., 2001. Theoretical and methodological issues in

psychophysiological research. In: Backs, R.W., Boucsein, W. (Eds.),

Engineering Psychophysiology. Erlbaum, Mahwah, NJ, pp. 31–58.

Gellatly, I.R., Meyer, J.P., 1992. The effects of goal difficulty on

phsyiological arousal, cognition, and task performance. J. Appl. Psychol.

77, 694–704.

Gendolla, G.H.E., 1998. Effort as assessed by motivational arousal in identity

relevant tasks. Basic Appl. Soc. Psychol. 20, 111–121.

Gendolla, G.H.E., 1999. Self-relevance of performance, task difficulty, and

task engagement assessed as cardiovascular response. Motiv. Emot. 23,

45–66.

Gendolla, G.H.E., Krusken, J., 2001a. The joint impact of mood state and task

difficulty on cardiovascular and electrodermal reactivity in active coping.

Psychophysiology 38, 539–548.

Gendolla, G.H.E., Krusken, J., 2001b. Mood state and cardiovascular response

in active coping with an affect-regulative challenge. Int. J. Psychophysiol.

41, 169–180.

Gendolla, G.H.E., Krusken, J., 2002a. Informational mood impact on effort

related cardiovascular response: the diagnostic value of moods counts.

Emotion 2, 251–262.

Gendolla, G.H.E., Krusken, J., 2002b. The joint effect of informational mood

impact and performance-contingent incentive on effort-related cardiovas-

cular response. J. Pers. Soc. Psychol. 83, 271–285.

Gendolla, G.H.E., Krusken, J., 2002c. Mood state, task demand, and effort-

related cardiovascular response. Cogn. Emot. 16, 577–603.


Gendolla, G.H.E., Richter, M., in press. Ego-involvement and mental effort:

cardiovascular, electrodermal, and performance effects. Psychophysiology.

Gendolla, G.H.E., Abele, A.E., Krusken, J., 2001. The informational impact of

mood on effort mobilization: a study of cardiovascular and electrodermal

responses. Emotion 1, 12–14.

Gerin, W., Litt, M.D., Deich, J., Pickering, T.G., 1995. Self-efficacy as a

moderator of perceived control effects on cardiovascular reactivity: is

enhanced control always beneficial. Psychosom. Med. 57, 390–397.

Hahn, W.W., Stern, J.A., McDonald, D.G., 1962. Effects of water depreciation

and bar pressing activity on heart rate in the male albino rat. J. Comp.

Physiol. Psychol. 55, 786–790.

Levick, J.R., 2003. An Introduction to Cardiovascular Physiology, 4th edn.

Oxford University Press, New York.

Light, K.C., 1981. Cardiovascular responses to effortful active coping:

implications for the role of stress in hypertension development. Psycho-

physiology 18, 216–225.

Llabre, M.M., Spitzer, S.B., Saab, P.G., Ironson, G.H., Schneiderman, N., 1991.

The reliability and specificity of delta versus residualized change as

measure of cardiovascular reactivity to behavioral challenges. Psychophys-

iology 28, 701–711.

Locke, E.A., Latham, G.P., 1990. A Theory of Goal Setting and Performance.

Prentice Hall, Englewood Cliffs, NJ.

Lovallo, W.R., Wilson, M.F., Pincomb, G.A., Edwards, G.L., Tompkins,

P., Brackett, D.J., 1985. Activation patterns to aversive stimulation in

man: passive exposure versus effort to control. Psychophysiology 22,

283–291.

Obrist, P.A., 1976. The cardiovascular–behavioral interaction as it appears

today. Psychophysiology 13, 95–107.

Obrist, P.A., 1981. Cardiovascular Psychophysiology: A Perspective. Plenum,

New York.

Papillo, J.F., Shapiro, D., 1990. The cardiovascular system. In: Cacioppo,

J.T., Tassinary, L.G. (Eds.), Principles of Psychophysiology: Psychical,

Social, and Inferential Elements. Cambridge University Press, New York,

pp. 456–512.

Richter, M., Gendolla, G.H.E., Krusken, J., in press. Context-dependent mood

effects on mental effort mobilization: a view from the mood-behavior-

model. In: Columbus, F. (Ed.), The Psychology of Moods, Nova Science

Publishers, Hauppauge, NY.

Rosenthal, R., Rosnow, R.L., 1985. Contrast Analysis. Cambridge University

Press, New York.

Schwerdtfeger, A., 2004. Predicting autonomic reactivity to public speaking:

don’t get fixed on self-report data!. Int. J. Psychophysiol. 52, 217–224.

Sherwood, A., Dolan, C.A., Light, K.C., 1990. Hemodynamics of blood

pressure responses during active and passive coping. Psychophysiology 27,

656–668.

Sigall, H., Mills, J., 1998. Measures of independent variables and mediators are

useful in social psychology experiments: but are they necessary? Pers. Soc.

Psychol. Rev. 2, 218–226.

Smith, T.W., Baldwin, M., Christensen, A.J., 1990. Interpersonal influence as

active coping: effects of task difficulty on cardiovascular reactivity.


Smith, T.W., Nealey, J.B., Kircher, J.C., Limon, J.P., 1997. Social determinants

of cardiovascular reactivity: effects of incentive to exert influence and

evaluative threat. Psychophysiology 34, 65–73.

Smith, T.W., Ruiz, J.M., Uchino, B.N., 2000. Vigilance, active coping, and

cardiovascular reactivity during social interaction in young men. Health

Psychol. 19, 382–392.

Storey, P.L., Wright, R.A., Williams, B.J., 1996. Need as a moderator of the

difficulty–cardiovascular response relation: the case of fluid deprivation.

J. Psychophysiol. 10, 228–238.

Tranel, D.T., Fisher, A.E., Fowles, D.C., 1982. Magnitude of incentive effects

on heart rate. Psychophysiology 19, 514–519.

Wilson, T.D., Dunn, E.W., 2004. Self-knowledge: its limits, value, and potential

for improvement. Annu. Rev. Psychol. 55, 493–518.

Wright, R.A., 1996. Brehm’s theory of motivation as a model of effort and

cardiovascular response. In: Gollwitzer, P.M., Bargh, J.A. (Eds.), The

Psychology of Action: Linking Cognition and Motivation to Behaviour.

Guilford, New York, pp. 424–453.

Wright, R.A., 1998. Ability perception and cardiovascular response to

behavioral challenge. In: Kofta, M., Weary, G., Sedek, G. (Eds.), Control

in Action: Cognitive and Motivational Mechanisms. Plenum, New York,

pp. 197–232.

Wright, R.A., Brehm, J.W., 1989. Energization and goal attractiveness. In:

Pervin, L.A. (Ed.), Goal Concepts in Personality and Social Psychology.

Erlbaum, Hillsdale, pp. 169–210.

Wright, R.A., Dill, J.C., 1993. Blood pressure responses and incentive

appraisals as a function of perceived ability and objective task demand.


Wright, R.A., Kirby, L.D., 2001. Effort determination of cardiovascular

response: an integrative analysis with applications in social psychology.

Adv. Exp. Soc. Psychol. 33, 255–307.

Wright, R.A., Tunstall, A.M., Williams, B.J., Goodwin, J.S., Harmon-Jones, E.,

1995. Social evaluation and cardiovascular response: an active coping

approach. J. Pers. Soc. Psychol. 69, 530–543.

Wright, R.A., Killebrew, K., Pimpalapure, D., 2002. Cardiovascular incentive

effects where a challenge is unfixed: demonstrations involving social

evaluation, evaluator status, and monetary reward. Psychophysiology 39,

188–197.

incentive effects on cardiovascular reactivity in active coping with unclear task difficulty

Documents