The aim of the present thesis was to investigate the effect of implicit fear in the process of mental effort mobilization. More specifically, the implicit-affect-primes-effort (IAPE) model (Gendolla, 2012, 2015) makes specific predictions about the impact of implicit affect on mental effort through its impact on subjective demand. The first two studies demonstrated for the first time a main effect of implicit fear on mental effort; the third and the fourth studies showed that this effect was moderated by objective task difficulty and incentive, respectively. In sum, this research provides evidence for an impact of implicit affect on mental effort as predicted by the IAPE model and its integration with motivational intensity theory (Brehm & Self, 1989) by generalizing its predictions to a so far unstudied type of implicit affect, namely implicit fear.
Mental effort has been operationalized as PEP reactivity, which represents our best indicator of beta-adrenergic activity (Kelsey, 2012). Therefore, PEP reactivity is our main measure of mental effort in the present research. However, we collected additional physiological indicators, such as blood pressure and heart rate, to control for possible preload or afterload effects which can have an influence on PEP (Sherwood et al., 1990).
3.1. PEP reactivity
The first purpose of the present research was to demonstrate the main effect of implicit fear on effort-related cardiovascular response. As predicted by the IAPE model (Gendolla, 2012, 2015) fear and sadness primes should activate the performance difficulty concept and in turn, lead to higher subjective demand and stronger PEP reactivity as long as success is possible and worthwhile. On the contrary, happiness and anger primes should activate the ease concept, which should lead to lower subjective demand and weaker PEP reactivity. Accordingly, study 1 revealed that fear primes led to stronger PEP reactivity than anger and happiness primes. As the results of study 1 showed for the first time that the effect of implicit fear effect on effort mobilization we conducted study 2 to replicate the results of study 1 and contrasted implicit fear with implicit anger and sadness. As predicted by the IAPE model, the implicit fear and sadness conditions led to stronger PEP reactivity than the implicit anger condition, successfully replicating
and extending the results of study 1. In sum, study 1 and 2 showed for the first time the predicted effect of implicit fear on effort mobilization.
Study 3 was conducted to test the moderation of the effect of fear primes on effort mobilization by objective task difficulty. The results revealed that PEP reactivity was stronger when participants were exposed to fear primes than anger primes in the easy task, because it is assumed that fear primes lead to higher subjective task demand and in turn, to higher effort.
However, in the difficult condition the strongest PEP reactivity occurred when participants were exposed to anger primes. The reason for this is that individuals exposed to fear primes should have perceived task demand as too difficult, leading to disengagement. On the contrary, individuals in the anger prime condition should set subjective demand at a high but still feasible level, leading to high effort mobilization. Thus, this study demonstrated that the effect of implicit affect on effort is moderated by objective task difficulty. This moderation replicates previous results (Silvestrini & Gendolla, 2012b; Freydefont et al., 2012) and generalizes them to implicit fear.
The next step was to investigate the role of incentive in the process of effort mobilization when participants performed a difficult task while being exposed to fear primes. In this condition disengagement was observed, which was supposed to be due to excessively high subjective demand. However, it could be that fear primes had an effect on objective rather than subjective capacity which makes it important to decipher this possibility. Therefore, we conducted a fourth study to test if the motivational deficit observed in the fear prime/difficult condition could be compensated by a high incentive. The results revealed that the weakest PEP reactivity occurred in the fear prime/low incentive condition and the strongest in the fear prime/high incentive cell.
PEP reactivity in both anger prime cells fell in between. In sum, this pattern showed that the motivational deficit observed when participants were exposed to fear primes in a difficult task could be compensated by a high incentive as previously shown for implicit sadness (Freydefont
& Gendolla, 2012). Therefore, this study suggested that implicit fear influenced effort mobilization through its impact on subjective demand rather than objective capacity as suggested by the IAPE model.
3.2. Heart rate and blood pressure reactivity
As previously mentioned, our main dependent physiological measure of mental effort is PEP reactivity (Kelsey, 2012). However, beta-adrenergic activity can also have an impact on SBP, which has also been used as an index of effort mobilization (Gendolla & Richter, 2010; Wright &
Kirby, 2001). However, SBP is also influenced by total peripheral vascular resistance (Levick, 2003), which makes it a less pure index of beta-adrenergic activity’s effect on the heart. In the present research, we found a significant effect of our manipulations on SBP only in study 4 in which the SBP reactivity pattern paralleled PEP reactivity. Indeed, study 4 revealed that high incentive led to the strongest SBP reactivity when participants were exposed to fear primes, whereas the weakest SBP response occurred when incentive was low. In the anger condition SBP reactivity fell in between. The lower reliability of SBP as an index of mental effort may account for the lack of significance observed in the three other studies.
We did not expect to find prime effects on DBP, which is even more strongly related to peripheral vascular resistance than SBP. Therefore, the absence of results on DBP in all of the studies is not odd. HR reactivity is jointly determined by the sympathetic and parasympathetic branches of the autonomous nervous system and should reflect effort mobilization only under the condition of stronger sympathetic influence (Berntson, Cacioppo, & Quigley, 1993). Similarly to DBP, no study of the present research revealed a significant effect of affect primes on HR, which can be explained by this dual autonomic innervation.
3.3. Subjective demand ratings
The IAPE model (Gendolla, 2012, 2015) posits that affect primes activate knowledge stored in long-term memory (Niedenthal, 2008) such as ease and performance difficulty concepts. An increased accessibility of concepts has an impact on judgment and behavior (Förster
& Liberman, 2007). In the context of task performance, the activation of ease and difficulty will influence the evaluation of task demand and in turn determine effort mobilization according to the principles of motivational intensity theory (Brehm & Self, 1989). More specifically, happiness and anger primes should lower task demand whereas sadness and fear primes should increase
it. Previous research successfully revealed this affect prime effect on ratings of subjective demand (Gendolla & Silvestrini, 2011; Lasauskaite et al., 2014). However, this finding has not been systematically observed in studies of our lab investigating the predictions of the IAPE model (Freydefont & Gendolla, 2012; Freydefont et al., 2012). In the present thesis, no study showed any affect prime effect on the self-report measure of subjective demand. This can be explained by the fact that judgments of task demand are made online during the accomplishment of the task but assessed retrospectively, which subjected this measure to possible biases related to memory, such as random, systematic and belief-consistent biases (Robinson & Clore, 2002).
Moreover, the influence of affect primes on the evaluation of task demand is assumed to be automatic which suggests that a more implicit measure would be more appropriate to detect this effect. Finally, regarding signal to noise ratio, subjective demand was assessed with one single item, which can cause reliability problems. For all of these reasons, the effect of affect primes on subjective demand must be strong enough to be reliably detected, which could not have happened in any of the studies in the present thesis.
3.4. Link between effort and performance
Our independent variables had a corresponding effect on effort and performance only in study 4. In the fear prime condition participants responded faster if they could win a high reward than if they could win a low reward. However, the incentive manipulation had no effect in the anger prime condition. This pattern paralleled the expected effort-related cardiovascular response which suggests a link between effort and performance. The fact that we have not systematically found this link between effort and performance in all of the studies is not odd, because effort and performance refer to different constructs. Indeed, effort is defined as the mobilization of resources to carry out instrumental behavior whereas performance is the outcome of this resource mobilization. Moreover, task performance depends at least partly on ability and strategy use rather than on effort alone, which renders the link between effort and performance complex. It is of note that the IAPE model does not make any predictions on performance measures, which makes sense according to the given differences between effort and performance just mentioned.
3.5. Conscious emotional feelings
The IAPE model posits that affect primes influence effort mobilization without eliciting conscious emotional feelings. Therefore, we measured affective states before and after exposure to affect primes to control for an impact of affective priming on conscious feelings. No study indicated that affect primes had an impact on consciously experienced affective states, in line with the mechanism posited by the IAPE model. Even though “zero effects” should always be cautiously interpreted, these data do not give support to an impact of affect primes on effort mobilization through explicit affect.
3.6. Integrative discussion
The four studies presented in the present thesis supported the predictions of the IAPE model (Gendolla, 2012, 2015) and its integration with the principles of motivational intensity theory (Brehm & Self, 1989). The focus of the present work was to test the effect of implicit fear on effort mobilization operationalized as cardiac reactivity. We demonstrated for the first time the main effect of a fear prime on effort mobilization in study 1 and replicated it in study 2. We subsequently moderated this fear prime effect by manipulating objective task difficulty and the level of incentive. By doing so, we found that implicit fear has the same effect on effort-related cardiovascular response as implicit sadness, whereas an opposite effect for implicit happiness and anger was found. This supported the predictions of the IAPE model, which posits that the impact of implicit affect on mental effort is emotion-specific rather than valence-specific. We will discuss the results found in the present thesis in light of the IAPE model and in the context of the current priming literature.
3.7. Implicit fear and subjective difficulty
The IAPE model makes specific predictions about the impact of implicit fear on effort mobilization. Accordingly, fear primes should activate knowledge about emotions (Niedenthal, 2008) and in turn influence judgments of task difficulty. The mechanism postulated by the IAPE model is that brief exposure to fear stimuli should increase the accessibility of certain relevant
information for the judgment at hand. Part of the information activated by fear prime processing is the concept of difficulty. Accordingly, this piece of information should be integrated in the judgment of task difficulty during task performance which should result in higher experienced demand and higher effort mobilization as long as success is possible and worthwhile. Previous studies conducted in our lab supported the impact of affect primes on effort mobilization complemented by the effect on self-reported subjective demand assessed at the end of the task (Gendolla & Silvestrini, 2011; Lasauskaite et al., 2014; Silvestrini & Gendolla, 2011a). However, no study in the present thesis revealed any fear prime effect on subjective demand, which is not surprising because retrospective judgment has been shown to be subjected to several biases (Robinson & Clore, 2002). Therefore, detection of the impact of implicit fear on task demand evaluation would require a more sensitive measure than self-report, which was used in the present studies. This would add more convincing support for the effect of implicit fear on mental effort through subjective demand, as predicted by the IAPE model.
3.8. Affect primes and emotional response
The IAPE model postulates that affect primes influence effort mobilization without altering conscious emotional experiences. Rather, it posits that exposure to affect primes merely activates knowledge about emotions (Niedenthal, 2008), which provides information for the judgment at hand. Corroborating this idea, none of the previous studies from our lab investigating the effect of affect primes on effort mobilization did reveal any prime impact on emotional ratings (e.g. Freydefont & Gendolla, 2012; Freydefont et al., 2012; Gendolla &
Silvestrini, 2011; Lasauskaite et al., 14; Silvestrini & Gendolla, 2011b). None of the four studies of the present thesis, found any evidence that affect primes elicited conscious affect, which is in line with the results found in previous studies investigating implicit affect and effort mobilization.
However, despite the absence of a priming effect on conscious feeling, a zero effect should always be interpreted cautiously. Indeed, the fact that we did not find any evidence suggesting a link between exposure to affect primes and emotional feeling does not permit a straightforward conclusion regarding the absence of such an effect. This is true at the conceptual level as well as at the statistical level.
Another point regarding the impact of affect primes on emotional experience is raised by authors who suggested that emotions can be experienced without awareness of their occurrence. For instance, Winkielman and Berridge (2004) used the term “unconscious emotion”, which refers to an emotional reaction that is not detected by the individual experiencing the emotion. Their arguments relied on the fact that on the one hand this affective experience is not detected by self-reported conscious emotion, but on the other hand it is strong enough to influence judgment and behavior (Winkielman et al., 2005). This idea is also suggested by Khilstrom (1999) who defined “implicit emotion” as “changes in experience, thought, or action that are attributable to one’s emotional state, independent of his or her conscious awareness of that state”. This idea is based on the fact that cognitive processes can be considered as unconscious, leading him to suggest that this could also be valid for emotional processes.
However, this is in contradiction with the traditional view of emotion, which posits that subjective experience is a critical feature of emotions (Clore, 1994; Frijda, 1999). In the present research, it is conceptually and statistically problematic to test the presence of a potential unconscious affect.
The physiological pattern observed during exposure to affect primes does not suggest the presence of any conscious emotional reaction as described in the literature on the autonomic nervous system and prototypical emotion. For instance, it has been shown that anger is characterized by an increase in diastolic and systolic blood pressure (Kreibig, 2012), which was not reflected in our anger prime conditions. Moreover, in a cognitive task participants’
experience of anger due to a provocation was associated with stronger HR and DBP responses (Bongard, Pfeiffer, Al’Absi, Hodapp, & Linnenkemper, 1997). Consequently, the results that we obtained in the anger prime conditions of the four studies can hardly be explained by a conscious feeling of anger. In sum, the cardiovascular patterns do not indicate the presence of emotional reactions, which is in line with the self-reported affective states previously discussed.
3.9. Limitations
Despite evidence supporting the implicit fear effect on effort mobilization as predicted by the IAPE model (Gendolla, 1012, 1015) and its integration with the principles of motivational
intensity theory (Brehm & self, 1989), the four studies of the present thesis raised several points that call for further investigation. First of all, the IAPE model postulates that affect primes influence effort mobilization through their impact on subjective demand. Yet, none of the presented studies revealed such an effect. Thus, a new paradigm should be developed to more reliably assess the subjective evaluation of task demand made by participants during the task.
Secondly, the affect primes used in all of the studies came from the same database (Lundqvist &
Litton, 1998), which questions if we could also successfully manipulate implicit affect with other kinds of faces. Moreover, the priming effect on effort-related cardiovascular response has also been revealed in a paradigm with implicit action and inaction words (Gendolla & Silvestrini, 2010). Therefore, changing the nature of the implicit affective stimuli could be a new way to test the predictions of the IAPE model and to generalize it to new kinds of stimuli.
In the present research, we showed that moderators, namely, task difficulty and success incentive, moderated the effect of fear primes on effort mobilization. We could try to test the moderation of the fear prime effect by other context variables such as the prime presentation time. This would allow us to test if a contrast effect can also be revealed during longer exposure to fear primes, as demonstrated for sadness and happiness (Lasauskaite Schüpbach et al., 2014).
The levels of difficulty manipulated in the four studies ranged from easy to difficult, leaving the effect of implicit fear on mental effort unknown for higher difficulty levels. Therefore, further studies could use higher objective task difficulty, such as an extremely difficult task. Given that the IAPE model posits a link between fear and difficulty, we could investigate the nature of this association. To support this proximity, a paradigm including a lexical decision task could be used to test the link between fear and difficulty, as has been demonstrated for sadness and happiness (Lasauskaite, Gendolla, Bolmont, & Freydefont, 2015). Therefore, some predictions of the IAPE model remain untested and could be addressed in further studies.
3.10. Conclusions
The present thesis has demonstrated for the first time the impact of implicit fear on effort mobilization. The four presented studies provide evidence for a main effect of fear primes, which is moderated by objective task difficulty and the presence of a success incentive. On the
one hand, these studies have further highlighted the role of fear primes in the process of effort mobilization. On the other hand, they have permitted the identification of the effect’s moderators. In sum, this thesis provides supporting evidence for the predictions of the IAPE model (Gendolla, 2012, 2015) and its integration with the principles of motivational intensity theory (Brehm & Self, 1989).