Which of the following situations describes an approach-avoidance conflict?

4 From Basics to States and Traits: Assessing Approach, Avoidance, and Goal Conflict

Our analysis of the basics of approach, avoidance, and goal conflict shows that care must be exercised when using complex combinations of motivational stimuli and complex paradigms. Variations in valuation, such as loss aversion, differential effects of approach and avoidance gradients, direct interactions between approach and avoidance systems, and the asymmetric impact of goal conflict on avoidance relative to approach, must all be taken into account when interpreting many of the paradigms currently used. However, in principle, state analysis of these systems is straightforward.

One simplifying step is to use money as the source of motivation. Organizations that find work for students and other casual workers can supply participants with a hunger for money sufficient to make them willing to work for the local minimum wage. Importantly, loss of money from an existing store can then be used as a motivator, with the knowledge that its external value is the same as the gain of the same amount of money used as a positive motivator. As shown in Figure 3, gain and loss can be presented or omitted to generate approach or avoidance. The amounts of gain and loss can then be varied parametrically to allow mathematical extraction, separately, of the contribution of gain/loss sensitivity differences and of approach/avoidance sensitivity differences. Using these methods, loss aversion and approach preference have been demonstrated.188

For neuroimaging, it is also important to use designs that allow the calculation of appropriate contrasts. If one wishes to image goal conflict activation, one must accept that gain, loss, approach, avoidance, and other systems will all necessarily be activated when approach-avoidance conflict is being generated. To deal with this requires the use of at least three conditions. For example, with conditions that deliver two alternatives with a 50% probability on any trial, one could have: (1) net gain (−10c, +20c); (2) conflict (−15c, +15c); and (3) net loss (−20c, +10c). A contrast of neuroimaging activation in condition 2 against the average of condition 1 and condition 3 would assess goal conflict-specific activation while eliminating the effects of external value (15c = (10c+20c)/2) and controlling for effects of factors such as risk. In practice, because of loss aversion, to statistically eliminate the effects of gain, loss, approach, and avoidance, when assessing conflict, one would need the ratio of gain/loss amounts tailored to each individual’s degree of loss aversion. Additional conditions would allow the separation of the effects of gain from the effects of loss and effects of approach from the effects of avoidance.188

For those interested in goal gradients (Figures 2 and 4), existing virtual reality maze paradigms (see Section 2.2) or even simpler runway analogues could be used. These have already demonstrated effects related to distance from a “predator,” as well as differences between simple anticipation of shock and the response to actual shock delivery. Combined with the presentation of money (to selected money-hungry participants), these virtual reality paradigms allow manipulation of the full gamut of parameters that have previously been used in animal behavior tests.

It is tempting, in the imaging of personality, to select questionnaires that have been designed, in theory, to tap into specific neurobiological functions (e.g., scales purporting to measure Gray’s Behavioral Inhibition System) but that have not in fact been neurobiologically validated. However, as we noted earlier, the nascent neuroscience of personality should not assume the very hypotheses that need to be tested. Psychologists’ presuppositions about which neural systems are responsible for any given trait, as measured by a questionnaire, may well be wrong. With approach, avoidance, and conflict, we are dealing with primordial biological systems whose elements have evolved to fulfill system-specific purposes. The state activation of these systems can be, and has been, assessed directly, with specific components extractable through appropriate contrasts. These specific components of neural state activation provide, we would argue, the best basis both for assessing personality-related variation in activation and for deriving questionnaire scales or other measures of approach, avoidance, and goal conflict traits, using the criterion approach described in Section 3. How the sensitivities of the approach, avoidance, behavioral inhibition, and other neural systems give rise to variation in traits is the key question that the field must strive to solve. A genuinely neuroscientific approach will provide a solid basis for future attempts to understand the contribution of these fundamental neural systems to traits such as extraversion, neuroticism, impulsivity, and others.

VIII Serotonin signaling modulates distinct processes contributing to the expression of anxiety- and fear-related defensive behavioral responses in a target-specific manner

Serotonin signaling in the BNST moderates approach/avoidance behavior. For example, optogenetic activation of serotonergic terminals in the dlBNST increases center time in the OFT and open-arm entries in the EPM, without affecting locomotion, in a 5-HT1A heteroreceptor–dependent manner (Garcia-Garcia et al., 2017). Conversely, optogenetic activation of serotonergic terminals in the BNST increases open-arm avoidance in the EPM and increases feeding latency in the novelty-suppressed feeding (NSF) test in a 5-HT2C receptor–dependent manner (Marcinkiewcz et al., 2016). Interestingly, activation of this aversive serotonergic circuit in the fear-potentiated startle test did not affect acquisition, but enhanced recall to both cue and context (Marcinkiewcz et al., 2016), suggesting that serotonin in the BNST enhances learned, but not innate, freezing behavior. Together, this evidence suggests that serotonergic signaling in the BNST can promote or inhibit the expression of anxiety- and fear-related defensive behavioral responses in a serotonin receptor subtype-dependent manner.

Serotonergic signaling in the BLA enhances aversive memory acquisition. Exposure to inescapable stress, but not exposure to escapable stress, enhances serotonin release in the BLA during the juvenile social exploration test of anxiety and facilitates social avoidance in a 5-HT2C receptor–dependent manner (Christianson et al., 2010). In animals without prior stress exposure, agonism of 5-HT2C receptors in the BLA enhances shock-induced freezing without affecting avoidance learning (Strong et al., 2011), suggesting 5-HT2C receptors in the BLA enhance aversiveness. Moreover, upregulation of 5-HT2C receptors in the BLA by chronic immobilization stress enhances long-term memory formation, as measured by cue-induced freezing 24 h postacquisition (Baratta et al., 2016). Interestingly, this effect is blocked by BLA 5-HT2C receptor antagonism immediately following acquisition, and by photoinhibition of the BLA-projecting serotonergic neurons during acquisition (Baratta et al., 2016). Together, these data suggest that 5-HT2C receptor activation in the BLA during exposure to aversive stimuli mediates associations to negative outcomes, while activation of these receptors poststimulus enhances aversive memory formation, contributing to the development of an avoidant phenotype.

Serotonergic signaling in the NAcb promotes sociability. CSDS results in an adaptive increase of social avoidance, and results in decreased excitability in serotonergic neurons in the DRD/DRV (Challis et al., 2013). Moreover, optogenetic inhibition of DRV GABAergic neurons during postdefeat sensory contact results in a resilient phenotype (Challis et al., 2013), while photoactivation of glutamatergic vmPFC terminals in the DR promotes a susceptible phenotype, through DR GABAergic neuron activation (Challis et al., 2014). Interestingly, photostimulation of serotonergic terminals in the NAcb promotes sociability in the juvenile social exploration test in a 5-HT1B receptor-dependent manner (Walsh et al., 2018). This may suggest that mPFC-mediated decreases in DRD/DRV serotonergic signaling following social defeat promotes increased anxiety-related behavior, potentially through downregulation and/or reduced activation of 5-HT1B receptors in the NAcb. It is interesting that the CSDS paradigm promotes social avoidance by decreasing serotonergic signaling (Challis et al., 2013), whereas uncontrollable stress promotes social avoidance by increasing serotonergic activity (Christianson et al., 2010). These data suggest that a socially avoidant phenotype can be induced by decreases in appetitive signaling or by increases in aversive signaling arising from serotonergic DR neurons, and that social approach behavior is mediated by serotonergic signaling in the NAcb.

Serotonergic signaling in the dPAG promotes behavioral inhibition. Pharmacological activation of the DR reliably increases escape latency and increases latency to enter the open-arm of the ETM (Pobbe & Zangrossi, 2005; Sena et al., 2003). These effects are reversed by inhibition or selective lesion of serotonergic DR neurons (Pobbe & Zangrossi, 2005; Sena et al., 2003), and by intra-dPAG administration of a selective 5-HT2A/C receptor antagonist (Pobbe & Zangrossi, 2010). Moreover, these apparent anxiogenic/panicolytic effects are mimicked by chemical stimulation of the LHb (Pobbe & Zangrossi, 2008) in a dPAG 5-HT2A/C receptor-dependent manner (Pobbe & Zangrossi, 2010). This suggests that the effect of serotonergic signaling in the dPAG on avoidance/escape behavior is moderated, at least in part, by aversive signals from the LHb. However, this fails to explain the apparent panicolytic effects of activating the LHb-DR-dPAG circuit. An alternative explanation is that, in the absence of reward/punishment-predicting cues, serotonin signaling in the dPAG decreases effort output, i.e., it is not worth the energy cost to either approach or avoid. Therefore, removing the “no-reward” signal from the LHb to the DR, or blocking 5-HT2A/C receptors in the dPAG, increases effort in the absence of clear appetitive or aversive cues. This hypothesis is further supported by research showing that optogenetic activation of glutamatergic mPFC axon terminals in the LHb strongly increases immobility in the FST (Warden et al., 2012). While this can be interpreted as an increase in depressive-like behavior, it can equally be interpreted as the adaptive conservation of energy (Molendijk & de Kloet, 2015) in the presence of “no-reward”signals from the LHb to the DR. Furthermore, optogenetic activation of the DR serotonergic neurons promotes waiting for a food reward rather than exploring alternatives, an effect strongest when the probability of reward is high but timing of delivery is uncertain (Miyazaki et al., 2018), further implicating the serotonergic DRVL in promoting behavioral inhibition. This idea suggests that DRVL serotonergic neurons may be one important component of Gray's proposed behavioral inhibition system (Gray & McNaughton, 2000). While speculative, serotonergic DR-dPAG signaling may moderate adaptive approach/avoidance behavior in a cost/benefit-dependent manner by conserving energy when the probability of rewarding outcomes is low and promoting waiting when the probability is high.

Serotonin signaling in the PFC moderates impulsivity and behavioral adaptation. Serotonin signaling in the PFC bidirectionally modifies neural activity and output of this region (for review, see Puig & Gulledge, 2011). In the common marmoset, selective lesion of serotonergic terminals in the PFC (Clarke et al., 2004, 2005; Rygula et al., 2015) substantially impairs reversal learning. In zebrafish, selective lesion of cortical serotonergic terminals impairs adaptive avoidance learning to shock-predicting cues without affecting unconditioned freezing (Amo et al., 2014). In rats, 5-HT1A receptor agonists administered to the mPFC reduce impulsivity (Carli, Baviera, Invernizzi, & Balducci, 2006). This evidence suggests that PFC serotonin signaling contributes to behavioral adaptation in both rewarding and aversive contexts.

Serotonin signaling in the LHb moderates appetitive and aversive states. Serotonin signaling can potentiate, as well as inhibit, output from the LHb (for review, see Tchenio, Valentinova, & Mameli, 2016). In vitro electrophysiology evidence shows that activation of 5-HT2/3 receptors potentiates glutamatergic transmission from the LHb (Xie et al., 2016; Zuo et al., 2016), while activation of 5-HT1B receptors inhibits presynaptic glutamatergic inputs to this region (Hwang & Chung, 2014). Furthermore, photoactivation of excitatory entopeduncular nucleus terminals in the LHb in vivo promotes place aversion, while bath application of serotonin in vitro inhibits photoactivation of these terminals (Shabel et al., 2012). Rats exposed to chronic unpredictable mild stress show a decrease in sucrose preference and increased immobility in the FST (Zhang et al., 2018). In these rats, photoactivation of serotonergic DR afferents in the LHb reinstates normal levels of sucrose preference and FST mobility through actions on 5-HT1B receptors (Zhang et al., 2018). Finally, intra-LHb administration of the 5-HT2C receptor agonist, Ro60-0175, reduces sucrose preference and increases immobility in the FST (Han et al., 2015). While more research is needed in order to understand the behavioral effects of serotonergic signaling in the LHb, these data suggest that activation of 5-HT2C receptors in the LHb promotes passive coping and anhedonia. Meanwhile, 5-HT1B receptor activation has the opposite effect, consistent with the hypothesis that serotonin exerts opposed control over appetitive and aversive states.

1.07.3.1.2 Approach–Avoidance Tendencies and Addiction

As mentioned above, the usually helpful automatic approach–avoidance tendencies can be biased in psychopathology, in ways that are hard to control or modify (see Loijen et al., 2020). Assessment studies have shown that in many cases, the automatic tendencies coincide with more controlled, conscious avoidance behavior. Spider phobics, for instance, not only consciously decide to avoid areas that may contain spiders, they also show automatic avoidance of spiders in joystick tasks (Rinck and Becker, 2007) and virtual environments (Rinck et al., 2010). In some cases, however, there is a discrepancy between self-report and controlled behavior on the one hand, and automatic tendencies on the other. Socially anxious individuals, for instance, evaluated smiling faces as positive, but avoided them nevertheless (Heuer et al., 2007). Another example involves dysfunctional approach tendencies (rather than avoidance tendencies), which seem to prevail in addictions (see Loijen et al., 2020). In alcohol addiction, these tendencies have been studied intensively, and this particular case is another example of EP research that evolved all the way from early assessment to clinical application.

Early assessment studies of approach–avoidance tendencies revealed an alcohol-approach tendency in heavy-drinking students, possibly related to genetic vulnerability factors (Wiers et al., 2009). Based on this finding, in an early joystick-based induction study (Wiers et al., 2010), students were randomly assigned to a training that involved approaching pictures of alcoholic beverages and avoiding pictures of non-alcoholic beverages, or to the reversed training. Consistent with the EP focus on behavioral measures other than self-report, the effect of the short 1-session training was assessed with a so-called “taste test” that followed the joystick task. Participants were asked to select their favorite beer from three neutral glasses. Unknown to the participants, all glasses contained the same beer, and researchers did not care about the choice. Instead, they were interested in the amount of beer consumed during the test. Interestingly, the group trained to approach alcohol drank about one glass more than the group trained to avoid alcohol, suggesting a causal influence of the training on consumption. This study also illustrates a frequent shortcoming of induction studies: Since there was no control condition without training, we cannot know whether the approach-alcohol training increased consumption, whether the avoid-alcohol training decreased it, or whether both was the case (the same applies to the classical ABM induction study by MacLeod et al., 2002).

The demonstration of a causal relation between alcohol-approach tendencies and consumption paved the way for corresponding modification studies, and these yielded surprising results. In a series of large-scale studies conducted in a German rehabilitation clinic for abstinent alcohol-dependent patients, it was repeatedly shown that compared to no training or sham training, a multi-session alcohol-avoidance training reduced relapse rates at 1-year follow-up by about 8%–10% (Wiers et al., 2011; Eberl et al., 2013; Rinck et al., 2018). Independently, Australian studies also reported a relapse-preventive effect of this training (Manning et al., 2016, 2021). Moreover, fMRI studies were conducted to identify the neural correlates of the alcohol-avoidance training (Wiers et al., 2015). As a result of this positive empirical evidence, the training was recently added to the German guidelines for the treatment of alcohol addiction. It should be noted, however, that it remains to be tested how beneficial such a training can be for individuals other than currently abstinent inpatients (outpatients, heavy drinkers), for other treatment goals (reduced consumption), or for other drugs (nicotine, cannabis).

C Mobbing Calls

Mobbing calls are emitted mainly by conflicting tendencies of approach-avoidance of potential predators. They function to alarm other animals and to provide information as to the location of the enemy. When mobbing, all animals leap toward the predator, then withdraw from it. This behavior is accompanied by staring at the enemy. They show defensive threat signals such as arch-postures, piloerection, and swaying from side to side. The mobbing response can be initiated by a wide variety of objects, situations, and individuals (Bakker et al., 2014; Epple, 1968). The calls show a wide frequency spectrum, strong frequency modulations, and frequent repetition.

Epple (1968) showed that tsik calls are produced by common marmosets, Mico a. argentatus and L. rosalia, when mobbing a potential predator (high arousal). The mobbing calls were very contagious: they alarm the whole group and cause increased alertness in all animals. When marmosets hear a group member calling, even if they do not see it, or when tape recordings of the vocalizations are played to them, they usually start the mobbing calls. Even calls of species from a different genus will initiate the response.

Tsik calls are also given during hostile encounters with other marmosets, but under these circumstances, only a few calls are uttered rather than the long series of calls that occurs in mobbing. The tsik calls, which function as urgent contact calls in common marmoset newborns, change their social significance with age. After the third week of life, when the babies become more independent, they may approach a potential predator. Under such circumstances, if adults are present, they immediately start mobbing the subject whether the intruder is animal or human. The mobbing calls alarm the young ones as well, and they retreat from the enemy and join in the mobbing. It seems likely that the infants learn what to fear from the behavior of the adult group members. With increasing age, infants utter tsik calls almost exclusively when alarmed by the presence of a potential predator.

In common marmosets, the tsik calls have a tonal structure. They show a wide frequency spectrum and much frequency modulation, more apparent in the harmonics than in the fundamentals. The call durations are 0.05–0.09 s and the harmonics reach up to 80 kHz. In Mico a. argentatus, the physical structure and duration of the tsik calls are similar to those of common marmosets while the form of the harmonics is quite different. The tsik calls of L. rosalia, when mobbing a potential predator, are similar in acoustic character, physical structure, and duration to the mobbing calls of the other species, but show a different frequency modulation. The sound frequencies reach up to 80 kHz. For all species that are in the state of very high arousal, 2–10 tsik calls may follow each other so closely that the human ear perceives them as a single sound.

Epple (1968) described in O. spixi long series of tsik calls occasionally intermingled with trills; they were given when mobbing a predator. The tsik calls have duration of 0.05–0.17 s and are longer in the genus Oedipomidas than in any of the other species described here. With increasing arousal, the calls become longer and the harmonics show less frequency modulation. The calls have a frequency spectrum from 2 kHz to at least 60 kHz. No measurements were performed to detect frequencies above this level.

Overview of Treatment

The treatment’s main objectives are to help the patient recognize his worries as approach-avoidance behavior, discriminate between different types of worries, and apply the correct strategy to each type. Our intervention progresses over approximately 18 1-h sessions and involves four components: (1) presentation of treatment rationale, (2) behavioral analysis and awareness training, (3) specific worry interventions, and (4) reevaluation of worry appraisal. Although it always involves these four components, the treatment program is tailored to the individual needs of each patient. For instance, for patients who report worrying mostly about problems which are grounded in reality, adapted PST with emphasis on problem orientation would be the principal specific worry intervention. For patients who worry mostly about highly remote events, functional cognitive exposure would be the main specific worry intervention.

Treatment typically lasts 4 months with follow-up sessions over a one-year period. Ideally, the first eight sessions are conducted on a biweekly basis in order to closely monitor the patient’s initial progress. Then, eight weekly sessions are followed by two fade-out sessions (usually two to four weeks apart). We also recommend three follow-up sessions over a one-year period, at three, six and 12 months. Although sessions typically last 1 h, those that involve exposure practice may last up to 1.5 h.

Which of the following describes an approach

What is approach

Which of the following is an avoidance

What is an approach