The term ‘radical’ (when applied in the social sphere) has two meanings that at first glance appear distinct from each other. One meaning pertains to the word’s usage as a noun: A radical is a nonconformist, a troublemaker, a deviationist. The second meaning pertains to the term’s use as an adjective. Here, radical means thorough, fundamental, or essential. This latter usage derives from the Latin word ‘radix’ or ‘root’ in that a root underlies the plant and is essential to its existence.

But what does this have to do with deviancy and nonconformity? On the surface of it, rather little – and the term’s use in this fashion may appear enigmatic. Yet, there could be more here than meets the eye. Indeed, looking deeper into the psychology of the radical (as a noun), we find a kind of essentialism, or purism; a single mindedness, or as Soren Kierkegaard (1886/1938) felicitously put it, “the willing of one thing,” which in turn recalls the term’s adjective application.

‘Radicals’ are often referred to as ‘extremists.’ But what is extremism? Again, two senses of the term are apparent. One sense is statistical and refers to ends (i.e., extremes) of the distribution. Extremists are rare, they are unusual or infrequent within an aggregate, and their activities are not what most people do. The other sense of extremism relates to intensity, or magnitude. To refer to something as ‘extreme’ is to depict it as intense, powerful, or considerable (as in extreme hunger or thirst, or extreme disappointment). As can be seen then, radicalism and extremism have important parallels that explain their interchangeable use: (1) they both denote something that is rare and infrequent, and (2) they both connote something that has special poignancy by dint of its magnitude or essentiality.

But beyond hermeneutics, the question is whether ‘extremism’ and/or ‘radicalism’ have a psychological reality, versus representing mere ways of speaking devoid of a deeper psychological basis. I believe that the former is, indeed, the case and that extremism defines an authentic psychological state. A major implication of this notion is that many different ‘extremisms’ (e.g., violent extremism, extreme diets, extreme sports or extreme addictions) share a psychological dynamic in common, and differ in the contents or dimension, namely that which the term ‘extreme’ qualifies.

I define motivational balance as a state in which all the basic needs constitute active concerns whose fulfillment drives individuals’ behavior. These needs constrain one another such that behavior that gratifies only some needs while undermining others tends to be avoided. For instance, one’s hunger may co-exist with concerns about health, and taste; as a consequence, foods that are unhealthy or foul-tasting would be avoided. One’s need for intimacy and relatedness may temper one’s need for achievement, thus promoting a work-family balance, etc.

At times, however, a motivational imbalance may occur wherein a given need receives disproportionate emphasis, overriding the others. This state may be described as one of prepossession, in which one’s mind is predominantly absorbed with a given motivational concern, and is oblivious to all else (Shah, Friedman, & Kruglanski, 2002). For instance, under extreme hunger one might be ready to eat anything at all, regardless of its healthfulness, and a highly ambitious person, driven by an unstoppable drive to succeed, may become a workaholic and sacrifice her or his personal relations, health, even autonomy, on the altar of work. Thus, where a given need becomes particularly intense, alternative needs recede in salience, liberating possible behavior from their constraints. In consequence, the set of behavioral options for gratifying the dominant need expands, through inclusion of formerly prohibited behaviors detrimental to the now inhibited needs. For instance, when one’s (acquired) need for a given intoxicating substance (e.g., alcohol, crack, heroin) is particularly intense, it may prompt behaviors destructive to self and others (e.g., foregoing healthy nutrition, neglecting one’s work obligations, engaging in criminal behavior) whose sole purpose is to obtain the object of one’s desire by any means necessary. Such behaviors merit the epithet extreme because they denote a deviation from a motivational balance. And because people in general strive to maintain balance, extreme behavior is infrequent, as discussed earlier.

The constraints on behavior imposed in a motivationally balanced state, and their disinhibition under motivational imbalance, were investigated by Köpetz, Faber, Fishbach, and Kruglanski (2011). One of their studies (Study 3) examined the foods that students, who had equal concerns for eating enjoyment and weight control, were contemplating for lunch. In one experimental group, commitment to the goal of food enjoyment was augmented through the technique of mental contrasting (of subjective values of given states of affairs, and barriers to attaining them; Oettingen, 2000; Oettingen, Pak, & Schnetter, 2001). It was found that as compared to a control condition where the eating enjoyment and weight control goals were in balance, participants whose commitment to food enjoyment was enhanced listed more foods (reflecting an expansion of the number of means to the dominant goal under motivational imbalance). Of interest, too, the additional foods listed were rated higher on taste but also on caloric content (at odds with the weight control objective) whereas in the control (balanced) condition, the fewer foods listed were equal on taste but lower on caloric content. A subsequent experiment (Study 4) where commitment to the food enjoyment goal was manipulated via sequential priming obtained the same result. And a final experiment additionally showed that an increase in the number of means to the dominant goal through the listing of caloric foods was mediated by inhibition of the dieting (weight control) goal.

Arousal of one’s need for significance (e.g., through a significance loss, and/or the opportunity for a significance gain) does not prejudge how significance is attained and it does not necessarily imply a resort to violence. After all, personal significance defines a universal human need, which most people fulfill in peaceful ways. Where severe intergroup conflict is in place, however, unleashing violence against the adversary is often hailed as a particularly effective route to significance, meriting the group’s recognition of the individual as a hero or a martyr. Typically, societies pay homage to, and glorify those who are ready to make sacrifices on their behalf. For instance, military service that reflects soldiers’ readiness to risk life and limb for “king and country” has been universally regarded as a most honorable pursuit (Olsthoorn, 2005). Thus, even though violence isn’t significance-bestowing necessarily—it often is so actually and in light of the ubiquity of intergroup conflict in human history. The means-ends relation between violence on behalf of one’s group and the attainment of personal significance is spelled out in many ideological narratives, including those of non-state militant organizations of various sorts (Kruglanski, Gelfand, & Gunaratna, 2012).

An extensive body of recent research supports the intimate relation between the quest for significance and the support of violence on behalf of some sanctioned cause. For instance, open source materials about successful suicide bombers (i.e., individuals who volunteered to die while carrying out their mission) suggest that those animated by a loss of significance and/or evincing a particularly strong appetite for significance gain perpetrated more severe casualties (in terms of the numbers of people killed and/or wounded in the attacks) than individuals with a less intense quest for significance (Webber et al., 2017). Examination of ideologically motivated crimes carried out in the U.S. yielded that violent (vs. non-violent) crimes were more likely to be committed by individuals who suffered considerable loss of significance in one or more life domains (Jasko et al., 2016). Finally, Muslim immigrants in the U.S. who felt marginalized and discriminated against were more likely to support and identify with radical Islamist groups (Lyons-Padilla, Gelfand, Mirahmadi, Farooq, & van Egmond, 2015; for a review, see Kruglanski, Belanger, & Gunaratna, 2018).

The motivational imbalance at the root of extremism is enabled by basic mechanisms describable on the biological/neuronal (molecular) as well as psychological (molar) levels of analysis. The former have been investigated with animal models at different phylogenetic levels, such as mice, flies or crayfish among others. For instance, flies will tolerate a higher concentration of bitter (and potentially toxic) contaminants in food as they get hungrier. In other words, their ‘concern’ for taste seems to decline the greater their concern for nutrition becomes. Research on the brain mechanisms involved in this phenomenon reveals that taste neurons become more sensitive to sweet-tasting substances and less sensitive to bitter tastants (Inagaki, Panse, & Anderson, 2014). Similarly, research carried out with mice (Lin et al., 2011) revealed that many of the ventral hypothalamic neurons activated during male-male aggressive encounters were suppressed in the presence of females.

Activation of neurons that typically elicit aggressive behavior in the mouse affected it to a much reduced extent when the male was engaged in copulation, and it required a considerably more intense level of stimulation under these conditions to elicit attacks. This inhibition was removed following ejaculation. As Anderson (2012, p. 1085) summarized it, “This observation is consistent with…electrophysiological data suggesting that mating causes an active inhibition of attack circuitry, so that the level of artificial stimulation required to override this inhibition is increased during the consummatory phase.” These findings suggest that when mating/courtship becomes a predominant concern, other needs such as defense (e.g., against possible aggressors or invaders) are inhibited and their momentary importance to the animal diminishes.

Animals’ preference for a balanced ‘moderation’ is illustrated by a study in which an animal who is both thirsty and hungry is afforded access to two bottles of water, one of which contains a tasteless but caloric compound, and the other containing water without the nutritious compound (Elizalde & Sclafani, 1988). It is found that after drinking from each bottle, the animal will come to prefer the water with the nutritious component because it can detect the compound with receptors in its gut. In other words, the animal prefers the state in which both hunger and thirst are satisfied to a state in which only thirst is, and it does so by employing the multifinal means (Kruglanski et al., 2002) of drinking from the bottle that contains not only water but the compound as well.

In summary, animal research carried out by behavioral biologists attests both to animals’ preference for balanced states (in which their various motives, e.g., hunger and thirst, are all satisfied) and to neural mechanisms that enable the emergence of a motivational imbalance in which a given motive subjected to a particularly intense stimulation emerges as dominant alongside a parallel decline in the strength of other motives and the concomitant weakening of behavioral patterns that typically subserve them.

In lower species, the state of prepossession in which a given motive dominates others is typically of brief duration. The motivational “storm” subsides once the momentarily dominant need is taken care of and the animal is then free to turn its attention to its alternative concerns. In humans, however, the operation of cognitive and social mechanisms enables long haul persistence of prepossessive states, including an enduring engagement in violent extremism. These mechanisms are considered in what follows.

Below, I briefly describe three cognitive mechanisms that play a central role in the radicalization process. These are the processes of knowledge activation, knowledge inhibition, and construal or inference.