1. as a central state is what causes

1. being caused by particular patterns of threat-related stimuli,2. categories such as ‘fear’ and ‘disgust’ correspond to functional categories that evolution has sculpted3. This is also the reason why it would be nonsensical to assign ‘fear’ (or any other emotion) to an alien species from another planet (unless we knew a lot about its environment and the mechanisms for evolution on that planet, and these were sufficiently similar to the case on earth).4. At the outset, we need an operational definition of ‘fear’. The approach I advocate is pragmatic: fear is an intervening variable between sets of context-dependent stimuli and suites of behavioral response5. It is not identified with the conscious feeling of being afraid, nor with fear behaviors such as screaming and running away.6. Instead, fear as a central state is what causes the conscious experience (in some species and under some conditions) and what causes the fear behaviors7. Fear in turn is caused by particular sets of stimuli (in a context-dependent way). Fear is what links sets of stimuli to patterns of behaviors. Unlike with reflexes, this link in the case of an emotion like fear is much more flexible (hence all the parenthetical qualifiers in this paragraph) and the state can exist for some time after the eliciting stimuli8. What is fear? The state evoked by threat. What is threat? That which causes fear. The reason that our definition of fear is not circular is that it is anchored not only in stimuli, but also in behaviors. Certain sets of stimuli and behaviors covary; if they did not, we would never be able to attribute fear to other people or animals, but we can.9. As with moods in general, there is substantial heritability for trait anxiety, and for anxiety disorders, although it seems clear that most of the genetic variance is accounted for by complex polygenic interactions with environmental stressors, rather than by any single gene10. The decoupling between an immediate stimulus trigger and a fear state also makes trait anxiety prone to dysregulation: anxiety disorders constitute one of the most common psychiatric illnesses (all in all, close to 20% of the population suffers from an anxiety disorder of some kind in any given year 136).11. There are clinical distinctions between dysfunctions of fear processing that have some evidence for involvement of specific brain structures and neurotransmitter systems, making them candidates for functional subtypes of fear that will be reflected in the brain.12. Generalized anxiety disorder features chronic worry about a range of events, typically focused on the future. Panic disorder, on the other hand, results from a severe and acute fear response — often in the absence of an ability to cope, such as the sensation of suffocation that can be experimentally induced by inhaling carbon dioxide 13. Phobias are characterized both by predictive anxiety as well as acute flight responses, often to specific classes of stimuli14. fear-inducing stimuli, and access to fear-related thoughts and memories15. There are alternative possibilities for how pathology might emerge from fear, not mutually exclusive with the above: it simply might represent an exaggerated fear reaction.16. Thus, increased expectation of, and rumination about fear, can be associated with increased vigilance and attention to potentially dangerous stimuli17. The consequence is a generally heightened state of arousal, accompanied by many fear-like responses that can be thought of as false positives from a signal detection perspective. The threshold for detecting fear has simply been set too low and too many stimuli that have a very low probability of being dangerous are misinterpreted as dangerous18. There is yet another view regarding pathological states of fear: that they arise from the operation of a module that is relatively impenetrable to control, operates relatively automatically, and has been tuned by evolution. All these features could render such a module not only difficult to override, but also responsive to stimuli in a way that would have been adaptive in our ancestral environment but may no longer be so