Brain heat

Updated: Feb 22

That heat and excitement are related in the mind is observable from the way we describe exciting things such as anger, violence and sex as hot in the popular expressions “hot tempered,” “don't tempt me” “temperamental,” “temper tantrum,” “hothead,” “fired up,” “furious,” “spitting fire,” “heated argument,” “hotbed,” “inflammatory,” “it’s getting hot,” “playing with fire,” “inflame the situation,” “conflagration,” “blow a fuse,” “short fuse,” “in the hot seat,” “burn in hell,” “bloody hell,” “packing heat,” “get burned,” “sick burn,” “get roasted,” “burning with rage,” “between two fires,” “burning desire,” “tempting,” “temptation,” “the heat of the moment,” “making sparks,” “have the hots for,” “in heat,” “hot stuff,” “torrid romance,” “red-hot mama,” “hot tomato,” “a hot date,” “a flame,” and, perhaps, “putting off vibes.” “Emit smoke from seven orifices” is a Chinese idiom, similar to “steam coming out of the ears” in English, meaning to be extremely angry.

Other high-temperature expressions of excitement include “five-alarm fire,” “fire-breather,” “baptism of fire,” “drop it like a hot potato,” “hot damn,” “hot digity dog,” “shocking,” “shockwaves,” and “the heat is on.” Some of these refer to fluids and fluidity, as in flames, water, steam, spit, blood and smoke, in addition to heat, with the fluidity making the expressions more exciting.

Lower temperature, lesser excitement, and lack of interaction being related in the mind is apparent in the origin and popularity of expressions such as “chill out,” “take a chill pill,” “cold-hearted,” “stone cold,” “simmer down,” “freeze people out” and “frigid.” Some of the expressions refer to solidness, inwardness and downwardness, which, like coldness, we’re tempted to mention when they don’t apply. Moderate social interactions are accordingly assigned a moderate temperature as in “even-tempered,” “warmhearted,” “warming up to,” “a warm welcome,” and “a thaw in relations.”

Heat, a purely physical phenomenon, is responsible for our tendency to mention it in contexts of anger and arousal, rather than the expressions having a simpler, more direct and effective explanation from genetic, differential survival, sexual selection or libido-suppression perspectives. Studies demonstrate psychological relations between heat and anger (Waggoner 2010, Kiyatkin 2010), heat and sexual arousal (Kiyatkin 2010, Aronov and Fee 2012), and heat and speed (Aronov and Fee 2012). Angry and aroused male mice (Kiyatkin 2010), aroused male zebra finches (Aronov and Fee 2012), and chimpanzees observing aggression between other chimps (Parr and Hopkins 2000) experience brain temperature spikes or increases like those evident in humans from the expressions given above, which may have come about as brain temperature spikes evolved to coincide with excitement in a common ancestor to birds and mammals, and was passed on, in both groups, for a very long time, or because it evolved independently at least twice by coincidence. In any case, physical heat in the brain has corresponded to some extent with simple, consequential types of excitement during the evolutionary history of birds and mammals. Cavanaugh et al. (2015) put the relationships between emotions and temperature, light and heaviness, bright and darkness, expansion and contraction and up and down in terms of perceptual dimensions: “To illustrate, Lakoff and Johnson (1980) have noted a metaphorical relationship between anger and the perceptual dimension of temperature, with anger being characterized as “hot.” Waggoner (2010) found that both children and adults agreed that love, hate and anger were described as “hot,” whereas sorrow, fear and shame were described as “cold.” McMullen and Conway (2002) observed that psychotherapy clients describing depression often used metaphors related to weight (I just feel so heavy), darkness (it’s like a black cloud), constriction (I feel trapped) and verticality (I feel so low). To date, however, research has studied relatively few perceptual dimensions and their linkage with emotions.”

Idiomatic references to fluidity and disorder in language can be understood in the same way as references to hot and cold, as direct consequences of the physical situation in the brain, rather than in terms of a conventional metaphor approach like that taken by Lakoff and Johnson (1980).

Male mouse brains heat up at the sight of a potential female behind a barrier, heat up more when the barrier is removed so they can interact, peak at ejaculation, and then cool down rapidly for a period before mouse interactions resume (Kiyatkin and Mitchum 2003). Brain tissue temperature in all areas was found to increase faster than that of muscle. The authors say their findings suggest brain temperature is “a powerful factor affecting various neural functions and an important part of brain mechanisms underlying motivated behavior” (Kiyatkin and Mitchum 2003).

Anderson (2001) says Shakespeare was probably right when he wrote, in Romeo and Juliet:

I pray thee, good Mercutio, let’s retire:

The day is hot, the Capulets abroad,

And, if we meet, we shall not ’scape a brawl,

For now, these hot days, is the mad blood stirring.

Anderson describes the heat hypothesis of violence, which seems to be correct in that hotter people are more disorderly than colder people: “Aggression—as measured by assault rates, spontaneous riots, spouse batterings, and batters being hit by pitched baseballs—is higher during hotter days, months, seasons, and years.” There are, of course, many variables at play in the world of human angriness, but Anderson, like Shakespeare, is probably right to say that heat is one of them (see Baron and Bell 1976, Gorvett 2020).

Shakespeare normally associates heat with anger, violence, and arousal: “In my youth I never did apply / Hot and rebellious liquors in my blood” from As You Like It, “Now, youthful Troilus, do not these high strains / Of divination in our sister work / Some touches of remorse? or is your blood / So madly hot that no discourse of reason, / Nor fear of bad success in a bad cause,” from Troilus and Cressida, “to the fire-eyed maid of smoky war / All hot and bleeding will we offer them”, from Henry IV, “My mistress made it one upon my cheek: / She is so hot because the meat is cold” from Comedy of Errors and “He eats nothing but doves, love, and that breeds hot blood, and hot blood begets hot thoughts, or hot thoughts beget hot deeds, and hot deeds is love” from Troilus and Cressida.

Heat, fire, power, fluidity, light, color, energy, passion and sex are found together in a single word in ancient Sanskrit according to Carl Jung in Psychology of the Unconscious (2011 edition):

“The idea of the Sanskrit têjas suggests the fundamental significance of the libido for the conception of the world in general. I am indebted to Dr. Abegg, in Zurich, a thorough Sanskrit scholar, for the compilation of the eight meanings of this word.

Têjas signifies:

1. Sharpness, cutting edge. 2. Fire, splendor, light, glow, heat. 3. Healthy appearance, beauty. 4. The fiery and color-producing power of the human organism (thought to be in the bile). 5. Power, energy, vital force. 6. Passionate nature. 7. Mental, also magic, strength; influence, position, dignity. 8. Sperma”

Jung says that we think of sex and heat together unconsciously, along with fire, light and god:

“But now we might venture a conjecture, which is already apparent, and which soon will be proven thoroughly, viz., the following chain of associations: the singer—the singing morning stars—the God of tone—the Creator—the God of Light—(of the sun)—(of the fire)—and of love."

"The links of this chain are proven by the material, with the exception of sun and fire, which I put in parentheses, but which, however, will be proven through what follows in the further course of the analysis. All of these expressions, with one exception, belong to erotic speech. (‘My God, star, light; my sun, fire of love, fiery love,’ etc.)”

The expressions apply as much to angry speech as they do erotic speech, and could be more generally thought of as exciting speech. A brain temperature mechanism probably provides a simpler explanation than libido for the coincident use of similar expressions and qualities to describe violence, sex and god. It also probably explains why Freud and Jung thought of the libido as a fluid:

“The chief source of the history of the analytic conception of libido is Freud's 'Three Contributions to the Sexual Theory.' There the term libido is conceived by him in the original narrow sense of sexual impulse, sexual need. Experience forces us to the assumption of a capacity for displacement of the libido, because functions or localisations of non-sexual force are undoubtedly capable of taking up a certain amount of libidinous sexual impetus, a libidinous afflux. Functions or objects could, therefore, obtain sexual value, which under normal circumstances really have nothing to do with sexuality. From this fact results the Freudian comparison of the libido with a stream, which is divisible, which can be dammed up, which overflows into branches, and so on” (Jung et al. 2011).

Interestingly, Jung (2011) also suggests a kind of alternation between outward and inward flow about the workings of libido and the opposing objects of its frustration:

“Just as the normal libido is comparable to a steady stream which pours its waters broadly into the world of reality, so the resistance, dynamically considered, is comparable, not so much to a rock rearing up in the river bed which is flooded over or surrounded by the stream, as to a backward flow towards the source. A part of the soul desires the outer object; another part, however, harks back to the subjective world, where the airy and fragile palaces of phantasy beckon.”

Fluidity and solidness

Works cited

Anderson, Craig A. “Heat and Violence.” Current Directions in Psychological Science, vol. 10, no. 1, 2001, pp. 33–38., doi:10.1111/1467-8721.00109. Link to article.

Aronov, Dmitriy, and Michale S. Fee.Natural Changes in Brain Temperature Underlie Variations in Song Tempo during a Mating Behavior.” PLoS ONE, vol. 7, no. 10, 2012, doi:10.1371/journal.pone.0047856.

Baron, Robert A., and Paul A. Bell. "Aggression and heat: The influence of ambient temperature, negative affect, and a cooling drink on physical aggression." Journal of personality and social psychology 33.3 (1976): 245.

Brettler, Marc Zvi, et al. The New Oxford Annotated Bible with the Apocryphal/Deuterocanonical Books: New Revised Standard Version. United Kingdom, Oxford University Press, 2007.

Cavanaugh, Lisa A., et al. “Perceptual Dimensions Differentiate Emotions.” Cognition and Emotion, vol. 30, no. 8, 2015, pp. 1430–1445., doi:10.1080/02699931.2015.1070119.

Jung, C. G., and Beatrice M. Hinkle. Psychology of the Unconscious. Barnes & Noble, Inc, 2011. Apple Books.

Gorvett, Zaria. “The Troubling Ways a Heatwave Can Warp Your Mind.” BBC Future, BBC, 17th August 2020.

Kiyatkin, Eugene A. “Brain Temperature Homeostasis: Physiological Fluctuations and Pathological Shifts.” Frontiers in Bioscience (Landmark Edition), U.S. National Library of Medicine, 1 Jan. 2010,

Kiyatkin, E. A., and R. D. Mitchum Jr. "Fluctuations in brain temperature during sexual interaction in male rats: an approach for evaluating neural activity underlying motivated behavior." Neuroscience 119.4 (2003): 1169-1183.

Lakoff, George, and Mark Johnson. Metaphors We Live By. University of Chicago Press, 1980.

McMullen, Linda M., and John B. Conway. "Conventional metaphors for depression." The verbal communication of emotions: Interdisciplinary perspectives (2002): 167-181.

Parr, L.A, and W.D. Hopkins. “Brain Temperature Asymmetries and Emotional Perception in Chimpanzees, Pan Troglodytes.” Physiology & Behavior, vol. 71, no. 3-4, 2000, pp. 363–371., doi:10.1016/s0031-9384(00)00349-8.

Waggoner, John E. “Temperature-Based Metonymies for Emotions in Children and Adults.” Psychological Reports, vol. 106, no. 1, 2010, pp. 233–245., doi:10.2466/pr0.106.1.233-245.

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