Human palm-up and palm-down hand gestures communicate about what Bateson has termed the “contingencies of social relationship” (1987, p. 372). Respectively, the gestures communicate about deference (as in a submissive social posture) and assertiveness (a dominant social pose). Palm-up-and-down cues have neural roots in an ancient, shared caudal-hindbrain, rh8-upper-spinal-cord compartment that links laryngeal communication and vocalization to pectoral communication and gesture (Bass and Chagnaud 2013). The present paper provides observational data from three spoken conversations to explore the generally contrastive meanings of palm-up and palm-down cues in face-to-face interaction. It goes on to explore the gestures’ neural circuitry, in the human nervous system, and traces the likely evolution of these human circuits to those of precursor vertebrates. The paper concludes with a “superimposition theory” to help explain the origin of human language. It is hypothesized that the older system of social communication--exemplified in today’s palm-up-and-down gestures--is a likely forerunner of the newer communication system evident in speech.
Bioneurology; Gesture; Language origins; Nonverbal communication
* Palm-up-and-down gestures are rooted in caudal hindbrain and upper spinal cord.
* Observations show palm-up signs to be essentially deferential in meaning.
* Palm-down signs are more assertive in tone.
* As social signals, palm-up-and-down cues predate vocal and gestural language.
* They suggest an earlier sign system upon which language was superimposed.
PALM-UP AND PALM-DOWN GESTURES: PRECURSORS TO THE ORIGIN OF LANGUAGE
1. OVERVIEW OF PALM-UP-AND-DOWN
Palm-up and palm-down hand gestures often accompany words spoken in face-to-face conversations, and are used widely throughout the world (Morris 1994, Kendon 2004). From observations of usage in videos of three face-to-face conversations, the former (supinated) cues are glossed as deferential, in Goffman’s (1956) sense of the term, while the latter (pronated) cues are more assertive and dominant in tone (see below: 2. THE MEANING OF PALM-UP VS. PALM-DOWN). Analysis of socio-emotional and semantic dimensions of palm-up-and-down gestures also reveals bipolar contrast. Palm-up associates well with emotional uncertainty and semantic indefiniteness--while palm-down associates with feelings of certainty and semantic definiteness (see below: 3. ANALYTIC DIMENSIONS FOR PALM-UP-AND-DOWN CUES).
Neurologically, both hand gestures are pectoral-area bodily signs that link to laryngeal vocalization through an ancient chordate, upper-spinal-cord and caudal-hindbrain compartment (Bass and Chagnaud 2013). Controlled by cord circuits for tactile-withdrawal, palm-up cues are fundamentally submissive-like and deferential. Mediated by basal-ganglia brain circuits, palm-down cues, by contrast, are more dominant-like and assertive (see below: 4. BIONEUROLOGY).
In the palm-up speaking gesture, a hand or both hands rotate to an upward, or supinated, position with the fingers partially or fully extended. The arm may be held straight or flexed at the elbow; the wrist may be flexed or extended. Palm-up most often associates with speaking, but also may be used while listening.
Palm-up cues have diverse linguistic labels, including “raised open hands” (Darwin 1872); “cupped” and “extended hands” (Birdwhistell 1952, 1970); “hand shrugs” (Ekman and Friesen 1968); “baring the palms” (Hass 1970); “bowl-like gestures,” “palms oriented upward” (Scheflen 1972); “palm-rotations,” “palm-shows,” and “palm-up” cues (Givens 1982, 2005); “hands up” gestures (Engel 1978); “holding out a hand” (Waal 1982); “hand cradle,” “hands shrug,” and “palms up” cues (Morris1994); “palm-addressed” cues and “palm presentations” (Kendon 2004); “palm up open hand” (“PUOH”) cues (Muller 2004); “cup,” “lid,” and “tray” cues, and “flat open hand with palm turned upwards” (Mittelberg 2008); “open-handed supine” gestures (Streeck 2009); “holding” cues and “palm-up cyclic” gestures (Ladewig 2011); “hand flips,” “open-palm” gestures (Ferre 2012); and “conduit” gestures (McNeill 2012).
Palm-up cues have diverse interpretations as well. Darwin (1872) interpreted them as expressions of apology and helplessness. Birdwhistell (1970) characterized palm-up linguistically, as having the grammatical structure of speech. Ekman and Friesen (1968) viewed hand-shrugs as signs of helpless uncertainty and confusion. Ferre (2012) pictured palm-up as a marker of speaker prosody and intonation. Mittelberg (2008) viewed cupped hands as vessels to carry ideas. Muller (2004) saw palm-up as a means by which speakers “hold” and present ideas to listeners. Streeck (2009) viewed palm-up as a device to coordinate speaking turns.
In a previous publication (Givens 2015), I reported that by themselves or in combination with other hand movements--such as reaching, showing, and pointing--palm-up cues are used to begin speaking turns, ask questions, request favors, and share personal opinions, feelings, and moods. The palm-up hand movement is a possibly universal signal of deference, in Goffman’s (1956) sense of the term, not unlike other deferential body-motion cues such as the anjai mudra, bow, curtsy, genuflection, kowtow, namaste, poussi-poussi, pranama, sampeah, and wai.
In the palm-down gesture, a hand or both hands rotate to a downward, or pronated, position with the fingers partially or fully extended. The arm may be held straight or flexed at the elbow; the wrist may be flexed or extended. Palm-down cues may or may not be reached out to listeners. In spoken conversations, palm-down gestures are most frequently used by speakers, yet at times by listeners as well.
Palm-down is an insistent gesture in which the hands and forearms assume the prone position used in a floor pushup. Palm-down cues have diverse linguistic labels, including "push away" (Darwin 1872); “flat” gesture (Grant 1969); “push” gesture (Brannigan and Humphries 1972); “batons” (Efron 1972; Ekman and Friesen 1969); “palm-down cues” (Givens 1982, 2015); “palm-down signs” (Norton 1983; diagnostic of a dramatic or dominant nonverbal style); “palms down” (Morris 1994; a worldwide speaking gesture used to "hold down" an idea or "calm down" the mood of an audience (pp. 194-95); “open hand prone gestures” (Kendon 2004; ". . . all share the semantic theme of stopping or interrupting. . ." [p. 248]); and "beat gestures" (Ferre 2012).
Like palm-up, palm-down cues have diverse interpretations. Darwin (1872) interpreted them as gestures of disgust, annoyance, and self protection (defensiveness, to "guard oneself against" attack [p. 256]). Ekman and Friesen (1969) saw them as gestures used to emphasize speech. Blum (1988) analyzed “palms turned toward the floor” as dominance signals. Morris (1994, p. 195) glossed palms front (made with hyperextended wrists and pronated palms) as showing "I disagree." Kendon (2004, p. 248) saw open hand prone gestures as expressive of stopping, interrupting, and denial. Givens (1982) analyzed palm-down as an assertive speaking gesture used in arguments.
By themselves or in combination with other hand movements--again, such as reaching, showing, and pointing--palm-down cues are used to emphasize speaking points, give directions, express disagreement, and dictate commands. The palm-down hand is a possibly universal gesture of assertion, not unlike other commanding body-motion cues such as the raised fist, triumph display, forefinger point, ground-slap, hands scissor, overhand beat, chest beat, palm thrust, military goose-step, and sumo wrestler’s stomp in the ring. All are pronated limb positions used to show assertiveness, dominance, and strength. As will be shown, in form, function, and significance, palm-down assertion cues precisely complement palm-up cues of politeness, deference, and tact.
1.3 Gestural Fossils
Palm-up-and-down hand cues are social gestures. They convey little other than social information, most notably about interpersonal deference and self-assertion. Unlike pointing (deictic) or mime (pantomime-like) cues, which refer to objects and actions outside in the extra-personal environment, palm-up-and-down cues express information about the contingencies of social relationships.
Following Bateson (1987), I propose that the meanings of palm-up-and-down gestures are less about the semantic content of specific accompanying words than about what Bateson has called the “contingencies of relationship” between speaker and listener (p. 372). From feline communication (of Felis catus), he introduced the notion of “μ-function” (after the Greek letter mu; a play on the English word mew, for the crying sound of a cat).
“When your cat is trying to tell you to give her food,” Bateson writes, “how does she do it? She has no word for food or for milk” (1987, p. 372). Instead of speaking, a cat communicates through characteristic nonverbal signs (e.g., mewing, nuzzling, and tail-up posturing) of a dependent kitten. Instead of “Milk!” the cat essentially says “Mama!” The latter message, Bateson maintains, is a nonverbal statement of dependency. Instead of using words the cat “talks in terms of patterns and contingencies of relationship” (Bateson 1987, p. 372).
The μ-function of a palm-up hand is essentially a relationship message of deference (a socially compliant position) while the μ-function of a palm-down hand is about assertion (a more dominant social stance). Both are “gestural fossils,” and are far older than other expressive hand movements, postures, and signals. With roots in the tactile-withdrawal reflex (spinal), palm-up is older than palm-down, which itself has roots in the brain’s basal ganglia (see below: 4. BIONEUROLOGY). That our closest primate relatives, the chimpanzees (both Pan troglodytes and paniscus), appease with palm-up gestures (e.g., Waal 1982) and assert with palm-down (using pronated “slap-ground” gestures) (e.g., Berdicio and Nash 1981, Goodall 1990) attests to the phylogenetic antiquity of palm-up-and-down cues as social signs. As will be suggested, these ancient hand gestures provide a window through which to glimpse the older communication system upon which human language may rest.
2. THE MEANING OF PALM-UP VS. PALM-DOWN
Palm-up-and-down gestures are often used in face-to-face, conversational settings. Four decades ago Goffman (1967) delineated the subject matter of face-to-face interaction: "It is that class of events which occurs during co-presence and by virtue of co-presence. The ultimate behavioral materials are the glances, gestures, positionings, and verbal statements that people continuously feed into the situation, whether intended or not" (p. 1). The present report focuses on the meaning of palm-up-and-down gestures exchanged by college-student volunteers, co-presently engaged with one another in face-to-face interaction.
Data were collected from three, eight-minute videos of dyadic conversations between subjects “Gail,” “George,” and “Kris.” The student volunteers--Gail (age 24), George (22), and Kris (20)--are native-born, English-speaking Americans of European descent, who were unacquainted with each other or with the researcher.
Subjects were told they were to be participants in a linguistic study of conversation (the nonverbal focus was undisclosed). Instructions were given to get to know the partner by "talking about school activities, hobbies, travel, movies, or whatever interests you." For each conversation the researcher turned on the video camera and left the room.
Videos were then reviewed, and both the linguistic and nonlinguistic behaviors were recorded on data sheets (Givens 1982, Table II; numbers in brackets, e.g., , indicate line(s) in the data sheet where behaviors occurred). All nonverbal signs were synchronized to the speaking activity, recorded in standard English orthography (linguistic primary stress is indicated by capitalization, e.g., “PRImary”). In temporal terms, the gesture measurements are relative rather than absolute, as each body movement was observed to come before, during, or after another body-motion unit or speech event, including words, voice quality, vocal register, intonation, and clause-terminal pitch.
2.3 Conversational Palm-up-and-down
In her conversations Gail--a self-defined political activist--was the most assertive of the three students. Her palm-up cues were often directed (reached) toward partners with an aggressively extended index finger (for analysis of the pointing gesture, see Givens 2015). Many of her palm-up gestures graded into the more adamant and assertive palm-down cue. In her conversations, Kris, who reported enjoying sports and Hawaiian vacations, frequently smiled, was apolitical, and avoided verbal disagreement with partners.
George’s conversation with Gail was argumentative. As he hemmed (hesitated while speaking), hawed (fumbled for words), and haltingly repeated himself in a dispute over women’s roles in the workplace, palm-up gestures were accompanied by shoulder-shrugs. He shrugged, for instance, when saying, “And it’s, it’s, you [shoulder-shrug] know, you know, about the only thing you can DO is CURSE it [since, he might have added, you can’t actually do anything about women’s unequal pay]” [140-41].
In contrast, George’s conversation with Kris was friendly, cordial, and flirtatious. For both participants, episodes of smiling, laughing, sideward head-tilting, hair-preening, and additional “courtship-readiness” signs (Givens 2005) were commonplace. Indecisive, palm-up gestures were given when George said, “I’m just kind of, well, I [palm-up] don’t know just what exACTly I WANT to get into, you know, as far as, um, you know, things go. . .” [68-70].
2.4 Summary Results: Palm-down
George used 16 palm-down gestures, exclusively with Gail. His palm-down movements accompanied ostensibly firm, decided statements in argumentative contexts. There was no apparent doubt, but rather an assertive expression of conviction and certainty embodied in George’s pronated-palms.
Gail used palm-down hand movements seven times with George and 13 times with Kris. The pronated movements expressed emphasis as they accompanied primary vocal stress and an overloud voice. Her palm-down movements were interpreted as assertions of confidence and emotional certainty. They contrasted with palm-up movements given as she shrugged her shoulders and expressed uncertainty (see below: 4.2 Palm-up Deference).
Kris used downward, pronated-hand movements seven times with Gail and four times with George. Her palm-down was used twice in argumentative verbal contexts to emphasize speaking points. It occurred twice near the end of her conversation with Gail, with non-argumentative statements accompanied by an overloud voice. Her palm-down movements were ostensibly assertive and added a sense of conviction and confidence to Kris’s words.
2.5 Summary Results: Palm-up
A major meaning category for palm-up cues in the videos is uncertainty. As she spoke to George, Gail's palm-up gestures co-occurred with vocally expressed uncertainty (e.g., "I forget," "I guess," and "well . . ."). George used palm-up cues in contexts of uncertainty with Gail, as he said "maybe” (“an uncertain reply” [Soukhanov 1992, p. 1113]), and with Kris when he said, “Well, I haven’t really, haven’t really [touch-nose] deCIded yet. I think pro’lly [probably: “Likely but uncertain” (Soukhanov 1992, p. 1443)], I’ll pro’lly, I’ll pro’lly go, you [palm-up] know, past four years” [66-7].
3. ANALYTIC DIMENSIONS FOR PALM-UP-AND-DOWN CUES
Data analysis led to three heuristic conceptual dimensions for palm-up and palm-down gestures in the videos: (1) Social, (2) Emotional, and (3) Semantic. The values and variables of each dimension are outlined below:
(1) Social: Defer vs. Assert
Analysis of the conversations suggested that social deference and assertiveness are core meanings, respectively, for palm-up and palm-down cues. To defer is to “submit to the opinion, wishes, or decision of another” (Soukhanov 1992, p. 489). To assert is to “put (oneself) forward boldly or forcefully in an effort to make an opinion known” (Soukhanov 1992, p. 111).
Deferential words and phrases include (1) “all I’m saying,” (2) “go ahead” (you may continue), (3) “just” (merely), (4) "kind of" (verbal hedge, linguistic “de-precision” device), and (5) “sort of” (verbal hedge, de-precision). Each of these linguistic constructions was accompanied by palm-up gestures.
Assertive words and phrases include (1) “can’t,” (2) “don’t,” (3) “no,” (4) “not,” and (5) “unfair.” (Assertive constructions often involve negation, as negation categorically rules out and nullifies.) Each of these linguistic constructions was accompanied by palm-down gestures.
(2) Emotional: Uncertainty vs. Certainty
Analysis found values of uncertainty and certainty, respectively, to be characteristic of palm-up and palm-down cues. To be uncertain is “Not having sure knowledge . . .” (Soukhanov 1992, p. 1942). A key English synonym is “doubt.” To be certain, on the other hand, means “Established beyond doubt or question . . .” (Soukhanov 1992, p. 313). Feelings of certainty or uncertainty have been characterized as human emotions (MacLean 1990, Damasio 1994, Kagan 2007).
Uncertain words and phrases in the videos, accompanied by palm-up gestures, include the following: (1) “anyway” (as in “in any manner whatever”), (2) “I don’t know,” (3) “I forget,” (4) “maybe” (as in “possibly”), (5) “probably” (as in “presumably”), (6) “what,” and (7) “whatever.” Each of these linguistic constructions was accompanied by palm-up hand gestures.
Certainty-connoting words and phrases in the videos include the following: (1) “but” (as in “on the contrary”), (2) “gone” (as in “past”), (3) “off” (as in “so as to be completely removed, finished, or eliminated”), and (4) “there’s a difference” (as in “the quality of being unlike”). Each of these linguistic constructions was accompanied by palm-down gestures.
(3) Semantic: Indefinite vs. Definite
Not unlike an English indefinite pronoun such as “any” or “some” (which does not specify the identity of its object), indefinite semantic constructions are unspecific and do not identify their relational, material, or spatial referents. In the videos, they include (1) “and so forth” (unspecified items in a series), (2) “if” (as in if something unspecified should happen), (3) “something” (as in an unspecified or indefinite thing), (4) “sometimes” (as in an unspecified time), and (5) “somewhere” (as in an unspecified or unknown place). Each of these linguistic constructions was accompanied by palm-up hand gestures.
Definite semantic constructions are basically declarative sentences used to assert that a statement is specific, clearly defined, and factual. In the videos, they include (1) “I consider myself a socialist,” (2) “air travel gets more common and cheaper,” (3) “it turned a lot of people off,” (4) “I’m not interested in chemistry,” and (5) “I had a really bad teacher.” Each of these more definite linguistic constructions was accompanied by palm-down hand gestures.
3.1 Gesture Cube
Conceptual dimensions for palm-up-and-down cues may be plotted on a 3-dimensional cube graph, in which the X-axis is social, the Y-axis emotional, and the Z-axis semantic.
In this graphic space, palm-up hand cues--which tend to be deferential, uncertain, and indefinite--cluster in the cube’s left-bottom-front corner. Palm-down cues--which have qualities of assertiveness, certainty, and definiteness--cluster in the right-top-back corner of the cube. Socially, emotionally, and semantically, palm-up and palm-down hand gestures are as far as possible removed and separated from one another at opposite corners of the cube. Indeed, palm-up and palm-down plot as complementary, mirror-polar opposites.
To explain the fundamental contrast between palm-up and palm-down hand gestures in the videos, we turn to bioneurology and recent discoveries in evolutionary neuroscience. Along with other hand gestures, palm-up-and-down cues originated in a common brain area that is hundreds of millions of years older than either sign language or vocal speech (see below: 4.1 Hand Gestures and Speech). Moreover, while palm-up is mediated by older spinal circuits below the brain, the more recent palm-down cue is controlled by newer circuits within the brain itself.
4.1 Hand Gestures and Speech
Beginning circa 500 million years ago in the chordate brain and spinal cord--in a shared caudal-hindbrain, rh8-upper-spinal compartment--circuits for vocal-laryngeal and gestural-pectoral communication provided neural linkage between vibratory-respiratory and forelimb-motion cues (Bass and Chagnaud 2013). That palm-up-and-down hand motions accompany speech is due wholly or in part to these neural fiberlinks between vocalizing via the larynx and gesturing with forelimbs and hands. Muscles that today move the larynx and pectoral-girdle evolved from hypobranchial muscles that originally opened the mouths and gill openings of ancient fishes.
Like all animal signs--from the ”hand waving of lizards, singing of whales or nightingales, cries of migrating geese, squeaking of mice, grunts of baboons“ (Trevarthen et al. 2011, p. 13)--palm-up-and-down gesticulations are adapted primarily for social communication. They differ little in fundamental meaning from the gorilla’s (Gorilla gorilla) chest-beating, the catfish’s (Synodontis schoutedeni) pectoral-fin squeaks, or the humpback whale’s (Megaptera novaeangliae) pectoral flipper-slaps. All are pectoral gestures tendered to announce physical presence. All may be accompanied, variously, by laryngeal signals such as words, vocal roars, drumming sounds (produced by swim bladders), or “singing” (emitted from a whale’s respiratory system).
4.2 Palm-up deference
A major meaning category for palm-up cues is uncertainty (Givens 2014b). Though not often classified as such, uncertainty is an emotion (Kagan 2007), a feeling of indecision, misgiving, or doubt. According to Damasio (1994), an uncertain feeling is a secondary emotion, mediated by the limbic system (via the amygdala and anterior cingulate gyrus), and is linked to cognitive thought processes by circuitry in prefrontal, sensory, and association modules of the cerebral cortex. Like facial muscles that activate expressions of primary emotion--such as happiness, sadness, and anger--the shoulder’s upper trapezius muscle, which activates shrugging and collateral palm-up movements, is linked to limbic-brain modules via special visceral efferent (“emotional”) rather than by somatic (“unemotional”), nerves.
4.2.1 Shoulder shrug
An argument in favor of uncertainty’s emotional status is its involvement in the larger shoulder-shrug display of helpless uncertainty (Givens 1977). The palm-up gesture itself is one of 13 constituents in a larger, shoulder-shrug display of uncertainty (Givens 2014b). The display, which also includes a lateral head-tilt to the right or left side, originates from a protective crouch posture innervated by circuits for flexion withdrawal. The shoulder-shrug display was first identified by Darwin (1872), who noted instances of shrugging as a cue of helplessness in aboriginal Australia and North America, Africa, India, Malaya, and Micronesia.
In the shoulder component of the larger display, upper trapezius (mediated by CN XI, a special visceral nerve) and levator scapulae muscles lift the scapulas. Trapezius (assisted by pectoralis major, p. minor, and serratus anterior) medially rotates (i.e., ventrally flexes) the shoulders, as well. These muscular movements are incredibly ancient. "The trapezius of terrestrial vertebrates,” Cartmill and colleagues write, “seems to be derived from a muscle sheet in fish that runs down from the back of the head to the top of the gill-arch bones. In a fish, this muscle lifts the whole set of gills up dorsally when it contracts" (Cartmill et al. 1987, p. 224).
As a branchiomeric muscle, upper trapezius--like the facial muscles of expression--is emotionally responsive and may contract by other than conscious means. Upper trapezius is innervated by the accessory nerve (cranial XI), a special visceral nerve that also feeds into the larynx; thus, shrugs and softer, higher-pitched (i.e, submissive-like) voice tones may be given in tandem.
Why does a palm supinate when one asks a question? On the efferent (outgoing or production) side, upraised palms are gestural byproducts of an ancestral crouch display, a protective vertebrate posture designed to be defensive rather than offensive. Neural roots of palm-up cues reach back further in time than palms themselves--at least 500 million years--to protective nerve circuits for flexion withdrawal. These circuits reflexively bend the ancestral body wall--and later the neck, arms, and legs--away from danger. In monkeys, Graziano (2010) found that electrical stimulation of the brain’s polysensory area (in the precentral gyrus) elicits defensive shoulder shrugging, a movement that occurs naturally in response “. . . to tactile stimuli on the face and to visual stimuli looming toward the tactile receptive fields” (p. 462).
4.2.2 Neck reflexes
That palms and forearms rotate upward in shrugging is due to actions of primeval neck reflexes originally designed for locomotion (Ghez 1991). Note that palm-up cues tend to be one-handed (unilateral) when stimulated by sideward head turns and tilting the head left or right, but two-handed (bilateral) when the neck bends forward or backward (Ghez 1991). We do not ordinarily make conscious choices about these gestures. Emotions responsible for palm-up movements are located above the spinal cord in defensive areas of the forebrain's limbic system (notably the amygdala), passing through basal ganglia and brain-stem links to the spinal cord below. The emotional brain unthinkingly touches off flexor-withdrawal movements designed to protect from real or imagined harm.
4.2.3 Mirror neurons
On the afferent (incoming or reception) side, mirror neurons provide brain circuitry that enables us--intuitively--to decode and understand the meaning of palm-up cues. When we see a palm-up hand gesture, mirror neurons set up a motor template, a prototype or blueprint in our own brain, that allows us to read the cue. Through links to the limbic system, additional mirror neurons help us decode the gesture’s emotional nuances. “What has emerged from mirror-neuron research is that we are seemingly wired to interpret the nonverbal actions of others as if we ourselves were enacting them” (Givens 2014a, p. 78).
4.2.4 Unified system
According to Xu and colleagues, both gestural-visual and vocal-auditory stimuli “. . . activate a common, left-lateralized network of inferior frontal and posterior temporal regions in which symbolic gestures and spoken words may be mapped onto common, corresponding conceptual representations. We suggest that these anterior and posterior perisylvian areas [Broca’s and Wernicke’s areas, respectively], identified since the mid-19th century as the core of the brain's language system, are not in fact committed to language processing, but may function as a modality-independent semiotic system that plays a broader role in human communication, linking meaning with symbols whether these are words, gestures, images, sounds, or objects” (Xu et al. 2009).
Consistent with Bass and Chagnaud’s (2013) finding that hand gestures and words are neurologically coupled, Guellai and colleagues consider gestural and vocal prosody (or intonation) to be a unified system: “We draw the conclusion that spontaneous gestures and speech form a single communication system where the suprasegmental aspects of spoken language [i.e., prosody] are mapped to the motor-programs responsible for the production of both speech sounds and hand gestures” Guellai et al. (2014).
4.3 Palm-down assertion
Major meaning categories for palm-down gestures include the expression of personal certainty and interpersonal assertion (a dominant-like social stance). Palm-down cues mark emotional feelings of certitude (Givens 2014). Though not often classified as such, certainty is an emotional feeling that something is real, right, and true. Feelings of certainty come not from brain areas that mediate rationality and conscious reflection, but from evolutionary older emotion centers of the limbic brain (MacLean 1990, p. 17). These areas include the cingulate gyrus, amygdala, hippocampus, hypothalamus, ventral tegmentum (pleasure pathway), and supraorbital cortex (Burton 2008, p. 127).
4.3.1 High-stand display
To make a verbal statement emotionally stronger, palms rotate downward as if preparing the body to press-up to an aggressive, gravity-defying high-stand. The amygdala (acting through reptilian areas of basal ganglia [MacLean 1990, Grillner 1996]) mediates palm-down gestures. That we show dominance by pronating, extending, and figuratively stomping with our forelimbs reflects the amygdala's evolutionary kinship with the basal ganglia. While the former directs an emotional stance, the latter governs a physical stance in relation to gravity. Thus, slapping a desktop for emphasis is not unlike a sumo wrestler's ceremonial stomp in the ring. Both are postural displays to demonstrate stability, strength, and standing on the earthly plain.
There are fundamental differences in the evolution of forelimb and hindlimb communication. In the tetrapod transition from water to land, forelimbs functioned as tactile antennae to sense the tangible boundaries between water and land. Thus, from the very beginning pectoral forelimbs played an exploratory role in their direct communication with the tactile properties of terra firma. In this matter pelvic hindlimbs played a secondary role. Moreover, pronated forelimbs enabled early amphibians to crawl forward on land, and to raise the head and pectoral portion of the body above shallow waterlines. Evolution of hindlimbs, meanwhile, was secondary and played a lesser role in communication than in supporting body weight on dry land.
High-stand postures in tetrapods date back perhaps 365 million years to fossils of the oldest known North-American amphibian, Hynerpeton bassetti, that show forelimbs strong enough to do a pushup akin to the socially assertive press-up postures of today's lizards, basilisks, and iguanas. In reptilian neurology, the basal ganglia-ansa lenticularis pathway reverberated links between the amygdala and basal ganglia via the ansa lenticularis and lenticulate fasciculus to the midbrain tegmentum, red nucleus, and reticular system to spinal cord interneurons required for the high-stand display. In human neurology, palm-down gestures derive from postural signs mediated by basal ganglia via the brain stem's reticulospinal tract to motor neurons acting on muscles that control stance in relation to gravity.
4.3.2 Looming larger
The vertebrate visual system is reflexively designed to warn of danger from threateningly large, potentially dangerous looming objects. Doing a pushup to appear “bigger” is part of the evolutionary pattern of employing size as a communicative device to assert oneself and show strength.
Movements and postures of expansion evoke a strong, automatic reaction known as the looming response, seen in birds just three hours after hatching, and in puppies at two weeks of age. At 14 days, human infants will avoid a rapidly dilating shape projected to "loom" on a screen--as if they already knew the danger portended by large objects. A steady increase in the size of a projected shadow also produces avoidance movements in frogs, chicks, and turtles (Russell 1979).
220.127.116.11 Pisces power
Early fishes may have turned the widest parts of their bodies toward rivals, just as modern cichlid, puffer, and cod fish do today (Marshall 1965) to exaggerate physical size and assert social presence visibly through illusions of “bigness.”
18.104.22.168 Chameleon clout
Following pisces, amphibians (e.g., frogs) puff up fraudulently--or deceptively deflate, as the situation warrants--to threaten or yield. Of the toad, Porter writes, "It will inflate its body with air, making itself appear much larger, or it will bow its head forward, thus forming its body into a crouched ball" (1967, p. 40). Chameleons turn a broadside toward enemies to visually "expand" in size, or crouch down to lower their profile and "shrink" (Cloudsley Thompson 1976).
22.214.171.124 Saurian size
Lizards stiffen all four legs in aggressive high-stand displays. Even limbless snakes appear "bigger"--or "smaller"--through illusory size. To threaten, the hognose snake rises vertically, widens its head like a cobra, thrusts its body forward, and makes loud hissing noises. But to surrender, it reverses the display: gasps feebly, rolls over on its back, shudders, and plays dead (Porter 1967).
126.96.36.199 Mammalian mass
Cats, dogs, and other fur-bearing mammals may “enlarge” through piloerection (big hair). Like fish and lizards, cattle turn a broadside when threatened to show their biggest, most fearsome angle. The antelope's dark dorsal line frames its broadside silhouette for illusory size and "nearness."
188.8.131.52 Primate punch
Higher primates show dominance by straightening and holding their arms away from the body, or submission by bending and pulling arms into their sides. Mountain gorillas beat broadened chests as body hair erects and the larynx roars.
In summary, from the standpoint of bioneurology, palm-up-and-down gestures have deep evolutionary roots in the vertebrate nervous-system for social communication. Palm-up and palm-down gestures are well adapted for expressing, respectively, key contrasts in deference and assertion.
5. IMPLICATIONS: ORIGIN OF LANGUAGE
From social messages encoded in hand gestures and laryngeal vocalization, we hypothesize a gradual extension of the role of pectoral-laryngeal communication from calling attention to one’s own physical presence to calling attention to--and naming--objects in, and features of, the environment.
As social gestures, palm-up-and-down hand signals call attention to a sender’s physical presence. Like chest beating, ground slaps, and pectoral-fin slapping, they are cues to announce presence: “I am here.” Nonverbally, the most basic meaning of any hand gesture is, “I am physically present.” As the poet Paul Celan wrote about handshaking, “The handshake is our decided ritual of both asserting I am here and handing over (here) a self to another” (Rankine 2004, p. 120; parentheses in original quote removed). Celan’s poetic rendition of the handshake would also hold for palm-up-and-down gestures.
To reiterate, language is likely an extension of calling attention to oneself to calling attention to external actions and objects. Indeed, for Homo, object-naming has a special relationship with the fabrication of tools. Neuroscientists have established that flaking a stone tool and uttering a related word or phrase about the act of flaking make use of closely connected brain areas. So nearly alike, in fact, are neural pathways for manual dexterity and speech that the fabricated artifact itself may be deciphered as a paleolithic “word” or petrified phrase.
Language is considered to be between 200-thousand (Lieberman 1991) and two-million (Gibson 1993) years old. It is likely that the ability to communicate with spoken and manual signs--and the ability to manufacture artifacts such as stone tools--evolved in tandem. Some form of communication--showing, miming, and/or speaking--was required to pass the knowledge of tool design from one generation to the next.
Handling, seeing, making, and carrying stone implements likely stimulated conceptual categories for gestures and word labels which aided in teaching the young. Through their relationship with tools and artifacts, it appears that human beings became information-sharing primates of the highest order.
Preadaptations for vocal speech involved the human tongue and larynx. Before saying a word, the tongue had been a humble manager of "food tossing." Through its acrobatic maneuvers, chewed morsels were distributed to premolars and molars for finer grinding and pulping. (The trick was not getting bitten in the process.) As upright posture evolved, the throat grew in length, and the vocal larynx was retrofit lower into the neck. As a result the larynx, originally a mammalian organ for calling and announcing presence, increased its range as the dexterous tongue waited to speak.
5.1.2 Associative learning
Speech involves the ability to pair stored mental concepts with incoming data from the senses. Pavlov observed laboratory dogs as they paired the sound of human footsteps (incoming auditory) with memories of meat (stored mental concepts). Not only did the meat itself cause Pavlov's dogs to salivate, but the mental concept of meat--memories of mealtimes past--was recalled by the sound of human feet. Pairing one sensation with memories of another, known as sensitization or associative learning, is an ancient ability shared by Homo and simpler animals, including sea slugs.
5.1.3 Objects and Artifacts
In human evolution, tool-use likely increased concept formation. MRI studies suggest that children who make early, skilled use of the digits of the right hand (in playing the guitar, e.g.) develop larger areas in the left sensory cortex devoted to fingering (Wan 2010). Thus, Pleistocene youngsters precociously introduced to tool-making may have developed enhanced neural circuitry for the task. While the circuitry itself was not passed on, there was a likely genetic transmission of the neuroplasticity enabling new circuits to adapt. Presumably, those with greater neuroplasticity were better able to make and use artifacts and tools.
An artifact is a material object deliberately fabricated by humankind. Like gestures, artifacts have a great deal to express or "say." The simplest message transmitted by any artifact is, "Something manmade is here" (Givens 1982, p. 172). "Manmade" (i.e., intelligently made by humans) is evident in the deliberately patterned shape, the grammatical syntax (the structured arrangement of parts), and the negative entropy encoded in artifacts as material signs, signals, and cues.
The English word artifact comes from Latin arte ("by skill") and factum ("made"; via the Indo-European root dhe-, "to set," "to put"; skill "by hand" is implied). The earliest known artifacts are stone tools. "At dozens of archaeological sites in Africa, razor-sharp stone flakes and round hammer-stones mark the handiwork of anonymous craftspeople who forged tools as early as 2.6 million years ago" (Gibbons 1997, p. 32). As Hauser (2000, p. 22) has noted, "When we create an artifact such as a tool, we leave a physical trace of our thoughts."
5.1.4 Artifacts and Speech
Anthropologists have long suspected a link between human artifacts and language. Holloway commented on the likely connection in 1969:
"With all due respect to my esteemed colleague [Iain Davidson], our disagreement doesn't really rest so much on whether or not I see a Broca's area on [fossil cranium] 1470, whichever Homo it turns out to be. . . . Our disagreement really stems from whether or not the manufacture of stone tools gives us any insights to previous cognitive behavioral patterns, and as I wrote back in 1969, 'Culture: A Human Domain,' in CA [Current Anthropology], I think there are more similarities than not between language behavior and stone tool making, and I haven't retreated from this position, because I haven't seen effective rebuttal, just denial" (Holloway 1996).
As Gibson (1993) noted, “Object-manipulation skills, social behavior, and language mature in a synchronous and mutually facilitatory fashion” (p. 123). In Tools, Language and Cognition in Human Evolution, Gibson and Ingold (1993) devoted an entire book of readings to the topic, largely confirming that tool making was an important ingredient in the evolution of language.
Recently neuroscientists have identified specific brain modules implicated in the tool-use-language nexus. Consider as an example Iriki’s (2012) abstract for the 2012 conference on "Mirror Neurons: New Frontiers 20 Years After Their Discovery": "The brain mechanisms that subserve tool use may bridge the gap between gesture and language--the site of such integration seems to be the parietal and extending opercular cortices."
It was established early on--after the advent of olfactory communication, certainly, but millions of years before facial expressions, eye contact, or words (both spoken and signed)--that the main articulators for vertebrate social communication would be pectoral (forelimb movements) and laryngeal (respiratory vibration). The information conveyed by these ancestral articulators was fundamentally about physical presence: “I am here,” and the message was delivered deferentially (in a submissive-like manner) or as an assertion of superiority (in more dominant tones).
Palm-up-and-down gestures have stimulated research interest at least since Darwin’s characterization of them in The Expression of the Emotions in Man and Animals (1872). While researchers today agree that palm supination and pronation movements are valid as gestural entities, there is less agreement about their meaning.
From observations recounted in the present study, palm-up-and-down gestures may be construed as cues primarily used to convey information about social relationship. In face-to-face interaction, palm-up is generally deferential while palm-down is more assertive in meaning.
Palm-up-and-down hand gestures have ancient roots and are linked to laryngeal vocalization in a shared hindbrain, upper-spinal-cord region of the vertebrate nervous system. Unlike mime cues--which are hand gestures used to depict physical, spatial, and temporal relationships among objects, activities, and events (Givens 2015)--palm-up-and-down signs do not ordinarily make reference to extra-personal or environmental features of the outside world. In this regard they differ, as well, from deictic cues, in which an extended index finger (most often the index, due to an extra forearm muscle, extensor indicis, which enhances neural control of the muscular ability to point) to indicate the presence or location of environmental objects and their features.
Palm-up-and-down signals thus differ markedly from hand signals used to direct attention to objects apart from the self or apart from one’s immediate interlocutor. The latter hand signals are of more recent origin, coming at a time when human communication expanded from purely social messages to messages about the external world of objects (e.g., animals, plants, artifacts, and so on). As such, the former, older hand signals--which are still in use today--may indeed be regarded as gestural fossils left over from the original vertebrate system of communication about matters of social relationship. Palm gestures are remnants of the ancestral articulators and may be used to reflect back on the social messages our forebears exchanged before the advent of languages and words.
Stimulated by humankind’s seeming fascination with tangible objects that can be held in the hand, and by the fabrication of material artifacts and stone tools, ancestors of Homo sapiens gradually extended the use of pectoral-related body movements and laryngeal vocalizations for social communication to communication about objects and their features, and to the interrelationships of these in space-time. The ancient bodily articulators for linguistic communication were likely there from the very beginning.
To conclude, this paper suggests a theoretical plausibility: human gestural and spoken language was superimposed upon an earlier prelinguistic system of vertebrate social communication to which--by their current widespread usage in face-to-face conversations--palm-up-and-down gestures strongly allude.
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