News on FOXP2

There are some interesting posts on new work done on FOXP2. The human version of the gene, which is implicated in vocal coordination and language in some way among a lot of other functions, was inserted into mice who also possess a version of foxp2 that influences, among other things, erly ultrasonic vocalizations. The brain led to changes in neural organization but otherwise bodily development was normal. One implication of this is that the changes in the human version of FOXP2 probably affect neural development, which is quite an ecxiting find.

There are posts on the paper by Enard et al. over at:

Anthropology.net

Gene Expression

The Loom

Update:

Ed Yong of Not Exactly Rocket Science also has a nice post up on the topic

Six Candidates for What Makes Human Cognition Uniquely Human

One of the key candidates for what makes human cognition unique is of course language and symbolic thought. We are “the articulate Mammal” (Aitchison 1998) and an “animal symbolicum” (Cassirer 2006: 31). And if one defining feature truly fits our nature, it is that we are the “symbolic species” (Deacon 1998). But as evolutionary anthropologists Michael Tomasello and his colleagues argue, “saying that only humans have language is like saying that only humans build skyscrapers, when the fact is that only humans (among primates) build freestanding shelters at all” (Tomasello et al. 2005: 690).

Language and Social Cognition

According to them and many other researchers, language and symbolic behaviour, although they certainly are crucial features of human cognition, are derived from human beings’ unique capacities in the social domain. As Willard van Orman Quine pointed out, language is essential a “social art” (Quine 1960: ix). Specifically, it builds on the foundations of infants’ capacities for joint attention, intention-reading, and cultural learning (Tomasello 2003: 58). Linguistic communication, in this view, is essentially a form of joint action rooted in common ground between speaker and hearer (Clark 1996: 3 & 12), in which they make “mutually manifest” relevant changes in their cognitive environment (Sperber & Wilson 1995). This is the precondition for the establishment and (co-)construction of symbolic spaces of meaning and shared perspectives (Graumann 2002, Verhagen 2007: 53f.). These abilities, then, had to evolve prior to language, however great language’s effect on cognition may be in general (Carruthers 2002), and if we look for the origins and defining features of human uniqueness we should probably look in the social domain first.

Corroborating evidence for this view comes from comparisons of brain size among primates. Firstly, there are significant positive correlations between group size and primate neocortex size (Dunbar & Shultz 2007). Secondly, there is also a positive correlation between technological innovation and tool use – which are both facilitated by social learning – on the one hand and brain size on the other (Reader and Laland 2002). Our brain, it seems, is essential a “social brain” that evolved to cope with the affordances of a primate social world that frequently got more complex (Dunbar & Shultz 2007, Lewin 2005: 220f.). Thus, “although innovation, tool use, and technological invention may have played a crucial role in the evolution of ape and human brains, these skills were probably built upon mental computations that had their origins and foundations in social interactions” (Cheney & Seyfarth 2007: 283).

Language, Mental Representations, and Symbolic Thought

But this of course does not mean that we expect all other unique aspects of human cognition to be derivative of social cognition. The development of higher social cognition only presented the enabling context and cognitive starting point for other human mental capacities to evolve. To pick up the example again, language, for instance, does not only have an interactive function but also a symbolic one. It creates ‘symbolic assemblies’ that function as form-meaning pairings (Evans & Green 2006: 6f.). But the ability to acquire arbitrary symbolic units itself does not appear to be uniquely human, as it has been demonstrated in great apes, parrots, dolphins and dogs (see Tomasello 2008: 254ff.). But there are two essential differences between the symbolic abilities of humans and other animals: First, even with lexigram- or sign language-trained apes there appears to be nothing that even comes close to the production and joint engagement skills possessed by human children (production) or even pre-verbal infants (joint engagement) (Tomasello 2008: 109ff.).

Secondly, human symbols and concepts function as ‘decoupled representations’ which are not directly bound to a reaction pattern as in most other animal species, including symbol-trained animals, and enable significant “response breadth” and planning (Sterelny 2003: 29f.). In addition, symbolic thought and linguistic usage does not only rely on the comprehension and production of arbitrary signs, but essentially depends on our capacity for abstract, relational, analogical, higher-order, hierarchical and role-governed compositional thought. (Deacon 1998, Jackendoff 2007, Penn et al. 2008).

We now have two tentative candidates for what makes us special:

(1) The capacity to develop a shared point of view or “we-perspective” (Tuomela 2007: 46f.) and jointly engage in and attend to shared goals, plans and intentions in a cooperative collaborative activity within a joint attentional frame and a shared frame of reference (Tomasello et al. 2005).

(2) A conceptual system that is able to reinterpret and re-describe sensory as well as cognitive data and store them in an abstract, decoupled format that can be used for symbolic, relational and analogical reasoning (Penn et al. 2008).

We can now imagine a step in evolution where these two capacities were further integrated, yielding the analogical realization that others are “like me” (the capacity developed to

(3) actively attribute mental states to others in the same sense as one experience mental events and states oneself, that is to, have a “theory of mind” (Premack & Woodruff 1978).

Further, an integration of these capacities, and continuing collaborations and mutual engagements in social and other activities, would lead to the emergence of

(4) shared, intersubjectively overlapping frames of references or coordinate systems into which abstract and non-abstract conceptual representations could be integrated and imported in a systematic fashion, and within which shared percepts and concepts could be blended, unified, and related to each other in a role-governed fashion. (Bühler 1934, Fauconnier & Turner 2002).

In short, the first species in the hominin line who developed this capacity would not only have shared a perceptual world with his or her conspecifics, but they would inhabit a shared mental world. In this collective “we-perspective” and shared frame of reference mediated by joint engagement, they would then be able to create a shared “symbolic niche” in which meaningful cultural practices and shared symbolic constructs, such as institutions, could be co-created and which would ‘come alive’ and have actual real-world significance (Harder fc, Tuomela 2007). By jointly attending to and attaching meaning to cultural artefacts and practices homo gave them intersubjective value and reality and created ‘institutional realities’ (Searle 1995, Moll & Tomasello 2007). It is probable that from the dawn of human culture cognition accelerated in a spiralling and cumulative cognition-culture feedback loop

Additionally, when we are able to project ourselves and others into the same frame of reference, and can also project more abstract symbolic units into this coordinate system, it follows that along and co-evolving with these other changes a capacity

(5) for projecting ourselves and others backwards or forwards into past and future situations is probable to have evolved, that is, a capacity for mental time travel, including the ability to retrieve and re-live episodic memories of past autobiographical events (Tulving 2005) as well as prospective foresight enabling the planning of future actions and events (Suddendorf & Corballis 2007).

Finally, these changes were certainly accompanied co-evolutionary by a means of externalising shared proto-concepts and communicatively coordinating cooperative activities in a flexible manner via the vocal and gestural level. (Hurford 2007, Tomasello 2008). At some time, concepts became public, that is “they became the sorts of things that lots of people can, and do, share” (Fodor 1998: 28).

It is conceivable that “building upon pre-existing representational schemes in animals” (Hurford 2007: 140), and a general perceptual and cognitive machinery that scaffolded them (Jackendoff 2007: 388), ever increasing linguistic abilities and concepts evolved step by step. They probably did evolve from the proto-concepts we can see in the higher mammals of today into the pre-linguistic concepts that are argued to exist in some of the other great apes (especially those individuals who are enculturated and symbol-trained) and then into some form of proto-language (Bickerton 2009). At some time, this proto-language with already quite sophisticated conceptual representations then evolved into the fully human language we know today.

In summary, a truly human language faculty evolved, which is

(6) a collection of unique mental structures – phonology (externalisation) and syntax (merging constituents (A + B = [AB] and creating blended new ‘mental building blocks’ which can be merged with other constituents recursively [AB] + C = [ABC]) – and the interfaces between these mental structures and the conceptual system. These “specific unique building blocks for phonology, syntax, and their connection to concepts” are what makes language and language acquisition possible (Jackendoff 2007: 388f.).

This account of course has not mentioned important ecological factors (e.g. navigation, foraging, predator avoidance) that will have contributed to these developments and constructed niches in which these factors could develop further and faster. In the case of language, for example both “fast processing and mapping from hierarchical structure to temporal ordering,” which are two fundamentally important features of human language, “can be attributed to progresses in the timing of actions necessary for producing and using hand axes, [as well as throwing] that is, to sensomotoric skills that could have been adapted for language” (Wunderlich 2006). Support for this thesis comes from the fact that PET scans have shown a that there is neural circuitry supporting and involved in both language production and early stone age tool-making (Stout et al. 2008, see also here).

It also fits with our general model that there is mounting evidence “that much temporally sequenced hierarchical structure is constructed by the same part of the brain […] whether the material being assembled is language, dance, hand movements, or music (Jackendoff 2007: 388). Additional work on mirror neurons, motor neurons that activate both when an action is performed and observed (Rizzolatti & Craighero 2004), points in the direction that they are involved in understanding the goal-related actions of others in a social context. The evolution of a Mirror Neuron System for understanding actions and intentions may have been a crucial part of the cognitive development that made human thinking possible.

This is also supported by the fact that the human conceptual system has two distinctive properties: One the one hand it enables abstract, relational, role-governed, symbolic thinking (Penn et al. 2008). But at the same time human concepts are still deeply rooted in, based on, and grounded in embodied sensori-motor experience (Barsalou 1999, Gallese & Lakoff 2005). This holds even for linguistic concepts and metaphors, which have been shown to be partly grounded in embodied cognition (Lakoff & Johnson 1980). To get back to language, a final indicator of the connectedness of social interaction and parts of higher-order cognition comes from proposals that “neural circuits doing computations to control the hierarchy of goal-related actions were ‘exploited’ to serve the newly acquired function of language syntax” (Gallese 2007: 666).

Now that we have some theoretical proposals on crucial aspects of human uniqueness (although this list is far from being definitive and exclusive), we can see in how far they are borne out by the comparative and developmental data that is available.

References:

Aitchison, Jean. 1998. The Articulate Mammal. An Introduction to Psycholinguistics. London / New York: Routledge.

Barsalou, Lawrence W. 1999. “Perceptual Symbol Systems.” Behavioral and Brain Scienes 22.4: 577–609.

Bickerton, Derek (2009): Adams Tongue: How Humans Made Language. How Language Made Humans. New York: Hill and Wang.

Bühler, Karl (1934): Sprachtheorie: Die Darstellungsfunktion der Sprache. Stuttgart: Fischer.

Carruthers, Peter (2002), The cognitive functions of language, in: Behavioral and Brain Sciences, 25 (6),

657–726

Cassirer, Ernst (2006): An Essay on Man: An Introduction to a Philosophy of Human Culture. Hrsg. v. Maureen Lukay. Hamburg: Meiner (Gesammelte Werke. Hamburger Ausgabe. Band 23).

Cheney, Dorothy L. and Robert M. Seyfarth. (2007) Baboon Metaphysics: The Evolution of a Social Mind. Chicago: University of Chicago Press.

Clark, Herbert (1996): Use of Language. Cambridge: Cambridge University Press.

Deacon, Terrence William (1997). The Symbolic Species. The Co-evolution of Language and the Brain. New York / London: W.W. Norton.

Dunbar, R. I. M. and Susanne Shultz. (2007)“Evolution in the Social Brain” Science 317: 1344-1347

Evans, Vyvyan and Melanie Green (2006): Cognitive Linguistics: An Introduction. Edinburgh: Edinburgh University Press.

Fauconnier, Gilles and Mark Turner (2002) The Way We Think: Conceptual Blending and the Mind's Hidden Complexities. New York: Basic Books.

Fodor, Jerry A. (1998) Concepts. Where Cognitive Science Went Wrong. Oxford Congitive Science Series. Oxford: Clarendon.

Gallese, Vittorio (2007). Before and below 'theory of mind': Embodied simulation and the neural correlates of social cognition. Philosophical Transactions of the Royal Society B-Biological Sciences 362 (1480):659-669

Gallese Vittorio, Lakoff George (2005) The Brain’s Concepts: The Role of the Sensory-Motor System in Reason and Language. Cognitive Neuropsychology, , 22:455-479

Graumann, Carl F. (2002): Explicit and Implicit Perspectivity. In: Carl F. Graumann und Werner Kallmeyer (Eds): Perspective and Perspectivation in Discourse. Amsterdam, Philadelphia: John Benjamins Publishing Company, 25-40.

Harder, Peter (fc) Conceptual construal and social construction .

Hurford, James M. (2007): The Origins of Meaning: Language in the Light of Evolution. Oxford: Oxford University Press.

Jackendoff, Ray (2007): Linguistics in Cognitive Science: The State of the Art, The Linguistic Review 24, 347-401.

Lakoff, George, and Mark Johnson (1980) Metaphors we live by. Chicago: University of Chicago Press

Lewin, Roger (2005): Human Evolution: An Illustrated Introduction. Oxford: Blackwell.

Moll, Henrike, & Michael Tomasello. (2007) Co-operation and human cognition: The Vygotskian intelligence hypothesis. Philosophical Transactions of the Royal Society 362: 639-648.

Penn, Derek C, Keith J. Holyoak. and Daniel J. Povinelli (2008): Darwin's mistake: Explaining the discontinuity between human and nonhuman minds. In: Behavioral and Brain Sciences (31:2): 109-130.

Premack, David und Guy Woodruff (1978): Does the Chimpanzee have a

Theory of Mind? In: Behavioral and Bran Sciences 1: 515-526.

Reader, S.M. and K.N. Laland. 2002. “Social Intelligence, innovation, and enhanced brain size in primates” PNAS 99: 4436-4441.

Rizzolatti, Giacomo and Laila Craighero. “The Mirror-Neuron System.” Annual Review of Neuroscience 27 (2004): 169–192.

Searle, John R. (1995): The Construction of Social Reality. New York: Free

Press.

Sperber, Dan and Deirdre, Wilson (1995): Relevance: Communication and Cognition. Second Edition. Malden et al.: Blackwell.

Suddendorf, Thomas & Michael C. Corballis. (2007) The Evolution of Foresight: What is mental time travel, and is it unique to humans? Behavioral and Brain Sciences 30.3: 219-313.

Sterelny, Kim (2003): Thought in a Hostile World: The Evolution of Human Cognition. Malden u.a.: Blackwell.

Stout D., N. Toth , K. Schick, and T. Chaminade (2008): Neural correlates of Early Stone Age toolmaking: technology, language and cognition in human evolution. Proclamations of the Royal Society of London B: Biological. Sciences 363(1499):1939-49.

Tomasello, Michael (2003): Constructing A Language. A Usage-Based Approach. Cambridge, Massachusetts; London, England: Harvard University Press.

Tomasello, Michael (2008): The Origins of Human Communication. Cambridge, MA; London, England: MIT Press.

Tomasello, Michael, Malinda Carpenter, Josep Call, Tanya Behne, and Henrike Moll (2005): Understanding and Sharing Intentions: The Origins of Cultural Cognition. In: Behavioral and Brain Sciences 28:5, 675–691

Tuomela, Raimo (2007): The Philosophy of Sociality: From A Shared Point of View.

Oxford: Oxford University Press.

Tulving, E. 2005. Episodic memory and autonoesis: Uniquely human? In H. S. Terrace, & J. Metcalfe (Eds.), The Missing Link in Cognition (pp. 4-56). NewYork, NY: Oxford University Press.

Quine, Willard van Orman (1960): Word and Object. Cambridge, MA: MIT Press.

Verhagen, Arie (2007): Construal and Perspectivization. In: Dirk Geeraerts and Herbert Cuyckens (eds.) The Oxford Handbook of Cognitive Linguistics. Oxford: Oxford University Press.

Wunderlich, Dieter (2006): “What forced syntax to emerge?” In H.-M. Gärtner et al. (eds.) Between 40 and 60 puzzles for Krifka. ZAS Berlin

Altruism in Chimpanzees

Ed Yong has a nice post up on altruistic behaviour in chimps.

It is also worth it to check out some of his previous posts, such as:

Chimps console each other to reduce stress after fights

Cultured chimps pass on new traditions between groups

An Evolutionary Perspective on the Human Brain

This term I wrote an essay on the topic of human uniqueness from an evolutionary perspective. As I drew on research that is also relevant to this blog, (and to some extent has already been covered here). I'll post some of it here.
In this post I'll have a short look at the human brain from a neuroscientific, a comparative, and an evolutionary perspective:

Human Evolution

We are evolved primates. (As are all other primates of course. So maybe it is better to say that we, like all other primates, are evolved beings with a unique set of specializations, adaptations and features. )

In our lineage, we share a common ancestor with orangutans (about 15 million years ago (mya)), gorillas (about 10mya), and most recently, chimpanzees and bonobos (5 to 7 mya). We not only share a significant amount of DNA with our primate cousins, but also major anatomical features (Gazzaniga 2008: 51f., Lewinn 2005: 61) These include, for example, our basic skeletal anatomy, our facial muscles, or our fingernails (Lewin 2005: 218ff.).

What most distinguishes us as humans on an anatomical level are our bizarre hair distribution, our upright posture and the skeletal modifications necessary for it, including a propensity for endurance running, our opposable thumbs, fat deposits that are unusually extensive (Preuss 2004: 5), and an intestinal tract only 60% the size expected of primates our size (Gibbons 2007: 1558).

Finally, there is also a distinguishing feature that is a much more remarkable violation of expectations – a brain three times the size expected of a primate our size. This is all the more interesting as primates are already twice as encephalized as other mammals (Lewin 2005: 217). A direct comparison shows this difference in numbers: Whereas human brains have an average volume of 1251.8 cubic centimetres and weigh about 1300 gram, the brains of the other great apes only have an average volume of 316.7 cubic centimetres and weigh between 350-500 gram (Rilling 2006: 66, Preuss 2004: 8). In a human brain, there are approximately a hundred billion neurons, each of which is connected to about one thousand other neurons, comprising about one hundred trillion synaptic connections (Gazzaniga 2008: 291). If you would count all the connections in the napkin-sized cortex alone, you would be finished after 32 million years (Edelman 1992: 17).

Expensive Tissue

The human brain is also extremely “expensive tissue” (Aiello & Wheeler 1995): Although it only accounts for 2% of an adult’s body weight, it accounts for 20-25% of an adult’s resting oxygen and energy intake (Attwell & Laughlin 2001: 1143). In early life, the brain even makes up for up 60-70% of the body’s total energy requirements. A chimpanzee’s brain, in comparison, only consumes about 8-9% of its resting metabolism (Aiello & Wells 2002: 330). The human brain’s energy demands are about 8 to 10 times higher than those of skeletal muscles (Dunbar & Shultz 2007: 1344), and, in terms of energy consumption, it is equal to the rate of energy consumed by leg muscles of a marathon runner when running (Attwell & Laughlin 2001: 1143). In all, its consumption rate is only topped by the energy intake of the heart. (Dunbar & Shultz 2007: 1344).

Consequently, if we want to understand the evolutionary trajectory that led to human cognition there is the problem that “because the cost of maintaining a large brain is so great, it is intrinsically unlikely that large brains will evolve merely because they can. Large brains will evolve only when the selection factor in their favour is sufficient to overcome the steep cost gradient“ (Dunbar 1998: 179). We have to come up with a strong enough selection pressure operative in the Pleistocene environment of evolutionary adaptedness that would have allowed such “expensive tissue” to evolve (Bickerton 2009: 165f.).

What About the Brain is Uniquely Human?

If we look to the brain for possible hints, we first find that presently, there is “no good evidence that humans do, in fact, possess uniquely human cortical areas” (although the jury is still out) (Preuss 2004: 9). In addition, we find that there are functions specific to humans which are represented in areas homologous to areas of other primates. Instead, it seems that in the course of human evolution some of the areas of the brain expanded disproportionally, “especially higher-order cortical areas, including the prefrontal cortex” (Preuss 2004: 9, Deacon 1998: 435-438). This means that humans do not only think in a better way, but that they think differently (Preuss 2004: 7). The expansion and apparent specializations of only certain kinds of neuronal areas could indicate a qualitative shift in neuronal activity brought about by re-organization of existing features, leading to a wholly different style of cognition (Deacon 1998: 435-438 Rilling 2006: 75).

This scenario squares well with what we know about the way evolution works, namely that it always has to work with the raw materials that are available, and constantly co-opts and tinkers with existing structures, at times producing haphazard, cobbled-together, but functional results (Gould & Lewontin 1979, Gould & Vrba 1982). Given the relatively short time span for the evolution of the “most complex structure in the universe, we have to acknowledge how preciously little time the evolutionary process had for ‘debugging.’ It could well be that make the human mind so unique is that it is a imperfect ‘Kluge:’ a clumsy or inelegant – yet surprisingly effective – solution to a problem,” like the Apollo 13 CO2 filter or an on-the-spot invention by MacGyver (Marcus 2008: 3f.). It may thus well turn out that what we think makes us so special is a mental “oddity of our species’ way of understanding” the world around us (Povinelli & Vonk 2003: 160). It is reasonable then to assume that human cognition did not just simply get better across the board, but that instead we owe our unique style of thinking to quite specific specializations of the human mind.

With this in mind, we can now ask the question how these neurological differences must translate into psychological differences. But this is where the problem starts: Which features really distinguish us as humans and which are more derivative than others? A true candidate for what got uniquely human cognition off the ground has to pass this test and solve the problem how such “expensive tissue” could evolve in the first place.

References:

Aiello L.C. and P. Wheeler 1995. ”The expensive tissue hypothesis: the brain and the digestive system in human and primate evolution.” Current Anthropology 36:199–221

Aiello, Leslie C. and Jonathan C. K. Wells (2002): “Energetics and the Evolution of the Genus Homo.” In: Annual Review of Anthropology 31:323–38.

Attwell, David and Simon B. Laughlin. (2001.) “An Energy Budget for Signaling in the Grey Matter of the Brain.” Journal of Cerebral Blood Flow and Metabolism 21:1133–1145.

Bickerton, Derek (2009): Adams Tongue: How Humans Made Language. How Language Made Humans. New York: Hill and Wang.

Deacon, Terrence William (1997). The Symbolic Species. The Co-evolution of Language and the Brain. New York / London: W.W. Norton.

Dunbar, Robin I.M. (1998)“The Social Brain Hypothesis” Evolutionary Anthropology 6: 178-190.

Dunbar, R. I. M. and Susanne Shultz. (2007)“Evolution in the Social Brain” Science 317: 1344-1347

Edelman, Gerald Maurice (1992) Bright and Brilliant Fire: On the Matters of the Mind. New York: Basic Books

Gazzaniga, Michael S. (2008): Human: The Science of What Makes us Unique. New York: Harper-Collins.

Gibbons, Ann. (2007) “Food for Thought.” Science 316. 1558-1560.

Gould, Stephen Jay and Richard Lewontin (1979). "The spandrels of San Marco and the Panglossian paradigm: a critique of the adaptationist programme". Proclamations of the Royal. Society of London B: Biological Sciences 205 (1161): 581–98.

Gould, Stephen Jay, and Elizabeth S. Vrba (1982), "Exaptation — a missing term in the science of form," Paleobiology 8 (1): 4–15.

Lewin, Roger (2005): Human Evolution: An Illustrated Introduction. Oxford: Blackwell.

Marcus, Gary (2008): Kluge: The Haphazard Evolution of the Human Mind. London: Faber and Faber.

Povinelli, Daniel .J. and Jennifer Vonk. (2003) Chimpanzee minds: Suspiciously human? Trends in Cognitive Sciences, 7.4, 157–160.

Preuss Todd M. (2004): What is it like to be a human? In: Gazzaniga MS, editor. The Cognitive Neurosciences III, Third Edition. Cambridge, MA: MIT Press: 5-22

Rilling, James K. (2006.) “Human and NonHuman Primate Brains: Are They Allometrically Scaled Versions of the Same Design?” In: Evolutionary Anthropology 15: 67-77

Back to Blogging Soon

Today I handed in my last essay for this term and I really hope I'll be able to post more regularly now.

Meanhwile, both Neurophilosophy and Babel's Dawn have interesting posts up regarding work done by Ofer Tchernichovski, Olga Feher, and her colleagues regarding the tendency of birdsong to converge on the on the standard wildtype-model after a few generations when the first generation was isolate and had no model output they could adopt. (although I find it a bit misleading if birdsong is called language as is done over at the otherwise excellent blog Neurophilosopy)

This happened by small variations the birds made to their input over a couple of generations. These variations accumulated an in the end yielded the wild-type.

In the words of the authors:

"Thus, species-typical song culture can appear de novo. Our study has parallels with language change and evolution. In analogy to models in quantitative genetics, we model song culture as a multigenerational phenotype partly encoded genetically in an isolate founding population, influenced by environmental variables and taking multiple generations to emerge." (Feher et al. 2009).

The question now is inhowfar we can draw a parallel to how human language may be genetically encoded. The topic has been covered previously (here) and although there are also opposing views, (see, for example, Derek Bickerton here), it seems that a consensus is about to emerge that sees language acquisition as the interplay between social learning, innate biases, and more general cognitive capacities. (see, e.g. here and here)