PROPOSED: A SCIENTISTIC PERSPECTIVE ON EVERYTHING.
A POSSIBLE BASIS FOR IMPROVED COMMUNICATION IN A WORLD OF CHAOS AND INCOHERENCE.
PART TWO: LIFE, CONSCIOUSNESS AND HUMAN THOUGHT.
Domain 2. The necessary interaction of all living organisms with reality as it is (Reality) occurs through exquisitely precise physical, chemical and biological mechanisms that themselves are part of and harness the intrinsic ‘physical’ processes of Reality. Real or physical signals are recognized, internalized and processed in organized, interdependent, ‘intelligent’ biological systems (organisms) that respond to the environment, grow and multiply. This primary response to the environment can be recognized in all organisms, i.e. they appear to be ‘conscious’ of their environment. Animals have added prodigiously to this basic template: nervous systems and sense organs allow for a representational awareness of the internal and external world.
Let us start with what we all know well, our minds, and work backwards.
Embedded in our conscious minds lies a deep contradiction: we know it intimately, it is part of us yet we know very little about it. Mind is inexplicable even as everyone is utterly familiar with it: the greatest show on earth, the Magnificent Theater of The Mind, featuring true feeling, compelling narrative, cycloramic 3-D full color and stereophonic sound – even in our dreams as we sleep. Add to this our favorite tastes, smells and pleasurable activities; everything.
Despite this intimacy, perhaps because of it, we have always been confused about what and how it is and what it all means. There are many fanciful theories: an immaterial spirit that enters our body, an accurate representation of the external and internal world, our governing faculty, seat of the decider making choices, or even a completely pointless and distracting epiphenomenon of unconscious brain processes. Actually, the objective answer is disarmingly simple: Consciousness is everything an organism does in response to its environment, whether that includes thinking about it or not. The mechanisms by which our subjective experiences are produced are still shrouded in mystery. There is no adequate explanation, despite prodigious amounts of empirical data, because we still do not know all the structures that are involved. Invoking patterns of electrical discharges across trillions of synapses does not explain much. Our narratives are still pretty paltry.
Human self-aware consciousness, thought and language, along with their social implications, without doubt are amongst our most characteristic attributes. We are constantly aware of our feelings and our interactions with both the environment and our fellow sapient creatures, with an almost limitless ability to think, talk and write about it. We are compelled by our inner experiences and social interactions; it is there that we feel we find the reasons for our existence, our purpose and the meaning of it all. Many believe that this represents the essence of who and what we are. But in order to really understand what this means we need to examine the process, the underlying mechanics. After all, one would be very confused about the workings of a TV by analyzing the content of the programs on its screen. Rather, by unlocking the biological secrets of human thought we may be able to extend our self-understanding greatly, in turn, hopefully opening up opportunities for social improvement. Ignorance is not bliss.
Thus, if consciousness relates to the essence of who and what we are, it would be critically important to understand it. That would be a great step toward understanding ourselves and others. A good place to start, then, is to separate subjective content from the underlying objective physicochemical and biological, including psychological, processes.
We are not alone. Clearly, many other animals have easily recognizable consciousness since they objectively exhibit behaviors associated with consciousness – eating, drinking, sleeping, seeing, hearing, caring for off-spring, etc. Mammals and primates have sense organs just like ours with large brains and behaviors that parallel ours for the most part. Animals also exhibit on careful study what appears to be emotions, learning, memory, language and problem solving ability. The prior opinion that we were the only conscious creatures appears to have been based on prejudice and deep ignorance. Or, perhaps, we do not understand what our ancestors meant by consciousness In all likelihood, we will never fully know what it is like to be a bat, a lion, a dog, a dolphin or an ant. Each species represents their own very special case. We are constantly being amazed by how complex and intricate the lives of other creatures are. The closer we look the more common threads there are between all living creatures.
The Unity of Life
All animals capture and process ‘information’ from the environment in very similar ways. One of the major discoveries of evolutionary biology over the last 5 decades is the surprising degree to which all animals, down to the very simplest, share in a large set of common molecules that coordinate development and allow interaction with the environment. About 40% of the genes of a tiny worm, Caenorhabditis elegans, persist in humans. It has been possible to insert the human version back into the worm where it continued to perform its functions quite well. Outwardly, then, there is no similarity between this worm and a human being, but if one drills down on the molecular details, the correspondences are astounding. The similarities may even outweigh the differences. Human and worm have about the same number of protein coding genes, ~20,000, even though the human genome is about 30 times longer. But, by studying this little denizen of the dirt, we have learned a lot about ourselves. Certainly, we must accept the very likely possibility that any creature with neurons shares the beginnings of consciousness with us in some essential but not yet clearly identified way. Anyway, rejecting this possibility out of hand would be repeating a mistake we have often been guilty of in the past.
Let’s get to know this sightless little nematode a little better. C. elegans was first described by Emile Maupas in 1900. Then it was left mostly alone until 1960 when Sidney Brenner suggested that this humble, ~1 mm worm with no brain or respiratory and circulatory system would be ideal for intensive, collaborative study in the hope of understanding the mysteries of life. Brenner ultimately received a Nobel Prize in 2002. Today it is the best understood animal of all, including us. It was the first multi-cellular organism to have its genome sequenced. This little worm is also extremely predictable structurally: every one of 959 somatic cells of hermaphrodites has been mapped, including the structure and connections of each of its 302 neurons (males, a minority of the population, have 383):
“With only five olfactory neurons, C. elegans can dynamically respond to dozens of attractive and repellent ‘odors’ or ‘tastes’. Thermosensory neurons enable the nematode to remember its cultivation temperature and to track narrow isotherms. Polymodal sensory neurons detect a wide range of nociceptive cues and signal robust escape responses. Pairing of sensory stimuli leads to long-lived changes in behavior consistent with associative learning. Worms exhibit social behaviors and complex ultradian rhythms driven by calcium ion oscillators with clock-like properties. Genetic analysis has identified gene products required for nervous system function and elucidated the molecular and neural bases of behaviors.” [De Bono, 2005.]
When describing the behavior of a 1 mm blind roundworm, dispassionate scientific observers cannot avoid using anthropomorphic terms because the objective similarities to human activities are undeniable. Memory, learning, smell, rhythms, tracking, escape, social behavior and measurement of time; these terms describe intelligence and consciousness, not necessarily of the human kind, but of an organism fully engaged according to its needs and abilities in its world, sensing it, evaluating it, applying memory and making choices, using all available tools to flourish and survive. Lacking eyes it does not see, without ears it can not listen, BUT like the retina it has photoreceptors and like the cochlear membrane this little worm has mechanoreceptors. It does have an extremely rudimentary ‘nose’, and it does feed on bacteria so we can wonder what it likes best. There is neural circuitry for navigation and exploration to satisfy a natural curiosity perhaps.
Some populations of C. elegans feed in social groups, other populations consist of solitary individuals proceeding by themselves – a genetic basis for political preferences??. This is all due to the presence of a variant of one gene that codes for neuropeptide-y receptor. A related receptor is found throughout the animal kingdom and affects food consumption, mood and anxiety. Interestingly, it may modulate our intake of alcohol.
A small worm with no brain thus appears to be highly intelligent and clearly displays awareness of its surroundings – consciousness! (In fact, it is surprising how much can be done with so little.) This kind of anthropomorphizing (teleonomy) risks the introduction of confusing biases, but one has to start somewhere to gain insight and understanding of ourselves, others and the natural world. The complex and graceful interaction between a male C. elegans and an hermaphroditic partner is a choreography of multiple intricate steps that has to be perfectly sequenced for success: contact, reversing, finding the entrance, inserting spicules and ejaculation. This particular behavior (e-motion) is coordinated by oxytocin-like peptides (nematocin) without which the sequence becomes uncoordinated, ineffective and impotent. A few neurons are capable of producing very complex responses to the environment, responses that can be modulated and coordinated by chemicals.
If a short oligopeptide hormone can do this for a tiny worm with 302 neurons, imagine what it could do for an animal with millions or billions of neurons: oxytocin is a peptide consisting of 9 amino acids – not big enough to be called a protein – and it contributes much to what makes us human. It affects sexual, social and maternal behavior, controls lactation and uterine contraction; it can also affect levels of anxiety and fear, even ethnocentric behavior; the list is long and the interactions are extremely complicated. The cellular and tissue distribution of receptors for these neuropeptides varies widely among species and this has a profound effect on the many different types of behavior expressed by different animals, amongst closely related species, and even within a species such as C. elegans. It is complicated! With more basic information forthcoming, we are bound to learn much and our understanding of behavior should become even more nuanced. At this stage it seems that, while inputs and outputs are extremely variable, the internal tools with which responses are managed are surprisingly uniform. A stark, fundamental difference between worm and man is that the latter has a vast amount of DNA that is ‘non-functional’, i.e. DNA that we do not quite understand yet. [Bargmann, 2013. Wikipedia. Insel, 2010.]
Climbing further down the phylogenetic ladder in our search for what might be deemed unconscious life, let us take a quick peek at Paramecium, a unicellular creature with multiple nuclei. However, this one extremely large cell has many specialized intracellular organelles. There is a mouth area where food vesicles are ingested and then funneled through the cell as digestion takes place. Its cell membrane bears cilia for propulsion, is excitable and, like a neuron, can maintain a surface electrical charge due to the presence of ion channels. One cell thus performs many specialized functions. Its genome codes for about 40,000 proteins, almost double that of Homo. This is also, therefore, not a candidate for simple, unintelligent life. It is very complex, coordinated and extremely good at what it does. A Paramecium likely is more complex than any single mammalian cell. It performs many different specialized tasks and it is ‘conscious’ of its environment. It even has the ability to solve ‘simple’ navigation problems by ‘choosing’ between a few ‘simple’ strategies. Memory appears to be involved.
Bacteria occupy the bottom rung of life on the complexity scale, so what can these minute unicellular creatures do? Most of them amount to almost nothing, up to a million or more could fit inside a single Paramecium. However, once methods were developed to study their behavior and correlating such behavior with molecular structure, there ensued shocked surprise: “Nearly all motile bacteria can sense and respond to their surroundings—finding food, avoiding poisons, and targeting cells to infect, for example—through a process called chemotaxis” which exhibits “exquisite sensitivity, extensive dynamic range and precise adaptation”. [PhysOrg, 2012. Hazelbauer, 2008.]
Rich systems of communication via chemical signals can exist between individuals of the same or different strain, sometimes communicating with a different species or even the host. Thus bacteria can sense their population density, and so judge whether conditions are favorable or adverse (quorum sensing). This allows bacteria to coordinate their gene expression and the behavior of their entire community to enhance collective survival and prosperity. This may even entail a life-style switch, from a nomadic individual, “planktonic” existence to that of a strictly controlled community, e.g. a biofilm, one that is relatively impervious to toxins, or to a virulent community that can attack other organisms or their host. In biofilms it has been found “that the descendants could remember the surface sensing signals of their ancestors”, suggesting primordial memory and learning. This is surprising. Also quite impressive has been the discovery of electrical signaling resembling neuronal activity, allowing different parts of the biofilm to communicate. [Lee, CK et al. 2018, Prindle, A et al. 2015, Masi,E et al. 2015]
There seems to be no limit to the strange behaviors of bacteria; strange because such behavior seems, improbably, to be an analogue of human behavior. For example, there is community policing of ‘cheaters’ that benefit from collective efforts but do not contribute their part. In some situations, some cheating is tolerated, apparently because such diversity improve chances of overall survival. Sometimes competing entities might try to disrupt the cooperative efforts of others by chemically interfering with their signals. Bacteria are actually engaged in a never-ending arms-race with intense and lethal competition for lebensraum and natural resources! (Humans can benefit from this because bacteria are the major pathway for introducing non-carbon elements into the food chain.) Bacteria thus have a very impressive arsenal of toxins and weapons at their disposal, even leading to feasting on DNA released during the fray. A recent sensational headline warned “Killer Cholera Bacterium Stabs Others With Tiny Spear, Steals DNA” – some fragments of victims’ DNA may become incorporated in the genome of the victors in the hope of promoting fitness for survival. Sometimes fratricidal groups will kill off their non-aggressive comrades, but the opposite can also happen: virulent individuals commit suicide when exposed to the ‘love-hormones’ of their more peaceful kin – give me freedom, or give me death. [Speaker Abstracts, 5th ASM Conference on cell-cell communication, 2014.]
Bacteria are the smallest free-living units of DNA – viruses exist at the borderline of life. While animals are infinitely more complex, bacteria are definitely not simple. There are predictions now being made that we will never be able to accurately conceptualize the submicroscopic structure and inner workings of even a single cell. Therefore, it seems rather odd to call something simple when one is utterly unable to explain how it works. That almost everyone is guilty of ignoring this paradox raises interesting questions about the accuracy and precision of human thought: maybe close is good enough? Now that we are able to study bacteria with more sophisticated tools we have been surprised at their level of complexity and exquisite interaction with their environments. This now makes sense given the fact that life and its precursors have been incubating for ~4 billion years or more. Today’s survivors are all highly evolved and maximally complex, it being highly unlikely that a bacterium from the dawn of life could survive today.
Nobody would seriously suggest that bacteria think the way we do. However, careful observation of them leads to the firm conclusion that they are very ‘intelligent’, conscious in an operational and objective sense of the word, and that they react purposefully. It is apparently built into their DNA, or, more precisely, that is what DNA does. Understanding what exactly that purpose is and how it is pursued is still a deep and fascinating mystery. A better intuitive understanding of what drives molecules would be very helpful. DNA is a very talented, purpose driven and intelligent molecule indeed! In its most basic bacterial form, it has managed to infiltrate and populate every nook and cranny where life could survive.
A common thread in human history seems to be that we always have been and continue to be surprised by Reality. Now that oracles have been proven unreliable or possibly deceitful as sources of knowledge regarding the nature of reality, all possibilities are now on the table. We should continue to expect more surprises.
After learning of the extraordinary ‘intelligence’ of bacteria, worms, fruit flies, fish and so on, we come face to face with a very interesting and revealing set of questions: what a piece of work is man? How do we do what we do? But most important, perhaps, what, exactly, are we doing, and why? One of the first attempts at a science based materialist investigation of these matters was apparently met with anger and derision. Edward O. Wilson has said that he was taken completely by surprise by the reaction to his “Sociobiology, The New Synthesis” published in 1975. Political biases came into play. However, answers to our basic questions about life are seemingly far more subtle and complex than what we had anticipated. Our universe contains much more intelligence than we ever imagined. But how does this help us in dealing with our apparently chaotic culture? That is our fundamental challenge. It has been said that ignorance is bliss. However, our thesis is that ignorance is also very dangerous – it certainly has been so far.
From what we now know, it seems clear that all of life exhibits a form of intelligence by directly responding to and interacting with its environment, even altering that environment in a particular niche of Reality. We will call this biophysical consciousness. It has been stated that most or all animals also exhibit phenomenal awareness which would be in addition to the various forms of basic biophysical awareness. That is, most animals are also aware of macroscopic structures and events in their environment – the crash of a falling tree, a sudden flash of lightning or the repellent stench of rotting flesh (repellent to us but attractive to flies). Thus through enhanced processing and integration of the basic physical signals that give rise to biophysical consciousness many animals have senses like ours; sight smell, sound, vision, touch, etc. It seems almost certain that animals with bodies like ours (eyes, ears, noses, tongues and brains, etc.) would experience the world generally in the way we do, but with numerous specific differences. For example, most primates have trichromatic color vision – they can see red. Most other mammals are dichromatic and can not see red. Shapes, sizes and movements seem to be observed similarly to us, but we can not even imagine what their sense of smell or taste is like, or what they feel when threatened or in danger. Trying to imagine the world of very different creatures like fish, worms and bacteria at this time is asking too much. (Since there is also a wide variation in how humans are constituted, we are also never quite sure what another person would be experiencing.)
Furthermore, as an example, it is still a profound mystery as to how the utterly reliable and predictable subjective sensation of any color comes about – the qualium of color. Apparently, we can distinguish ~200,000 shades of color. It is another one of those ‘miracles’. Add to this the stunning variety of tastes, smells, sounds and feelings that we experience, pleasurable and otherwise, and we can not help but being cognitively overwhelmed. Apparently, the nervous systems processes signals from everywhere in the body in a complex hierarchical system, feeding information via the autonomic and peripheral systems upwards through the hind-, mid- and forebrain. It then seems as if there is a cortical network that looks at all the intracranial activity and then produces a report to a separately experienced self. The dimensions of what is happening as we laugh, cry and dream are practically infinite: billions of neurons, trillions of synapses, interactions with peptides, hormones and the immune system, ad infinitum. But, put it all together and there effortlessly appears before us a clear and distinct world. It is quite beguiling, another miracle.
We have learned much about human consciousness by studying animals. Parallels with primates and mammals are now obvious. Somewhat surprising, it has also been very revealing to learn that fruit flies, fish and many other lower animals also use social strategies that can be correlated in humans: strategic copying, innovation, social learning. (Laland, KN. 2017) With new technologies we are now also learning much by scientifically studying human subjects. Research over the last few decades in human consciousness has yielded quite surprising results, leading to a complete rethinking of how it works and what its biological correlations are.
The almost universal assumption that what you see is what you get is not tenable anymore. The longstanding, still popular, common sense view that “the conscious self is fully in charge of behavior, sees the world generally as it is, and directs behavior as it sees fit” has been almost completely revised based on human psychological research. In essence, close observation of humans under controlled conditions has revealed that our mental processes may produce unreliable results unbeknownst to ourselves: our explanations of our own behavior are often not very rigorous at all; rather, the most convenient or facile reason may be selected from a trove of stock explanations, especially if it is socially acceptable. Actions may already be underway before conscious thought joins in, even though we might still think that we are consciously initiating the process. Gaps in a narrative or pattern may be unconsciously filled in. Conscious analysis may not even be essential for complex planning; goals and social motives can be activated in the absence of a conscious decision. There are therefore multiple extraordinary complex processes occurring while we are under the impression that a ‘simple’ conscious act is underway.
Perhaps the most arresting feature of all the new information about consciousness is that we have historically neglected the role of affect, feelings, mood and emotions in our lives – swept under the rug, as it were, because, quite simply, emotions were beyond the reach of all rational understanding. They needed to be suppressed or controlled, certainly banished from rigorous intellectual, scientific or philosophical discourse. Unlike intentional cognition, there is nothing clear and distinct about affect, yet here may lie another great store of future discovery and understanding. Emotions appear to provide the underpinnings of all our behavior, even ‘rational’ thought.
We know guilt, shame, fear, disgust, anger, hate, etc. These negative emotions tend to narrow the focus onto a problem to the exclusion of everything else. They often end in separation, loss, destruction or worse. Positive emotions may be less conspicuous or salient; they broaden and build, bring growth and innovation with improvements in health, wealth and happiness. Given our state of ignorance, we do not know how to best harness the powers within. The range of possibilities beckon, especially if it turns out that emotions are not as automatic and primitive as had been thought. (Barret, LF. 2017)
The adaptive value of human thinking and communication thus far appears centered primarily around social goals such as inclusion, cohesion, security and survival. Our interests in philosophy and science, i.e. pursuit of reliable and useful knowledge, are rather recent and had been largely secondary. This now appears to have changed, with science, technology and engineering affecting human social existence radically. These findings, accumulating now for a couple of decades, have been devastating to the classical conceit that consciousness controls input and output from the perspective of objective knowledge. The concept of humans as independent rational conscious executive agents is rarely true, if ever. [Baumeister et al, 2010. Panksepp, The affective brain and core consciousness, 2008.]
What have we learned then, so far, about human consciousness that is likely to be true? Well, as we already know, humans occupy a special place amongst the animals when it comes to thinking, language and complex social interaction. However, our consciousness, like all others, has evolved from basic biophysical consciousness over billions of years. It is an attribute of our particular biological heritage. At least all animals with brains have what is referred to as phenomenal consciousness; awareness of the structures and events in their surroundings through sense organs leading to highly intelligent responses, e.g. tracking a smell across an open field, identifying the prey and then capturing it. Humans can do much the same, except for the tracking of a smell part, but what no other animal can do is to communally identify a goal, devise a specific strategy, communicate it amongst the group, assign different responsibilities and then execute based on the mutual understanding of the articulated plan. Non-humans are at a deep existential disadvantage in this theater of operations! Each human can mentally simulate what is being discussed as if it were really happening. No other animal can communicate in complex logical sentences because none can think in such sentences. So their powers of simulation have to be very limited compared to ours. That, at least, is what the latest evidence suggests, but it is likely that animals will again surprise us to the upside.
We have diverged from other animals by virtue of this ‘quantum leap’: our ability to simulate events and circumstances away from the here and now, to communicate what is in our mind, and attempt to emulate what someone else is simulating in their mind based on their words. Past or future events can be simulated, shared, discussed and analyzed, leading to vastly improved cooperation, execution and coexistence. Such advanced teamwork obviously has been of great adaptive and survival value – fitness in our case is determined by how much information is processed, communicated and stored. We have access to a total store of about 200,000 words, the average person has a vocabulary of about 20,000 words, with an upper limit of about 100,000. We all have quite a memory for words, but there are extraordinary individuals, for instance, that can remember every day of their life. There are others that can remember a sequence of about 80,000 random digits. There are yet others that can replay a piece of piano music after hearing it once.
Nevertheless, notwithstanding the unreliabilities already mentioned, conscious thought has a creative ability of coming up with novel situations and ideas, including the ability to imagine, fantasize and speculate without limit or regard for practicality. These are the skills that produce art, literature, music or play-acting for entertainment and enlightenment. There are, also, real strengths inherent in our focused thinking: many individuals are able to intensely concentrate on logic, evidence and innovation, achieving very impressive results in technology, science, mathematics and philosophy. Our greatest creative achievements have been thus inspired, but also some of our worst misadventures. This creativity is the source of our celebrated faculty of so-called ‘free will’; mind can seemingly go anywhere. A garden of both good and evil is enclosed within the walls of our skull.
The evidence alluded to so far exposes numerous, unsuspected large gaps in our understanding of human and animal consciousness. Interestingly, while human consciousness is rightly elevated on a pedestal, much of what we know is based on studies in animals, including primates, rodents, insects, worms and bacteria. The evidence so far does not support the popular but ancient concept of a specific supra-natural or extraneous human faculty inserting itself into our bodies. All of the vegetative, tropic and reflexive functions, as well as many of their molecular and genetic underpinnings, present in humans, can be found in other animals. Our unique specializations, such as complex language and socio-cultural interactions, are very exceptional indeed but their primordial beginnings can be recognized in other animals. All this correlates very well with our large neocortex, great number of neurons and possibly 100 trillion synapses that are further fine tuned by physiological factors. Therefore, no unbridgeable gap or irreducible mystery appears to exist – our biological equipment seems very much to be up to the task. Our perplexity and confusion is due to the extraordinary nature of our subjective experiences, which had led many to assume a divine gift. However, it now seems likely that mammals also see, hear and taste like we do. They too have phenomenal consciousness, but, unlike us, they probably just don’t think or talk about it as much or as clearly as we do. Like many other mysteries, we can not explain phenomenal consciousness yet – it is extraordinarily complex, another ‘miracle’. Evidence based theories are only now beginning to show up.
In summary, consciousness divides the universe of information into two: the little that we are aware of and the rest that we are not. Protagoras had said something similar, “Of all things the measure is Man, of the things that are, that they are, and of the things that are not, that they are not”. Consciousness is a fundamental feature of life, itself having been produced by the dynamic natural processes of a submicroscopic and cosmic Reality. All species have their unique qualities. Our unique human mind appears to be a culmination of the ancient processes of biophysical awareness and phenomenal consciousness. Most of our processing of vast amounts of information still occurs in the biophysical realm without involvement of phenomenal or conscious thought (mind) centers. Everything that we find interesting is addressed in the realm of thought and simulation, and it becomes part of our culture when it is socially shared in words, sounds, images, tastes and artifacts. Our responses to information that we acquire from the environment (culture), however, are usually and mostly managed through automatic and semi-automatic processes residing in biophysical and phenomenal consciousness. Affect, emotions and feelings are central to our humanity, and, unsurprisingly, we understand even less about their role in our personal lives. It appears that conscious thought is very selective in its involvement in day to day operations, monitoring our activities and intruding when necessary. Intense focus and concentration on certain selected tasks are possible.
Human consciousness is, therefore, an extraordinary complex incarnation of biophysical and phenomenological awareness. Still, it is, in theory, potentially explainable by the underlying biological processes. Human behavior now might seem limitless and it had been easy to dismiss less complex organisms as unconscious machines or automatons, as some scientists and philosophers still do. That clearly is a mistake and it appears to be a vestige of prior ignorance. We have been blinded by the infinitely complex and utterly compelling nature of our subjective social and cultural experiences, erroneously concluding that lower animals can not possibly share anything like this with us; mythical narratives have also contributed to this prejudicial attitude. This represents a still very prevalent basic anthropocentric error.
Published 2015. Revised 2018.