Subjective-objective dichotomy

The subjective–objective dichotomy, a longstanding philosophical topic, is concerned with the analysis of human experience, and of what within experience is "subjective" and what is "objective." The dichotomy arises from the premise that the world consists of objects (entities) which are perceived or otherwise presumed to exist as entities, by subjects (observers). This division of experience results in questions regarding how subjects relate to objects. An important sub-topic is the question of how our own mind relates to other minds, and how to treat the "radical difference that holds between our access to our own experience and our access to the experience of all other human beings", known as the epistemological problem of other minds.

The subjective–objective dichotomy can be discussed from two standpoints. First is the question of "what" is known. The field of ontology deals with questions concerning what entities exist or can be said to exist, and how such entities can be grouped, related within a hierarchy, and subdivided according to similarities and differences. The second standpoint is that of "how" does one know what one knows. The field of epistemology questions what knowledge is, how it is acquired, and to what extent it is possible for a given entity to be known. It includes both subjects and objects.

Subjective-objective dichotomy

The world "out there" is perceived by the mind, and so also is the interior world of conscious events. The relation between the two is much debated:

"There is a common philosophical tendency...to conceive of the realm of belief and attitude as clearly distinct from the world of objects and events. This separation is typically presented in terms of a distinction between subjective and objective ..." —J. E. Malpas: Donald Davidson and the Mirror of Meaning: Holism, Truth, Interpretation, p. 192

"We consciously experience many different things, and we can think about the things that we experience. But it is not so easy to experience or think about consciousness itself...Does the world have an observer-independent existence (realism) or does its existence depend in some way on the operation of our own minds (idealism)? Is knowledge of the world 'public' and 'objective', and knowledge of our own experience 'private' and 'subjective'?" —Max Velmans: Understanding Consciousness, p. 3

"It is as if the brain has to impose a pattern of its own, even if there is no objective pattern present." —Oliver Sacks: Musicophilia: Tales of Music and the Brain, p. 265

"Every act of perception is to some degree an act of creation" —Gerald Maurice Edelman: Building a picture of the brain in "The Brain", p. 55

"It is well known that one sees with the brain rather than with the eye, and thus the brain tends to 'see' the familiar and expected." —Paul Craddock: Scientific investigation of copies, fakes and forgeries, pp.22, 23

"For the eye sees only what the mind is prepared to comprehend." —Robertson Davies: Tempest-Tost, p. 107

A very literal application of these last two quotations is studied in the subject of inattentional blindness. Another phenomenon related to the last quotation is the idée fixe. The role of our theories about the objective world in conditioning our subjective response and vice versa suggests that the subject, the I, is not localized to the individual but is partly to be found in the society in which the individual is immersed, and that portion of the society to which the individual is exposed.

The objective aspects of experience often are considered to lie within the domain of science. Science has practical impact upon technology and our understanding of interconnections. However, there are areas where science so far has had little impact. So there exists a difference in optimism about science, with one view opining that science will gradually extend to everything, and the opposite view opining that won't happen. For example, the statement is found in many books:

"...consciousness is a biological process that will eventually be explained in terms of molecular signaling pathways used by interacting populations of nerve cells.." —Eric R. Kandel: In Search of Memory: The Emergence of a New Science of Mind

This approach is the foundation of the 'blue brain' project, an effort to create a synthetic brain by reverse-engineering the mammalian brain. On the other hand, a contrary view is that aspects of mind are inherently subjective, and lie outside the reach of a scientific approach based upon objective observation by a detached observer:

"Epistemically, the mind is determined by mental states, which are accessible in First-Person Perspective. In contrast, the brain, as characterized by neuronal states, can be accessed in Third-Person Perspective. The Third-Person Perspective focuses on other persons and thus on the neuronal states of others' brains while excluding the own brain. In contrast, the First-Person Perspective could potentially provide epistemic access to own brain...However, the First-Person Perspective provides access only to the own mental states but not to the own brain and its neuronal states...Accordingly, one might speak of an 'epistemic mind problem'." —Georg Northoff: Philosophy of the Brain: The Brain Problem, pp. 2-3

One set of difficulties facing an objective study of subjective phenomena are summed up in the easy problem of consciousness and the hard problem of consciousness:

"What we do not understand is the hard problem of consciousness—the mystery of how neural activity gives rise to subjective experience. Crick and Koch have argued that once we solve the easy problem of consciousness, the unity of consciousness, we will be able to manipulate those neural systems experimentally to solve the hard problem." —Eric Kandel: In Search of Memory: The Emergence of a New Science of Mind, p. 382

The subjective aspects of science extend beyond the "hard problem", however. The formulation of a scientific theory is a mental process, not simply a matter of observation, although observation is involved. This realization takes the subjective-objective distinction to a more general level than arguments over the prospects of success in bringing certain areas of experience within the grasp of science.

For example, a statement of a scientific theory could take the form: All events p are determined by other events P . In order to be consistent with science today, and avoid oversimplification, one has to be very clear about how the events (p, P) are defined. One also has to replace "determined" by something like "logically imply".

"a theory is deterministic if, and only if, given its state variables for some initial period, the theory logically determines a unique set of values for those variables for any other period." —Ernest Nagel: Alternative descriptions of physical state

This quote indicates the need for great care in defining "events" and what is meant by "determined". Their meaning involves detailed descriptions of what constitutes an "event" and how one is said to "determine" another. A Popper-like view emerges with an "event" as some kind of formalized "state" and the relationship "determines" phrased as a "logical implication" of connection between states, all combined as parts of one or another abstract theory. That formalization puts a lot of emphasis upon mental constructions. From the stance of a Duhem, or a Popper, or a Hawking, the use of an intermediary, elaborate mental construction is a meld of the subjective and objective. It is used to determine connections about objective events, but the form of the theoretical construct is a product of subjective activities, and its particular form may well be more about the brain than anything else. Perhaps some aspects of the universe's operation can be expressed in terms of mental constructs in an analogy with the expression of a computer algorithm in terms of assembly language instructions peculiar to a particular computer, a translation of the algorithm into specific tiny steps that particular computer can handle, .

Lest this apparatus be thought of as an entirely formal understanding, some among us actually do have an intuitive grasp of these creative abstractions, perhaps analogous to the fact that some among us hear music in ambient sounds. Quoting Feynman about his creative process:

"It is impossible to differentiate the symbols from the thing; but it is very visual. It is hard to believe it, but I see these things not as mathematical expressions but a mixture of a mathematical expression wrapped into and around, in a vague way, around the object. So I see all the time visual things associated with what I am trying to do." —Richard P. Feyman: As quoted by Schweber: QED and the men who made it: Dyson, Feynman, Schwinger, and Tomonaga

This comment could be paralleled by others about the intuitions of musicians and mathematicians. The point is that the creation of scientific theories is subjective, and the very concepts of determinism are themselves subjective and mutable creations of the human mind. What is in charge here: the intuition conceiving the theory, or the theory that results; or is it an unending back-and-forth spiral from one to the other? The development of a theory is something of a bootstrapping process that might never converge.

"When stated at a general level, the subjective/objective dichotomy is recognized by most social scientists as one of the enduring metatheoretical dilemmas in the social sciences..." —David Swartz: Culture and Power: The Sociology of Pierre Bourdieu, p. 55

Our theories about the world are mental constructions, so we have a hen-and-egg problem trying to figure out if our theories work for describing our mental life:

"It is not possible to resolve which of the subjective or physical universes ultimately contains the other." —Alec Rogers: Cognitive Set Theory, p. 85

A rather different aspect of the subjective-objective divide is the role of social inhibition, a factor at work from the times of the Roman Inquisition and Galileo to the Scopes trial and Kennewick Man. A more recent concern is the structure of the educational system and the control over financing of research. There is a concern about the intrusion of societal elements into what is supposed to be an objective matter.

The exact opposite to this worry about the subjective coloring the objective, is the contrary worry that the language and practice of science is squeezing out the subjective aspects of experience:

"Through logic, the mind organizes itself and the data brought to it by scientific observation...The intellect — logic and its manifestations in language — has nothing whatever to do with happiness, the perfection of the self, the experience of the meaning of life, or man's relationship to absolute reality — God." —Jacob Needleman: The Heart of Philosophy, p. 210

One aspect of this concern over undervaluing the subjective is debate over the basis for moral responsibility and its connection with free will, for example, the dilemma of determinism.

Subjective-objective correlations

See also: Qualia and Behavioral neurology

Some subjective personal experiences have aspects that fall squarely into the realm of objective fact, and have implications that can be objectively verified. In some instances, it is debatable as to which is the epiphenomenon, the subjective event or its observable correlate. For example, there is debate over whether the placebo effect indicates a mental influence over the body.

An example is the experience of pain, an entirely subjective matter, but one that sometimes (but not invariably) can be related to the objectively observable operation of receptors, communication channels and brain activity. The consequence is that the subjective sense of pain is sometimes empirically connected to observable events, but the fundamental experience of pain itself is subjective. Other examples are addiction and psychological disorders. Besides the subjective aspects, one may discuss the mechanisms connecting subjective experiences and objective observables, and the role of programming upon these connections, such as psychiatric treatment, behavioral conditioning, and evolutionary limits.

As technology advances, the ability of humans to detect what is happening around them advances. This progress in observational technique extends to the brain and possibly the mind, and to our perceptive abilities. An example is the use of the PET scan in observing correlations between addiction and dopamine activity in the brain.

"Most PET (Positron Emission Tomography) studies of drug addiction have concentrated on the brain dopamine (DA) system, since this is considered to be the neurotransmitter system through which most drugs of abuse exert their reinforcing effects. A reinforcer is operationally defined as an event that increases the probability of a subsequent response, and drugs of abuse are considered to be much stronger reinforcers than natural reinforcers (e.g. sex and food). The brain DA system also regulates motivation and drive for everyday activities. These imaging studies have revealed that acute and chronic drug consumption have different effects on proteins involved involved in DA synaptic transmission. ... chronic drug consumption results in marked decrease in DA activity which persists months after detoxification and which is associated with deregulation of frontal brain regions." —Nora D Volkow, Joanna S Fowler, and Gene-Jack Wang: The addicted human brain: insights from imaging studies, p. 1061

These advances in observational technique require associated interpretation and theoretical models that explain what the observations mean. For example, when Galileo advanced the use of the telescope to observe the moons of Jupiter, skeptics doubted that the telescope actually showed reality. This old example only scratches the surface of relating scientific instruments to reality. After all, one could extrapolate from mundane terrestrial uses of the telescope, where its veracity could be directly examined, to more distant objects like Jupiter. The introduction of the microscope had a similar struggle for acceptance. Today however, only a few among us can understand the complexity of observations made with the hadron collider, and we rely upon certification by carefully selected experts. The importance of extremely technical theory in the experts' interpretation is obvious to all, and these theories, while supported by experimental observation, are products of the human subjective imagination.

To what extent our mental creations are limited by the innate functioning of our brain/nervous system (what might be called our "factory settings") and to what extent they mirror the real world is discussed in the field of psychological nativism, and is connected with the philosophers Kant, Schopenhauer, Popper, Chomsky, Pinker, Hawking and others.

The subjective aspect of scientific theories has led to a need to assess theories, to be able to choose one theory as preferable to another without introducing cognitive bias. Over the years, several criteria have been proposed.

1. It is elegant (Formal elegance; no ad hoc modifications)
2. Contains few arbitrary or adjustable elements (Simplicity/Parsimony)
3. Agrees with and explains all existing observations (Unificatory/Explanatory power)
4. Makes detailed predictions about future observations that can disprove or falsify the model if they are not borne out.
5. Boldness/fruitfulness: a theory's seminality in suggesting future work.

The falsifiability item on the list is related to the criterion proposed by Popper:

"It must be possible for an empirical scientific system to be refuted by experience." "Those among us who are unwilling to expose their ideas to the hazard of refutation do not take part in the game of science." —Karl Popper: The logic of scientific discovery, p. 18 and p. 280

About his choice of criteria, Kuhn says: "What, I ask to begin with, are the characteristics of a good scientific theory? Among a number of quite usual answers I select five, not because they are exhaustive, but because they are individually important and collectively sufficiently varied to indicate what is at stake." Colyvan says: "I do not claim that this list is comprehensive nor do I claim that it is minimal." Stephen Hawking supports items 1-4, but does not mention fruitfulness.

The goal here is to make the choice between theories less arbitrary. Nonetheless, these criteria contain subjective elements, and are heuristics rather than part of scientific method. Such criteria may not prove definitive in selecting a theory because the criteria sometimes conflict and different people will weight them differently. It also is debatable whether existing scientific theories satisfy all these criteria, and they may represent goals not yet achieved, a set of "New Year's resolutions", if you like. For example, Item 3: explanatory power over all existing observations, is satisfied by no one theory at the moment.

“Whatever might be the ultimate goals of some scientists, science, as it is currently practiced, depends on multiple overlapping descriptions of the world, each of which has a domain of applicability. In some cases this domain is very large, but in others quite small.” —E.B. Davies: Epistemological pluralism, p. 4 The desiderata of a "good" theory have been debated for centuries, going back perhaps even earlier than Occam's razor, which often is taken as an attribute of a good theory. Occam's razor might fall under the heading of "elegance", the first item on the list, but too zealous an application was cautioned by Einstein: "Everything should be made as simple as possible, but no simpler." Thomas Kuhn argued that changes in scientists' views of reality not only contain subjective elements, but result from group dynamics, "revolutions" in scientific practice and changes in "paradigms". As an example, Kuhn suggested that the Sun-centric Copernican "revolution" replaced the Earth-centric views of Ptolemy not because of empirical failures, but because of a new "paradigm" that exerted control over what scientists felt to be the more fruitful way to pursue their goals (Colyvan's requirement of "fruitfulness"). Whatever criteria one adopts for a 'good' theory, Worrall says the question of an objective algorithm for theory choice at the moment leaves open the question of what exactly it is rational or irrational to do. "One reason is that these criteria do not supply a choice algorithm is that in live cases of theory choice, and particularly during scientific revolutions, these different criteria seldom, if ever, tell in the same direction." In other words, although these criteria assist in identifying a 'good' theory, the selection among theories still is a subjective matter that will lead to different choices depending upon who is the judge. The environment of scientific practice has been described as involving these principles, which include some hypothetical and subjective aspects of science: The reality principle; We have to content ourselves with "things-as-they-appear", not 'reality'. The fact principle; Facts are not theory-neutral. Observation is not possible without reference to a theory. The theory principle; The process of abstraction from facts to theories is complex and intuitive, and any approach is valid if it leads to a theory that works. The testability principle; A scientific theory should be testable through reference to facts, although tests are rarely decisive. The veracity principle; Acceptance of a theory involves many factors: simplicity, efficacy, utility, explanatory power and human measures such as beauty. The Copernican principle; The universe is not organized for our benefit and we are not uniquely privileged observers. Complementary descriptions The subjective and objective correlates of some phenomena (like addiction or mental disorder) actually might describe the same phenomena from distinct perspectives; in other words, they might be complementary views: ...for each individual there is one 'mental life' but two ways of knowing it: first-person knowledge and third-person knowledge. From a first-person perspective conscious experiences appear causally effective. From a third person perspective the same causal sequence can be explained in neural terms. It is not the case that the view from one perspective is right and the other wrong. These perspectives are complementary. The differences between how things appear from a first-person versus a third-person perspective has to do with differences in the observational arrangements (the means by which a subject and an external observer access the subject's mental processes)." —Max Velmans: How could conscious experiences affect brains?, p. 11 Niels Bohr also believed there were differences between first-person and third-person perspectives, an outgrowth of his experience in atomic physics. However, in his view the two descriptions are irreconcilable because of the disturbance of the subject's first-person mental state by the third-person's act of observation itself: "...On the contrary, the recognition of the limitation of mechanical concepts in atomic physics would rather seem suited to conciliate the apparently contrasting viewpoints of physiology [that is, neuroscience] and psychology [mental phenomena]. Indeed, the necessity of considering the interaction between the measuring instruments and the object under investigation in atomic mechanics exhibits a close analogy to the peculiar difficulties in psychological analysis arising from the fact that the mental content is invariably altered when the attention is concentrated on any special feature of it." —Niels Bohr: Light and Life Some weak indirect support for this analogy is found in observations of the neural correlates of mental states: "...it is important to be clear about exactly what experience one wants one's subjects to introspect. Of course, explaining to subjects exactly what the experimenter wants them to experience can bring its own problems–...instructions to attend to a particular internally generated experience can easily alter both the timing and he content of that experience and even whether or not it is consciously experienced at all." —Susan Pockett: The neuroscience of movement In early philosophy The question of what is objective and what is subjective, and whether one or the other is more "real" has been a topic of philosophy since its earliest days. In Western philosophy it can be found in Plato, who considered our perceptions to be mere approximations to the world of ideal Forms, in the way that circles we encounter in nature are mere approximations to the ideal circle. The world of Forms was accessible only by the mind, not the senses. Contrary views were held by Aristotle, who would hold the "ideal" circle is only an abstraction from its many real-world examples, and without those examples the ideal circle simply would not exist. See this discussion about "instantiation". These two views of how the concepts of the mind relate to the perception of the world resurface again and again in later centuries, rephrased in novel terminologies. Some of these later treatments of the subject-object relationship were tied to theological issues. A not-so-serious example is the formulation of George Berkeley (1685-1753), who posed the famous question: "Does a tree fall in the forest when no-one can hear it fall?" He proposed that objects exist only when perceived by a conscious being, and to avoid the absurdities of this view posited that because God was omnipresent, things existed because they were in His consciousness. There once was a man who said 'God Must think it exceedingly odd   If he finds that this tree   Continues to be When there's no one about in the Quad.' Dear Sir: Your astonishment's odd: I am always about in the Quad.   And that's why the tree   Will continue to be Since observed by yours faithfully, God. —Twentieth century limerick quoted by Nigel Warburton: A Little History of Philosophy, p. 91 His view is summarized in the Latin phrase: Esse est percipi, to be is to be perceived. According to a famous anecdote, Samuel Johnson responded to Berkeley's views by kicking a stone and saying 'I refute it thus.'. One might argue that Johnson's experiment proves Berkeley's point: the stone exists because kicking it intruded the stone into Johnson's conscious awareness. In any event, Berkeley is correct within the interpretation that all we can know of reality is our perceptions of it. In 18th and 19th century philosophy To say it simply, Immanuel Kant (1724-1804) pointed out that we all shape our experience of things through the filter of our mind. The mind shapes that experience, and among other things, Kant believed the concepts of space and time were programmed into the human brain, as was the notion of cause and effect. We never have direct experience of things, the noumenal world, and what we do experience is the phenomenal world as conveyed by our senses, this conveyance processed by the machinery of the mind and nervous system. Kant focused upon this processing. Kant believed in a priori knowledge arrived at independent of experience, so-called synthetic a priori knowledge. In particular, he thought that by introspection some aspects of the filtering mechanisms of the mind/brain/nervous system could be discovered. These observations summarize Kant's views upon the subject-object problem, called Kant's Copernican revolution. It was the inversion of the traditional relation between the observing subject and the outer object of knowledge: "It has hitherto been assumed that our cognition must conform to the objects; but all attempts to ascertain anything about these objects a priori, by means of conceptions, and thus to extend the range of our knowledge, have been rendered abortive by this assumption. Let us then make the experiment whether we may not be more successful in metaphysics, if we assume that the objects must conform to our cognition. This appears, at all events, to accord better with the possibility of our gaining the end we have in view, that is to say, of arriving at the cognition of objects a priori, of determining something with respect to these objects, before they are given to us. We here propose to do just what Copernicus did in attempting to explain the celestial movements. When he found that he could make no progress by assuming that all the heavenly bodies revolved round the spectator, he reversed the process, and tried the experiment of assuming that the spectator revolved, while the stars remained at rest. We may make the same experiment with regard to the intuition of objects." —Immanuel Kant: English translation by J. M. D. Meiklejohn of The Critique of Pure Reason 1781 Kant's successors Fichte (1762-1814), Schelling ( 1775-1854) and Hegel (1770-1831) also raised the issue of the relationship between the subject and the object, or what perceives and what is perceived, and stressed the importance of the subject, the observer. Fichte placed the demands of the individual self or ego as the starting point of all philosophical reflection. He transformed Kant's view, that the laws of rationality are set by forms of human understanding, instead into demands of the individual will. Hegel also rejected Kant's view that there was a noumenal world causing our experiences and instead proposed that the mind-shaped phenomenal world is the world. Hegel proposed that 'truth' was approached by a dialectical method, that is, a clash of an idea and its opposite, a succession of thesis and antithesis, followed by a synthesis of the two, and on, and on, a picture he felt described the evolution of history in an ever-upward spiral to 'truth'. Although a popular figure, many other philosophers found Hegel unintelligible, with Bertrand Russell suggesting Hegel's work as a model of the imprecise use of language, and A.J. Ayer declaring that most of Hegel's sentences said nothing at all. Schopenhauer (1788-1860) claimed that “everything that exists for knowledge, and hence the whole of this world, is only object in relation to the subject, perception of the perceiver, in a word, representation.” According to him there can be "No object without subject" because "everything objective is already conditioned as such in manifold ways by the knowing subject with the forms of its knowing, and presupposes these forms; consequently it wholly disappears when the subject is thought away.". Schopenhauer also asserted that the 'principle of sufficient reason' does not apply between subject and object, but only between objects. Therefore, Fichte was mistaken when he posited that the subject produces or causes the object. Realism and Materialism also are wrong when they assert that the object causes the subject. In 20th and 21st century philosophy In his lecture "Mind and Matter," Erwin Schrödinger stressed the distancing of the knowing subject from its 'objective' formulation of the world around us: "By this I mean the thing that is so frequently called the 'hypothesis of the real world' around us. I maintain that it amounts to certain simplifications which we adopt in order to master the infinitely intricate problem of nature. Without being aware of it... we exclude the Subject of Cognizance [knowing subject] from the domain of nature that we endeavor to understand. We step with our own person back into the part of an onlooker who does not belong to the world, which by this very procedure becomes an objective world." —Erwin Schrödinger: Mind and Matter He claimed that we are unaware "of the fact that a moderately satisfying picture of the world has only been reached at the high price of taking ourselves out of the picture, stepping back into the role of a non-concerned observer." As a result, in formulating the concept of the object, the subject is not considered at all. Schrödinger continues: "So we are faced with the following remarkable situation. While the stuff from which our world picture is built is yielded exclusively from the sense organs as organs [that is, agents] of the mind, so that every man's world picture is and always remains a construct of the mind and cannot be proved to have any other existence, yet the conscious mind itself remains a stranger within that construct, it has no living space in it, you can spot it nowhere in space...To learn that it [the personality of a human being] cannot really be found there [in the interior of a human body] is so amazing that it meets with doubts and hesitation, we are very loath to admit it." —Erwin Schrödinger: Mind and Matter These observations are supplemented by those of Northoff mentioned above. The knowing subject can be brought into the discussion by considering how it colors its own observations. As stated by Schopenhauer: " ‘ The world is my representation: ’ — this is a truth which holds good for everything that lives and knows, though man alone can bring it into reflective and abstract consciousness. If he really does this, he has attained to philosophical wisdom. It then becomes clear and certain to him that he does not know a sun and an earth, but only an eye that sees a sun, a hand that feels an earth; that the world which surrounds him is there only as representation, in other words, only in reference to another thing, the consciousness, which is himself." —Arthur Schopenhauer: The World as Will and Representation, p. 3 The role of the 'knowing subject' involves its limitations. Of course, language is indispensable in the formulation and communication of our perceptions of the objective world, as was pointed out by Wittgenstein: "The main point is the theory of what can be expressed (gesagt) by propositions — i.e. by language (and, what comes to the same, what can be thought) and what cannot be expressed by propositions, but only shown (gezeigt); which, I believe, is the cardinal problem of philosophy." —Ludwig Wittgenstein; quoted by Russell Nieli Chomsky and Pinker have taken this idea further back than languages that are actually in use, to a question of how the brain itself functions: "People do not think in English or Chinese or Apache; they think in a language of thought. This language of thought probably looks a bit like all these languages;...But compared with any given language, mentalese must be richer in some ways and simpler in others." —Steven Pinker: The Language Instinct, p. 72 Thus, like Kant, Chomsky and Pinker raise the issue of the mind's inherent programming. Chomsky selected as a particular example the acquiring of language by children. Chomsky marshaled evidence that a child's rapid mastery of the complexity of language indicated an innate ability programmed into the development of the human mind from birth that could not be explained by the "blank slate" view of the infant mind. Rather, the mind has a built-in propensity to process symbolic representations. The origins of this ability were sought by Pinker in a Darwinian struggle that established the survival value of the ability to communicate. According to Pinker, Charles Darwin himself "concluded that language ability is 'an instinctive tendency to acquire an art', a design that is not peculiar to humans but seen in other species such as song-learning birds." These ideas still are under examination. Among the modern essays into the subject-object problem are the fields of cognitive psychology, behavioral genetics and evolutionary psychology. References