Psychology may be briefly defined as the science of mental phenomena. After having long occupied a doubtful place as a department of metaphysics, supplemented by many empirical observations, its character as a science dealing with a special order of facts, and many of the laws of occurrence of these facts, may now be said to be established. At the same time opinion is still far from unanimous on many of the most important points of psychological doctrine, especially on such points as involve a philosophical view of the nature of mind.
The chief different ways of conceiving and defining the mental facts with which psychology has to do may be traced to the influence of rival philosophical hypotheses as to the nature of mind. Thus, in the first place, we have the view that psychology deals with the facts of the conscious mind which, when knowing, feeling, or striving, is always conscious of itself as knowing, feeling, or striving—i.e. is self-conscious. This is the view, for instance, of Sir W. Hamilton. But it has many difficulties. We can hardly ascribe self-consciousness to the lower animals or to very young children, and yet some kind of mental life clearly belongs to them: so that it would seem that mental life and self-consciousness cannot be identified. Further, many psychologists (including Hamilton) are of opinion that there are mental phenomena unaccompanied by self-consciousness even in mature human life. And if self-consciousness is thus recognised as belonging to mental life only under certain conditions and at a comparatively developed stage, it will be one of the main purposes of psychology to examine these conditions and trace its growth. In the second place, a materialistic view of mind is connected with the attempt to make brain-physiology play the part of a psychology. It is plain, however, that a sensation or a feeling of pleasure or pain is a fact of an entirely different order from a neural disturbance. The one may accompany or even cause the other (or both may be only different aspects of the same ultimate existence), but the characteristic nature of the mental fact is not reached by the most thorough investigation of its physiological conditions, while the latter are in many cases much more obscure than the phenomena they are adduced to explain. In the third place, an attempt has been made (sometimes apart from any philosophical hypothesis as to the nature of mind) to start with certain mental facts—called presentations, sensations, or feelings—regarded as ultimate or independent, and to trace the laws and manner of their combination and succession. This method has been worked with excellent result by the English Associationist psychologists. By a similar method, and by treating presentations as forces, Herbart and his followers have elaborated a mechanism of the mind and reduced psychology to mathematical form. The difficulty of this mode of conceiving mind is to explain how a series of sensations—or any interaction of presentations—can generate the consciousness of a self persisting through changing states; and even to give any meaning to sensation or presentation without regarding it as experienced by or presented to mind. On these grounds many psychologists, while influenced by the scientific method of the Associationists and of Herbart, hold that presentation or sensation is only conceivable as belonging to a subject or mind. So far, mind must be assumed by the psychologist as implied in the experience of which he has to trace the development. This subject, or mind as the condition of experience, may be admitted to elude psychological observation. As Hume says: 'I never can catch myself at any time without a perception, and never can observe anything but the perception'—i.e. it is the empirical ego, or mind with its content of experience, which is the object of psychological observation. But the pure ego, or subject, is nevertheless implied by every mental fact. Psychology may, in this way, be distinguished from other sciences as dealing with subjective facts, or, rather, with the subjective aspect which belongs to all facts—i.e., as Dr J. Ward puts it, with the phenomena connected with presentation to a subject.
Method of Psychology.—If this view of the subject-matter of psychology be adopted, it is clear that the ultimate source of our knowledge of mental facts must be the knowledge each person has, through self-consciousness, of his own mental states. The mental attitude of attending to these states is called Introspection. The nature and value of introspection have been much disputed. But the arguments of Comte and others to show that the process is impossible, and psychology only another name for a department of physiology, prove too much: for were introspection impossible we should not even know that there are such things as mental states. It may be admitted, however, that the introspective attitude involves an effort of reflection which modifies the mental state we seek to observe. Consequently many obscure elements of mental life may elude its cognisance, and only become known through their effects upon the flow of ideas; while, on the other hand, states of intense mental concentration exclude it, and can only be observed introspectively in the weakened form of memory-images. It is even held by many writers that this is the sole method of introspective observation: that all introspection is retrospection. In this way the results of introspection are apt to lack accuracy, and (as each observer is limited to his own consciousness) they also lack objective or universal validity. To supply these wants the introspective or subjective method has been supplemented by objective observation both of the physiological antecedents and concomitants of mental facts, and of the expressions, products, and records of conscious life. The latter are to be found in the emotional expressions and actions of normal men; in the emotional expressions and actions of children, undeveloped races, the insane, and the lower animals; in language; and in social customs and institutions. To this side of psychological study, which involves the application of the comparative method to psychology, contributions of the greatest value have been made in the Zeitschrift für Volkpsychologie und Sprachwissenschaft, edited by Lazarus and Steinthal. Further, within recent years attempts have been made to apply experimental methods to psychology. Experiments on reaction-time, for instance—i.e. on the time taken to react upon stimuli—lead to the determination of the time taken up by mental operations of different kinds and different degrees of complexity. Similar experimental methods have been adopted for investigating the accuracy of reproduction, the number of things that can be attended to at a time, &c. Laboratories, such as that at Leipzig, of which Wundt is the head, exist both in Germany and in America for the prosecution of these experimental investigations. The results of many experiments have already been recorded; but it would be premature at present to estimate the value of these results for the science of psychology. Amongst the experimenters who keep the bearing of their investigations always in view, mention should be made of Münsterberg (Beiträge zur experimentellen Psychologie, 1889 and following years).
Psycho-physics.—The experimental inquiries above referred to may to a large extent be traced to certain investigations (chiefly) of E. H. Weber's on minima sensibilia and on the relation between the intensity of the sense-stimulus (which can be measured objectively) and the intensity of the consequent sensation (which cannot be directly measured). His experiments were further carried out and their results formulated and elaborated into the science of psycho-physics by G. T. Fechner (Elemente der Psychophysik, 1860; reprinted 1889). By psycho-physics Fechner means the exact science of the relations between body and mind, this science being based upon facts and the mathematical relations they involve. The generalisation arrived at from experiment is by Fechner called Weber's Law, and expressed by him in the following (amongst other) terms: There will be the same sensible difference of intensity between two sensations, provided the relative intensities of the stimuli producing them remains the same. Thus, an increase of 1 to a stimulus whose strength is expressed by 100 will be experienced as of the same intensity as an increase of 2 to a stimulus whose strength is 200, or of 3 to a stimulus whose strength is 300, &c. The literature of psycho-physics is occupied with the experimental verification, the mathematical development, and the interpretation of this law. But neither its experimental basis nor its interpretation is quite satisfactory. Experiment supports it only within a certain range of sensibility. It is limited first of all by what Fechner calls the 'fact of the threshold'—i.e. the fact that a certain amount of stimulus is required to produce any sensible effect whatever; and secondly, at the other end of the scale, when the stimulus is beyond a certain intensity, the relation ceases to hold good, while within these two limits its verification cannot be said to be exact. Further, it is only in the sense of pressure and the muscular sense that we can accurately measure the intensity of the stimulus in the form in which it reaches the nervous end-organs; in hearing and sight the objective stimuli undergo physical or chemical changes in the sense-organ before reaching the extremities of the nerve- fibres. Again, all the experimental methods for establishing the law assume the equality of least sensible differences. Thus, if there be stimuli measured respectively by 100, 101, 200, 202, causing sensations , such that is only just distinguishable from , only just distinguishable from , it is assumed that , an assumption which neglects the important fact that there is no mental content corresponding either to or to . Finally, even if the law can be held to be established, it is not clear that it requires to be interpreted (with Fechner) as properly psycho-physical. It may also be held that the law is really physiological, the intensity of the stimulus being modified in this way by irradiation in the nerve-centres; while Wundt has attempted a psychological interpretation of it, maintaining that it holds of the relation between mere sensation and the 'apperection' of the sensation by the direction of attention to it.
Mental 'Faculties.'—The observation and description of mental facts have led to a classification of them, according to their degrees of likeness, into certain orders; and these have been frequently spoken of as different powers or functions of the mind. In the earliest stage of psychological inquiry we even have them described as different parts of the soul. In this way Plato distinguishes desire, anger, and reason, and locates them in the lower part of the body, in the heart, and in the brain respectively. But the classification which had most influence upon subsequent writers was Aristotle's. His distinction of thought and desire is the origin of the dual classification of intellectual and active powers (each with many subdivisions) which was for long almost unanimously adopted. A tripartite classification—Cognition, Feeling, and Desire or Will—was put forward by the psychologists of Kant's time, accepted by Kant, and since his time (in Great Britain since Hamilton's time) has been very generally adopted. The value of such classifications is easily, and has often been, overestimated. In the first place, it is clear that, although such functions or faculties may be distinguished, they do not operate apart from one another. No concrete state of mind consists merely of knowledge or merely of will; nor can it be properly called by one of these names, except as a means of describing it by its most prominent characteristic. In the second place, it has to be borne in mind that it is no explanation of a mental fact to refer it to a mental faculty. To maintain, as Kant, Hamilton, and Lotze did, that there are certain fundamental conscious functions or conscious elements which cannot be reduced to some single function or element, gives no real support to the view which seems to underlie much of the 'faculty-psychology'—the view that mind is a congeries of distinct faculties, and psychology a process of labelling facts and putting each into its proper compartment. To refer phenomena to memory, generalisation, &c. as their causes is to mistake a name for an explanation.
The 'Faculty-psychology' described and demolished by the English Associationists and by Herbert is, however, rather a mode of thought into which certain writers have frequently lapsed than a method which they have consciously adopted and defended. And the quest for a simple and uniform mental element from which all the wealth of conscious life has been derived is not therefore successful, because the faculty-psychology is unsuccessful. Herbert regards the interaction of presentations as accounting for all mental phenomena; in a similar way H. Spencer seeks to derive mind from a succession of somethings which can only be described as analogous to nervous shocks. But the difficulty of both is to pass from this objective element to the feeling of pleasure or pain, aptly described by Hamilton as subjectively subjective, or to the phenomena of Volition. Accordingly, many psychologists who are at one with Herbert and the Associationists in rejecting the conception of faculties as a mode of explaining facts yet hold that the final analysis we can reach of consciousness or of mental phenomena does not enable us to derive subjective feeling (of pleasure or pain) from presentation, or activity from either, the three elements being involved in the simplest state of consciousness (the term 'consciousness,' as distinguished from 'self-consciousness,' being here used as a quite general term for any mental state).
Attention.—Many of the most important controversies of psychology centre in the question of the nature and extent of the activity involved in consciousness. In its simplest form this activity is seen in the subjective reaction involved in apprehending a presentation; in its most developed form it is the act of will which determines a course of conduct upon which momentous issues are known to hang. In the latter case, as well as in the former, the critical point is the direction of Attention. Now attention is generally allowed not to be a special 'faculty,' or separate activity different from the elements of consciousness already described. It is simply consciousness regarded as active and as concentrated on some portion of its objective content, whereby the intensity of that portion is increased. The point in dispute is chiefly whether this active concentration is ultimately determined by the strength of external factors. It is clear that the direction of attention is conditioned by the previous mental groupings of ideas. Further, attention involves a muscular adjustment—at any rate when directed to objects of sense, and also (although in a less marked degree) when directed to a train of thought. These facts are differently interpreted. On the one hand, Bain, Ribot, and others find the basis of attention in the muscular adjustment; on the other hand, the muscular adjustment is looked upon as the organic expression and development of subjective activity; and this subjective activity is held to be involved in the simplest state of consciousness. The one view looks upon the external as determining and even somehow producing the internal. According to the other view the process is one in which a subjective or spiritual factor expresses itself through and gradually extends its control over an organic and physical environment.
Sensation.—Sensations are commonly defined as the simple mental states which result from nervous stimuli. This physiological reference enables us to distinguish the Special Senses, with their clearly defined organs adapted to the reception of different kinds of external stimuli, from Organic or General Sensibility, which arises from the state of the internal organs of the body (such as the alimentary canal, the lungs, and the heart), and from the Motor Sensations. These last (which play so important a part in the development of knowledge) are due to the central excitation of a motor or efferent nerve, and the consequent contraction of the muscle in which it terminates (see MUSCLE, NERVOUS SYSTEM). The sensation both modifies and is modified by the conscious state into which it enters. We have no experience, and can form no valid conception, of the mere sensation. For the subject which experiences it, it is merely an element in a complex and ever-changing whole. This is a point which has been commonly overlooked by the Associationist psychologists. They started with a succession of disconnected mental molecules, called sensations, and attempted to trace the growth of mental life from their combination. But this is to begin with an abstraction.
The earliest stage of mental life would rather seem to be a vague manifold into which distinction is just being brought; and the growth of knowledge consists not only in the addition of new elements, but in drawing new lines of distinction and forming new groupings of elements. And these distinctions and groupings may be said to be determined by the varying intensities of different elements in the changing mental content, or by the continuous redistribution of attention.
Ideation.—The mental content thus varies in the distinctness of its parts, which may even disappear from consciousness and afterwards reappear. This reinstatement in consciousness is called Representation or Ideation, and the represented or ideal contents are called Images. The circumstances determining the succession of ideas and formation of images are, first, new sense-impressions; secondly, voluntary direction of attention; and thirdly, the mutual influence of the mental elements. It is the last of these which is referred to under the title of Laws of Association. In the article ASSOCIATION OF IDEAS an account is given of the way in which one concrete experience recalls another. In every case of association a twofold process would seem to be involved. A portion of the present mental content coalesces with a resembling portion of a past mental state, and the revival of this portion involves the reinstatement in consciousness of the other elements with which it was previously connected. The latter, which is the properly reproductive process, is thus due to the fact that consciousness is not a collection of atomic sensations, but a continuous whole.
Perception is the knowledge by means of sensation of an individual object or thing. The nucleus of the percept is thus one or more present sensations which coalesce with revived or ideal elements belonging to the same sense, and combine with revived or ideal elements belonging to other senses. These presentative and representative elements are bound together and presented as a single mental content, which we refer to a portion of the body or to a thing in space beyond the body, and to which we ascribe qualities corresponding to our sensations. In brief, Perception, as distinguished from Sensation, involves, first, complexity of elements; secondly, localisation; and thirdly, individualisation and objectification. The complexity consists of the elements of present sensation, and of the ideal group with which the former coalesce or combine. The localisation clearly involves the perception of space. The individualisation and objectification may be accounted for by the following considerations: (a) The various sensations grouped together in a percept—e.g. the resistance, touch, colour, taste, smell of an orange—are so related that modification of one of them commonly involves modification of the others. Thus they come to be perceived as a group. (b) Not only are motor sensations involved in fixing attention on other sensations, but the greatest distinctness of the other sensations is commonly accompanied by conditions which admit also of sensations of touch and resistance. Hence the object comes to be experienced as offering resistance or as an obstacle. (c) In this way the other sensations come to suggest touch and resistance, and thus to be referred to a thing in space which offers resistance to our muscular energy. This forms the psychological basis of the distinction between primary and secondary qualities of matter.
The above account traces the perception of objects in so far as it is mainly dependent upon active touch—i.e. touch plus its attendant motor sensations. To active sight—i.e. sight plus its attendant motor sensations—a perception is due which differs from the preceding (a) in the absence of the sensation of resistance: so that we do not derive from active sight alone a knowledge of objects outside of and opposed to our own bodies, and our apparently direct perception of distance, solidity, &c. by sight is really a derived perception; (b) in the vastly greater number of elements simultaneously presented, so that the simultaneity of perception which characterises the developed perception of space is mainly due to visual perception.
Space and Time.—As the preceding paragraph points out, objects or things are perceived as in space. Similarly, our conscious life is apprehended as a succession—i.e. as in time. The whole of our experience may thus be said to be conditioned by Space and Time: the phenomena of external perception by space, those of internal perception by time. The two spheres are sometimes described as the object-world and the subject-world respectively. Regarding both space and time there are several questions which admit of being kept distinct. First of all, there is the question as to their reality—are they real existences, or simply modes of our subjective perception? This is a question which properly lies outside psychology, and belongs to metaphysics. Then there is the question of the way in which we form concepts of space and time. Geometry depends upon such a conception of space. The points, lines, and surfaces of geometry are not percepts, but abstractions from perception, formed as other concepts are formed. What then is that in perception from which we are able to form concepts of space and time? It must itself be a spatial or temporal percept. It is then with regard to the perceptions of space and time that the most difficult psychological question enters. And the question regarding both perceptions is affected by the secular controversy concerning the existence and the function of an a priori factor in mind.
Thus we start with two opposed views of the perception of space: first, the Intuitive or Nativist theory, according to which space is an innate idea (or, as since Kant it has more commonly been put, is the form in which we perceive objects), and is not derived from sensations, but is a form of perceiving, belonging a priori to the mind, and contributed by it in the production of experience; secondly, the Empirical theory, according to which space is the worked-up product of sensations. The universal and necessary character of the spatial perception has been brought forward in defence of the former theory. But it is important to remember that certain sensations—odours, tastes, and even sounds—are localised only indirectly, as belonging to a visible or tangible object. And this fact at once suggests the lines upon which an empirical analysis of space should be carried out. By Herbart space has been derived from a series of sensations which can be repeated in the same and in reverse order. By Bain it has been held that it is due to muscular sensation—movement giving the perception of empty space, resistance giving that of space filled or body. Sensations both of movement and resistance accompany touch; and sensations of movement accompany sight to an extent which is not nearly equalled in the other senses. In addition to this, however, we must take account of what Lotze calls the 'local signs' which belong to tactile and visual sensations. These local signs are due to the extended nature of the sense-organs of sight and touch, and are elements in sensation by which sensations arising from the stimulation of different portions of the retina (or of the skin) are distinguished from one another. The simultaneous distinctness in sensation which is due to these 'local signs' is gradually interpreted by motor sensations, and out of these elements there gradually emerges the perception of one's own body, by relation to which other things are localised in space. Thns, although the perception of space is implied in that of body, the two perceptions grow to clearness together. Even admitting this empirical analysis, however, it may still be held—as Lotze holds—that there is an a priori mental tendency to form the perception of space.
The opposed views of Nativism and Empiricism are applied to the perception of time as well as to that of space. And the perception of time only seems a simpler question than the other because we are apt to confuse the succession of presentations on which it is based with a presentation of succession, which, of course, would be a presentation of time. The elements from which this presentation of time is derived may be somewhat as follows: When a number of presentations are successively presented, each grows fainter as attention passes from it, and hence arises a vague distinction between present and not-present. Afterwards, on the same series being repeated, the second member will be rising in intensity when the first is presented, and therefore in full intensity; when the second is presented, the first will be sinking in intensity, while attention will be passing on towards the third, whose intensity will therefore be rising; and so on throughout the series. Hence the vague distinction of present and not-present becomes more definite as a distinction of past, present, and future, and this is the presentation of time.
Memory and Expectation.—Both of these are distinguished from the mere succession of ideas and images by involving a reference to one's own conscious life as a succession in time. When an image is remembered its various parts have a fixed order and position, it is accompanied by a number of attendant or accessory ideas, and it is recognised as belonging to one's past self. The expected image has not always the same fixed position or number of attendant ideas; but it, too, is referred to self—one's future self, and it is characterised by an element of striving or tension and by an increasing degree of intensity. The phenomena of memory and expectation are a recognised difficulty for the theory which seeks to derive mind from the succession of presentations.
Thought.—In the process of thinking different mental contents are related together—generalised into notions or concepts, discriminated, and in the higher forms of thought, arranged in an orderly manner under some scientific or other ideal. Thinking is further distinguished from perception and imagination by dealing with classes of things rather than particular objects, and by being mainly voluntary, whereas perception is mainly automatic. But the distinction is not an absolute one. In imagination and even in perception a process of voluntary selection may be involved, and every clear perception involves a conception of a class to which the object is referred. Further, the relating process which is characteristic of thinking may be found, though in a less explicit manner, involved in perception: for the percept has been shown to consist of a variety of elements connected together in definite ways. Carrying the analysis further, we can find no conscious content without such relations. This has been commonly brought out by emphasising the necessity of difference for consciousness. Thus, Hobbes made the assertion that 'to have always the same sensation and to have no sensation at all come to the same thing'; and this has been formulated by Bain into the Law of Relativity, that all consciousness is consciousness of difference: not, indeed (as Bain some- times puts it), that we are conscious only of difference, but that all consciousness involves difference or discrimination; as it may also be shown to involve likeness or assimilation and synthesis.
Relations are thus involved in all consciousness equally with elements related. 'Feelings' and 'relations between feelings' (to use Mr Spencer's terminology) must be regarded as equally ultimate in mind. The English Associationists made consciousness begin with separate units of sensation or 'feeling'; and those writers who have received and carry on the tradition of the Associationists have devoted much attention to determining the nature of these relations. But if the ultimate datum of consciousness is not separate atoms of presentation, but what Dr Ward calls a presentation-continuum, and if the growth of mind consists not merely in additions to that continuum, but in drawing new lines of distinction and connection within it, we may see how neither the so-called 'feeling' nor the so-called 'relation between feelings' is independent and conceivable by itself, and how both are simply abstractions from the state of mind which—even at its simplest—is a concrete phenomenon. In other words, what is characteristic of thought as well as what is characteristic of sensation is involved in all consciousness.
Feeling and the Emotions.—The term Feeling is of very ambiguous signification in psychology. But there is a pretty general agreement to use it for the second of the three elements in the tripartite division of mind (although, unfortunately, it has not been restricted to that use). The psychology of feeling has two chief problems to deal with: first, to determine the nature and conditions of pleasure and pain, as contrasted with other elements of mental life; and secondly, to analyse into their elements, and trace the growth of, the complex feelings or emotions. The Emotions are complex states of mind in which a feeling of pleasure or pain is predominant. This feeling is connected, more or less distinctly, with a presented or ideal object, and is complicated with elements of organic sensation, and, usually, with tendencies to action or elements of desire. These complex states of feeling, or emotions, take very various forms, according to the elements of which they are composed, and their mode of origin. The classification of the emotions and the nature and origin of such emotions as sympathy and the moral sentiment are still vexed questions of psychology.
Desire and Volition.—In these phenomena we have the development of the active element in mind complicated with feeling and manifesting itself in muscular activity. Writers who regard this active element as ultimately due to the play of merely presented or external factors have attempted to derive volition from spontaneous movement (Bain) or from reflex action (H. Spencer)—factors which enter consciousness merely as motor presentations. As opposed to this we have the view that the fundamental act of will is the direction of attention to certain ideal elements or groups. Whether this direction of attention is itself determined solely by pleasure and pain is a question which has raised more controversy than perhaps any other question in psychology (see WILL). In Desire there is present the conception of an object or ideal end, accompanied by feeling and by an element of striving. Normally, when the conception of the end has been associated with definite means to its realisation, the desire is followed by a volition or act of will. The development of volition is a process of growing complexity and definiteness. Beginning with the act of attention, the power of will is gradually extended over the bodily movements controlled by muscles in connection with the motor nerves. Movements which are at first random, reflex, instinctive, or merely expressive, are brought within its operation. Further, will grows side by side with reason and imagination, is called into operation not by sense-presentation only, but in response to images and concepts, and can thus be regulated by reason. A double tendency is at work in this development: the associative and automatic tendency of acts frequently repeated to become habitual; and the intellectual tendency by which ends and the acts tending towards them are brought into rational order. In this way the individual comes to act for permanent ends and from fixed principles, and to develop a definite character.
LITERATURE.—The first scientific treatise on psychology was Aristotle's work De Anima. In modern philosophy an intentional and spiritualist theory of psychology is to be found in Descartes and Leibnitz, an empirical and materialistic theory in Hobbes. The Association-psychology, which traces descent from the psychological philosophies of Locke and Hume, and from the physiological psychology of Hartley (Observations on Man, 1749), may be read now in the works of James Mill (Analysis of the Phenomena of the Human Mind, J. S. Mill's ed. 1869), J. S. Mill (Examination of Hamilton's Philosophy, 5th ed. 1878), and A. Bain (The Senses and the Intellect, 3d ed. 1868; The Emotions and the Will, 3d ed. 1880; Mental and Moral Science, 3d ed. 1875). Belonging to the same school, but conditioned throughout by the doctrine of evolution, is H. Spencer's Principles of Psychology (2d ed. 1870-72). To the Herbartian influence is due the exhaustive text-book of W. Volkman von Volkmar (Lehrbuch der Psychologie, 3d ed. 1884). Independent views, which are yet influenced by Herbart, are worked out by Lotze (Medicinische Psychologie, 1852; book iii. of Metaphysics, Eng. trans. 1884; Microcosmus, Eng. trans. 1885; Outlines of Psychology, Eng. trans. 1886) and by J. Ward (article 'Psychology' in Ency. Brit., 9th ed.). Experimental psychology is represented by the works, among others, of Wundt, Ebbinghaus, Münsterberg, Ribot, Pierre Janet, and by many contributions to German, French, Italian, English, and American journals. A useful summary of results is given by G. T. Ladd, Elements of Physiological Psychology (1887). Founded largely upon these is the brilliant work of W. James, Principles of Psychology (1890). Important text-books are Sully's Outlines of Psychology (1884) and The Human Mind (1892), Baldwin's Handbook of Psychology: Senses and Intellect (2d ed. 1890) and his Elements (1893), Dewey's Psychology (1889), J. C. Murray's Handbook of Psychology (1885), Höffding's Outlines of Psychology (Eng. trans. 1891), and Maher's Psychology (R. Catholic, 1890). Wundt's Lectures on Animal and Human Psychology were translated in 1894: C. Lloyd Morgan has published An Introduction to Comparative Psychology (1894) and Psychology for Teachers (1893); and G. T. Ladd a Primer of Psychology (1894). See also PHILOSOPHY, and other articles cited there.