The Neural Processing of Complex Sounds, by T.D. Griffiths

Griffiths presents research investigating the temporal neural processing of complex sounds. Complex sounds is defined through a modular representation of sound perception relevant to music. Simple processing includes “neural encoding of simple temporal, spectral, and spatial information,” complex processing includes “stabilized representation of temporal spectral, and spatial patterns,” while semantic processing involves “symbolic use of auditory ‘tokens’ derives from complex sound processing.” This model seems quite useful, as it seems that much research reporting on the neural response to music is really reporting on what is defined here as simple processing. Griffiths here takes a larger view and looks at a higher level of musical material and the ways that these might effect the brain in ways not present in the other two ways presented of processing sound.

Functional imaging studies such as PET, fMRI, and MEG; and psychophysiological studies of patients with brain lesions allow the author to take two avenues for pursuing this research. The author states that functional imaging studies allow the researcher to see the processes normally involved in temporal analysis, while lesion studies show the researcher the necessary processes involved in temporal analysis. Beyond this, he also divides these processes into fine and higher-order temporal analysis. Fine temporal analysis is at the level of milliseconds or tens of milliseconds, while higher-order temporal analysis is at the level of patters of pitch, duration, etc.

Both functional imaging and lesion studies show “evidence for the existence of a neural substrate for the processing of sound sequences that is hierarchical in organization” (p. 175). The auditory cortices, and the pathways leading to them, are likely to provide a sufficient (necessary) mechanism for the processing of “simple sounds,” as defined above. However, for the processing of “complex sounds,” as defined above (and the higher hierarchical division of “semantic processing” as defined above), bilateral temperofrontral networks are likely required.

These findings show the importance of considering exactly what is defined as “musical perception” in various studies, as there are apparently different mechanisms involved in the psychophysiology of the temporal processing of complex music.

WEEK 5: Musical Preference and Taste: 3.3, The Listener

North and Hargreaves consider multiple variables on musical preference and taste in this chapter, including ethnicity, social class, socioeconomic status, “taste publics,” massification, religion, age, sex, and personality. They also discuss the same topics in non-humans. Rather than giving clear opinions, they authors present a vast body of research on these areas, with rather little commentary upon methodology etc. of the research they cite. They often present conflicting points of view, and it can be difficult to know which studies were more convincing based on the presentation. Nonetheless, the reader acquires a clear overview of research into the topic and is left to make their own educated decisions and opinions.

Concerning the effect of ethnicity on musical preference and taste, the authors basically conclude that there is little research that has examined this area. However, they do cite one 1993 study where Black people had a statically stronger preference for music by people whom they identified as Black, while White people had no significant difference between their preference in music between Black and White performers. Research in this area is tentative at best.

While discussing social class, the summary of the research presented is that those of higher socio-economic class prefer art (or “classical”) music, while those with lower ones prefer pop music. They note, wisely, that much of the research is tentative and doesn’t control for other possible variables effecting the research. The role of the recording industry in preventing diversity of music is discussed directly: why would the recording industry take chances with a diverse range of music when they can make more money by simply doing the same thing that is already bringing them money. The authors argue that this may lead to a “massification” where musical tastes in our culture have become more homogeneous.

Research on “taste cultures,” that is, groups of people who “express values and standards of taste and aesthetics,” (p. 103) is reviewed. The cited research identified five main American taste cultures: high-culture, upper-middle culture, lower-middle culture, low culture, and quasi-folk-low culture. They cite research that shows that the largest variables that effect musical preference were religious preference and social class. The authors point out the lack of consideration that such studies have show for varying uses of music by different social groups, which could have profound findings.

Regarding the topic of age, a model by LeBlanc is offered (1991): “(a) younger children are more open-eared, (b) open-earedness declines as the child enters adolescence, (c) there is a partial rebound of open-earedness as the listen matures from adolescence to young adulthood, and (d) open earedness declines as the listener matures to old age.” Various other studies conflicts or affirming this model is presented. The importance of late adolescence and young adulthood (to about age 24) is considered an important age for developing musical tastes, according to much of the research presented. The authors present the possibility and implications of musical development in the womb.

Regarding sex and musical taste and preference, the authors state that research indicates that girls generally like music more, though this is changing as technology is used in music more – a domain where boys apparently feel more comfortable. One interested study by North, Hargreaves and O’Neill (1998) showed that boys were more likely to listen to music for impression management on others, while girls were more likely to listen to music to meet emotional needs.

Regarding personality, the authors discuss the possibility of using music as a compensation mechanism (introverts use music to calm down, etc.), and also the possibility of music as a way to reflect personality (introverts use music to reflect their inner moods, etc.). Listening strategies are discussed, and listeners are basically divided into “objective-analytic”/”cognitive” listeners, or “affective”/”associative” listeners – definitely an exercise in reductionism.

Regarding music responses in non-humans, various studies are cited where animal welfare has been altered using music and the musical response of different animals. The results are interesting but tentative.

I found this to be a good overview of the existing research in this area, though I would have liked to have know more about the methodologies involved in the various research cited so that I could make informed decisions about which studies are more rigorous.

http://www.arthurs-clipart.org/medical/senseorgans/cochlea%20diagram.gif

Lipscomb and Hodges provide a concise yet thorough overview of hearing and perception of sound and music. The chapter is organized by essentially tracing a soundwave from outside of the body, to inside the ear, to the brain and then to psychological attributes of sound.

The outer ear (pinna), middle ear (between the ear drum and cochlea; air-filled), and inner ear (semicircular canals and cochlea) are described. In particular, the cochlea is discussed fairly thoroughly; the vestibular canal, tympanic canal, helicotrema, round window, tectorial membrane, basiliar membrane (responsible in part for pitch recognition), outer and inner hair cells are described and their respective functions delineated.

The hair cells in the cochlea transfer mechanical energy of the waves in the cochlear fluid to electrochemical energy which then travels to the brain via the auditory nerve. Within the brain, multiple cites are responsible for the processing of the information received from the auditory nerve, and these are discussed.

The authors then proceed to correlate physical and perceptual (psychological) variables of sound according to the theories set forth by Carl Seashore. Seashore adds a third variable to the physical and perceptual levels: what he called “trunklines of musicality.” The correspondences are as follows (physical/perceptual/trunkline): frequency/pitch/tonal, amplitude/loudness/dynamic, signal shape/timbre/qualitative, and time/duration/temporal. Each of these points is the discussed, after an explanation of the critical band.

Consonance, dissonance, simultaneous tones, hearing loss, masking, overtones/harmonics, and psychological constructs of the “present” in terms of time are all explained in this chapter as well, though the required brevity of this summary does not permit a further exploration of these here.

Finally, the authors discuss anomalies in Seashore’s model, noting research indicating that the relationship between the acoustical and psychoacoustical phenomena delineated by Seashore are not entirely accurate (though they still provide a good functional model).

Personally, if I had to choose one chapter to summarize hearing and perception, this would be it. The writing is clear and the required content is covered without too much superfluous material or too elementary of a treatment.

Brain Mechanisms - Altenmuller & Gruhn

It is essential, to all learning, that one acquire the necessary vocabulary to thoroughly understand the concepts being taught. Altenmuller and Gruhn provide exactly that in their definitions of various brain mechanisms. A brief summary includes:
1) Brain imaging methods – the monitoring and documenting of neuronal activity during music perception, reasoning, and production. EEG (eletronencephalography) measures electrical activity of the neurons in the cerebral cortex and MEG (magnetoencephalography) assesses brain metabolism, cerebral flow, and O2 consumption of nerve cells.
2) Structure of the brain – hindbrain (medulla, pons, cerebellum) together with the midbrain constitute the brainstem, which regulates all vital and many sensory and motor functions. The midbrain (thalamus, hypothalamus). The forebrain (basal ganglia, hippocampus, amygdaloid nucleaus). The cerebral cortex (outer part of brain) constitutes both hemispheres of the brain each consisting of frontal (movement and future planning), temporal, parietal (somatic sensation, body imaging), and occipital lobes (vision processing).

The perception of music through the complex workings of the above terms begins with pitch and dynamic recognition, extends to timbre, and then auditory gestalt (form). These acoustic, patterns, associations, emotions, and expectations distinctions are based on new learning patterns as well as previously experienced patterns.

Claims that music is essential in the brain development of young children are confirmed when comparing the motor cortex and corpus callosum of musicians and nonmusicians. Several studies have confirmed these findings along with musician’s ability to learn specific tasks through neural, auditory, and sensory-motor plasticity.

Learning in young children constitutes anatomical adaptations whereas older people require modification of brain organization (plasticity/flexibility). It is important however to mention that various approaches to teaching can greatly affect both areas of learning. Science is steadily working on creating models to better define required teaching approaches.

WEEK 4:Learning and Perceiving Musical Structures: Further Insights from Artificial Neural Networks, by Tillmann, Bharucha, and Bigand

In prior reading for this course, much of the focus has been on the capacity the human body for hearing and for ‘universals’ – or processes that are present in our biopsychological composition – in the perception of music. This chapter presents a significant departure from such a stance. Indeed, this article focuses on computer-simulated neural networks that ‘learn’ musical structure passively through mere exposure to Western music. This would represent the extreme of “nurture” in the seeming “nature versus nurture” dialogue that we have been exploring regarding the influence of human psychological composition versus acculturation in the processing of music by humans.

In this chapter, the authors present a summary of findings from the use of artificial neural networks on computers on the learning and perception of musical structures. Introductory material is given as to how such artificial neural networks function. The network consists of units (simulating a population of neurons) which ‘learn’ through repeated exposure. The patterns of learning in such a system, state the authors, can demonstrate how mere exposure (or acculturation) can function to influence musical perception.

The recent work of the authors involved what is called a Self-Organizing Map (SOM), in which units map themselves according to what is learned. The authors set up the neural network so that three levels (or “orders”) of musical syntax are recognized: tones (reduced to twelve through octave reduction), chords (three simultaneous tones) and keys (based on tone and chord recognition). By inputting tones and chords into the network, the SOM then creates the connections between the data to simulate passive learning of musical patterns (all of them from Western music in the research presented). One premise of such a system is that musical structures that are similar will emerge in close proximity in the SOM, while musical structures that are less similar will emerge in more distant proximity. This is what the researchers found; for example, key relationships emerged in a spatial pattern similar to the circle of fifths in music theory, where the keys with the most related tones are found next to each other in the circle. The authors note that the current data only relate to pitch and recognize the necessity for using a network where both pitch and rhythm are used in neural networking in future research; methods to do such are briefly discussed

The researchers summarize their findings: “Overall, the simulations showed that activation in the trained self-organizing network mirrored data of human participants in tonal perception experiments. This outcome suggests that the level of activation in tone, chord, and key units is a single unifying concept for human performance in different tasks” (p. 116).

Though the findings in the presented research are not surprising or beyond what would be expected, the promise of future developments in the area of artificial neural networks is promising, and this chapter demonstrates this potential. Though the current abilities of such networks seem limited, they nonetheless are not meaningless. As technology and neuropsychological science progresses, we can reasonably expect networks with greater power that could in turn be used for research with greater implications.

Prenatal Development - Parncutt

This chapter struck a sensitive nerve with me. I have read countless books for expectant mothers but found Parncutt’s information regarding the various biochemicals that pass from mother to unborn child, often due to stress and tension, invaluable. Nowhere in any of the ‘What to expect when you’re expecting’- Heidi Murkoff or the ‘The Girlfriend Guide to Pregnancy’-Vicki Iovine does it inform an expectant mother of these life altering facts.

Parncutt, similarly to Trehub, provides an indepth view of the sound environment of an unborn child that includes, the mother’s voice, heartbeat, breathing, digestion, outside voices, and external environment including music. High frequencies are muffled while some lower frequencies are inaudible. The most obvious organs to develop in a fetus that essentially aid in musicality are the brain and hearing/balance organs. Experiments to determine fetal hearing include heart rate acceleration/decelerations in response to sound from 20 weeks. Similarly, fetal communication between mother and fetus are tracked by behavioral states through representative biochemicals. Examples of these are endorphines associated with pain, stress, hunger, digestion and high cortisol levels, associated with anger. These all move from the mother through the umbilical chord and placenta to the fetal brain. The effects of a stressed or anxious mother often leads to premature or underweight new borns.

Parncutt address an interesting question of the purpose of prenatal hearing. This ability is limited to a small amount of mammals and has been hypothesized as a preparation for perception, language, and bonding. Research in the field has produced many inconclusive and unreliable results. The divide in prenatal psychology includes scientific-conservative literature and romantic-progressive research and much research is still being suggested for the existence of talent, music perception, and consciousness in a fetus. The issue as to whether music education should be present before birth is equally divided. There is no research that firmly establishes benefits to prenatal development and several aspects of the concept can have negative repercussions e.g. hearing damage and stress on the fetus.

Parncutt’s writing are constantly substantiated and referenced by previous research. Again, I am reminded of Pinker’s statement that ‘as far as biological cause and effect are concerned, music is useless’ and have to wonder whether Pinker ever read Parncutt.

Music, Science, and Culture

Ian Cross eloquently reveals the contrasting approaches between science and musicology, on music. Scientific research, an active and productive contributor to the research field of music has brought with it, neuroscience. A leader in the field is cognitive psychologist, Carol Krumhansl (Cognitive Foundations of Musical Pitch, 1990). Many of her experiments have provided researchers with information regarding the pitch organization of individuals, distinguishing regularities in pitch based on previous experience. Similarly, Dennis Drayna has conducted experiments in the genetic implications of musical disposition (Science, 2001). His findings claim that ‘musical ability is largely genetic’, the result of which could have a multitude of negative connotation for music education.

On the musicological side, various research has been conducted contrasting vastly from the reductionist standpoint of science. Musicologists have incorporated culture and considered both culture and history in their research.
‘…the sciences must as some point address music as grounded not only in biology but also in culture. And musicology, in particular ethnomusicology, has seen an increasing need to deal with music not only as a cultural but also as a biologically grounded phenomenon’ (153)
Cross sets out to establish a broad definition for music that takes into account both fields of research on music. He confirms several point:
1) Music is present in every culture
2) Music and movement are closely associated
3) The recognition of pulse in music
4) Ambiguity of music (contrasting greatly with language)
He developed this hypothesized definition of music, ‘music embodies, entrains, and transposably intentionalizes time in sound and action’ (155).

Children’s predisposition to engage in music-activities from birth has been hypothesized as playing an integral part in the ambiguous application of music that unlike language, is quite unique. It also enhances exploratory behavior and social development.

I thoroughly enjoyed Cross’s perspective of music in evolution. His views that perhaps the extended childhood of homo sapiens as opposed to homo habilis, heidelbergensis, and ergasterhas, contributed to man’s need to maintain child-like behavior/ambiguous music through adulthood both as a need for mediation and accommodation.

Basic Physical and Psychoacoustical Processes, Lathom-Radocy and Radocy

Lathom-Radocy and Radocy here provide an excellent, clear and accessible overview of physical and psychoacoustical processes, with an emphasis on the topics of greatest importance to musicians and music researchers. Beginning with the subheading “vibration,” the authors clearly define and discuss relationships between frequency, Hertz, amplitude, and overtones, amongst others.

The follow this by discussing the travel of sound waves, which by nature requires a physical medium. An analogy of a line of dominos toppling over, one after the next, more clearly explains the travel of a sound wave – the wave consists of physical energy transmitted from one particle in the air to the next – rather than a ball flying through the air analogy, where the actual ‘substance’ of the subject moves through space. Explaining the difference between transverse waves and longitudinal ones, they clarify why music is primarily (though not exclusively) concerned with longitudinal waves. The important properties of traveling waves are explored: speed, frequency and wavelength. Interference, reflection, refraction and diffraction. Standing waves are given a slight explanation (these are considered quite important in the Italian-Swedish school of vocal pedagogy, incidently).

After discussing sound and the waves in which it travels, the authors turn their attention to the auditory environment, discussing such topics as reverberation time (citing that generally 1 to 1.7 seconds is considered satisfactory) and sound distribution. They claim that “even [sound] distribution is encouraged by rough, irregular surfaces and a lack of an overly symmetrical shape” (p. 75), which is interesting and also stands in contrast to the design of many concert halls – especially older ones.

Next, the authors turn their attention to psychoacoustical phenomena. This primarily deals with how humans respond to physical stimuli. After cautioning that presenting a “dualistic” viewpoint is not always seen as completely accurate (and giving examples of why later), the authors proceed to describe various psychoacoustical aspects and their roughly-corresponding physical aspects. They relate frequency to pitch, intensity to loudness, and waveform to timbre. A fair amount of detail on each of these psychoacoustical phenomena is presented in a precise, if concise, manner.

Personally, I learned quite a bit from reading this. My thinking was not yet so clear and to distinguish precisely between physical- and psyco-acoustical phenomena. This article is an excellent step in clarifying that, and also an excellent step toward understanding music perception and hearing more accurately.

WEEK 3:Musical Predispositions in Infancy, Sandra E. Trehub

Trehub beings by arguing against Pinker’s idea that music in much less important from an evolutationary point-of-view than language. (Toward the end of the chapter she goes into greater detail regarding the biological significance of the findings presented in this paper, making good arguments for the evolutationary development of biological musical abilities). She then describes research with infants, mostly using a conditioning procedure where the child hears something on a speaker, repeatedly, and then looks (or fails to do so) at the speaker when something changes in the music. She cites research using this technique and others that infants recognize tranposed melodies, retain the ability to recognize a melody when the tempo is altered upon repetition, and are especially sensitive to recognition of melodic contour. Apparently contour is a feature of music where little difference is made by musical training (unlike interval processing), and Trehub makes the case that contour of melody may be especially important due to importance of such recognition while a mother is singing or speaking (in the typical style in which a mother speaks to a young child – generally higher pitch and also greater pitch variation).

She makes a good case that “…infants, children and adults detect interval changes more easily in the contxt of smaller-interger rations – the octave (2:1), perfect fifth (3:2), and perfecct fourth (4:3) – than in the context of large-integer ratios such as the tritone (45:32)” (p. 6). This suggests the importance of these intervals in Western music (and music of other cultures) may have a biological basis.

Trehub discusses scale structures, noting that “… scales with unequal steps… enhanced infant performance…” (p. 7) and that adults also have an easier time recognizing poorly tuned tones in scales that have unequal steps – a potential explanation of why the music of most cultures employs such scaler structure.

Trehub then discusses maternal music. Emphasizing the importance of a mother’s singing to her child, she explains the many effects of such singing on both infant and mother – in terms of bonding, arousal/attention levels, infant cortisol levels, to cite but a few. Music in this context, she argues, is a medium for mood self-regulation of both mother and child, a medium that is then used by adolescents and adults as they progress to other types of music used for mood self-regulation

In the conclusion, Trehub summarizes some of her findings nicely: “It is clear that infants do not begin life with a blank musical state. Instead, they are predisposed to attend to the melodic contour and rhythmic patterning of sound sequences, whether music or speech. They are tuend to consonant patters, melodic as well as harmonic, and to metric rhythms. Surely these predispositions are consistent with a biological basis for music…” (p. 14)

Personally, I found the article very clear, well-written and convincing. I had never encountered so much information about infant’s musicial abilities, as well as mother’s singing research. This was a nice dove-tail with the Huron article questioning whether or not music is an evolutionary adapation.

An Introductory Perspective on Music Psychology - Eagle (HMP 1)

Eagle begins the first chapter of this handbook by stating, enthusiastically, that this text is written and edited by professionally trained musicians who are also scientists. This is refreshing, as some other texts on music psychology are written by people whose primary training is in psychology, leaving their music training as a secondary component of their education. After paying respect to “the father of Music Psychology” – Carl Seashore – Eagle describes his work on the CAIRSS project, an online database of articles from various journals relating to music psychology. (CAIRSS can be accessed at http://imr.utsa.edu/CAIRSS.html).

Eagle describes the field of music psychology as an interdisciplinary world, including aspects of fields such as education, sociology, anthropology, biology, philosophy and physics. This is certainly true from what I have seen, and this is one of the reasons I enjoy this field so much. Eagle presents an interesting, if dated, graphic based on a drawing of an atom to show relationships amongst various disciplines which study vibration and sound.

The next section of this chapter is divided into parts that review the past of the field, look at the present state of the field (at the time of the book’s publication in the late 90’s) and some projections about what the future may hold for music psychology. To review the past, textbooks are listed chronologically to give the reader an idea of what literature exists, and what time periods have been fruitful for the discipline. Periodicals are also discussed, and the CAIRSS project is again mentioned.

In his section for looking at the current state of music psychology, Eagle primarily explores, briefly, some of the journals that make current research accessible to other researchers and practitioners. When looking at what the future may hold for the discipline, Eagle’s enthusiasm becomes very apparent, making his writing seem more emotionally-driven. He discusses the development of theory and presents a triangular model of theory, practice and research, where each of those areas informs each of the others. Eagle seems to be seeking a theory that more succulently conjoins various elements throughout the field, alluding to Einstein’s E=mc^2 as an example of a theory which has done such. Metaphysics, time, soundscapes, altered states of consciousness… Eagle is truly zealous in his vision of a music psychology that encompasses music and related topics (see table 2, for example).

Eagle has succeeded in writing an inspiring overview of the past, present and possible future – albeit an extravagant one – of music psychology.

The social and applied psychology of music

Was there ever any doubt that music existed in a social context? I'm sure no educated person would debate the fact. I would be willing to go out on a limb however and say that current musical trends have desocialized music in several ways. North and Hargreaves address several examples including portable musical devices and the subsequent miniaturization thereof, downloading music, and programs that enable anyone to compose music. In contrast to previous musical trends, many of these devices allow the listener to isolate themselves. However, if I were to adopt Kuhn's paradigm shift and Huron's evolutionary adaptation ideas, perhaps I could view these developments as necessary survival/evolutionary advancements.

Nonetheless, whether one decides to view social and applied psychology from either perspective, it is evident that research and development in the field is constantly advancing and changing. Sub-disciplines of music psychology have developed including :

1) Sloboda's 1985 The Musical Mind that followed a more mainstream approach with links to neuroscience and computer science in the field of musical syntax, sight reading, and music memory (p. 2)

2) Hargreave's The Developmental Psychology of Music that focuses on informing educational policy through research in preschool and preference studies

Social psychology follows similar divisions by including:

1) macro sociology that include larger sociological institutions and trends

2) micro sociology that include interactional processes

These divisions all provide lines for research which don't seem to be crossed very often. Doise's 'Four levels of analysis' in social psychology is a good example of thes, viz:

1) Intraindividual analysis - investigates cognitive, perceptual, biological processes by which people organize their social environment eg. impact of personality on musical preference

2) Interindividual/situation analysis - eg. the use of body language in ensemble playing

3) Socio-positional analysis - relationships between individual eg. gender stereotyping regarding instrument choice

4) Ideological analysis - broad cultural systems of beliefs

According to North and Hargreaves, the predominant features of social psychology's approach includes Doise's 'Levels of analysis', topics based research, the application of research to 'real' world problems, and research into what music is actually used for.

P.s

The picture, if you're not familiar with it, is Kuhn's duck-rabbit optical illusion. I think it is a perfect representation of how anyone including researchers can view things from a different perspective - perhaps consider a cross-pollination of topics???

WEEK 2: Is music an evolutionary debate?

David Huron suggests some interesting perspectives on the role of evolution in music. His initial observation of the concept of evolution as both a physiological AND psychological attribute sparked my interest immediately. From a personal perspective, the theory of evolution as a physiological term is a concept that I have not entirely embraced however, the psychological evolution of man/woman is undeniable considering the adaptive qualities man has had to adopt with regard to his environment both socially and geographically.

The view that music is a form of nonadaptive pleasure-seeking (NAPS) is interesting but ill-founded in my opinion. It seems unlikely that so many cultures would adopt a musical approach in their everyday lives, that children would be encouraged to create music, and that adults would dedicate their lives to the pursuit of music if music was simply NAPS. Huron confirms my sentiments (p. 59) "nonadaptive pleasure-seeking behaviors tend to be short-lived" - which we know music is certainly NOT. His correlation between drug/alcohol abuse and its predisposition to inhibit survival is a perfect example of how music does not fall into the same category.

Several of the evolutionary theories of music viz. mate selection, social cohesion, group effort, perceptual development, motor skill development, conflict resolution, safe time passing, and transgernational communication are very relevant in modern times (even though adaptations based on observation of modern times should be avoided p. 65).

Huron's focus on the role of music as a form of social bonding seems indisputable. His initial thoughts on the correlation between Williams syndrome and Asperger autism and their consistent social and musical relationship (p. 69) is very enlightening. He goes on to reveal 'Happy Birthday' as the most popular song of all history, another example of music and social bonding. And of course, I believe every individual can provide a personal example of music's ability to alter hormones and enhance mood.

A complimentary addition to this chapter is Josh McDermott's essay on 'The evolution of music' Nature 453, 287-288 (15 May 2008) | doi:10.1038/453287a; Published online 14 May 2008.