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Tears and crying as a genuine expression of human feelings have aroused the attention of artists and literati for many centuries, but the medical principles have only received little attention for a long time. In this article the developing explanation and the various interpretations of this phenomenon will be demonstrated in combination with their dependence on the respective knowledge of anatomy and physiology. The antique conception of the lacrimal apparatus and the significance of tears in the Middle and Baroque Ages with respect to the history of salvation will also be discussed as well as the search for the lacrimal organ and the mechanical interpretation of lacrimation in the seventeenth and eighteenth centuries. Moreover, the discussion on the benefits and disadvantages of tears will be followed and the new turn which led to the explanation of the phenomenon under the influence of the theory of evolution will be emphasized.

Emotional tears, an exclusively human means of communication, are complex and rarely the subject of scientific research. The same nerves, receptors, and transmitters seem to be involved in their production as those used for basal and reflex tears. However, stimuli must be received in a cognitive/social context, detected by "induction centers" in the telencephalon, and forwarded to effector centers. Increased concentrations of protein, prolactin, manganese, potassium, and serotonin have been detected in emotional tears. Various theories try to explain the reason for and benefit of emotional tears. A number of factors, such as ethnic group, social status, profession, hormonal situation, gender, and individual threshold, influence whether an individual is a "crier" or a "noncrier." Manipulative tears are a strong weapon for unbalancing other people, and the expression "crocodile tears" is used for both manipulative tears and aberrant gustolacrimal tears. Pathological crying occurs during depression, but it also occurs in the context of central nervous system disease as prolonged crying fits without cause or emotion. Absent emotional tearing is observed in congenital, often syndromal, disorders.

Subjective and auditory assessment of the voice is now more commonly being replaced by objective voice analysis. Because of the amount of data available from computer-aided voice analysis, subjective selection and interpretation of single data sets remain a matter of experience of the individual investigator. Since neuronal networks are widely used in telecommunication and speech recognition, we applied self-organizing Kohonen networks to classify voice patterns. In the phase of "learning," the Kohonen map is adapted to patterns of the primary signals obtained. If, in the phase of using the map, the input signal hits the field of the primary signals, it will resemble them closely. In this study, we recorded newborn and young infant cries using a DAT recorder and a high-quality microphone. The cries were elicited by wearing uncomfortable headphones ("cries of discomfort"). Spectrographic characteristics of the cries were classified by 20-step bark spectra and then applied to the neuronal networks. It was possible to recognize similarities of different cries of the same children and interindividual differences, as well as cries of children with profound hearing loss. In addition, delayed auditory feedback at 80 dB SL was presented to 27 children via headphone using a three-headed tape-recorder as a model for induced individual cry changes. However, it was not possible to classify short-term changes as in a delayed feedback procedure. Nevertheless, neuronal networks may be helpful as an additional tool in spectrographic voice analysis.

Equipment for near-infrared laserspectroscopy for clinical application is newly available. By this technique noninvasive monitoring of biochemical parameters is achievable. We report on our first experience with a Radiometer prototype for such NIR laserspectroscopy during measurements in 5 neonates. Laserdiodes provide emission at a wavelength of 775, 805, 845 and 904 nm. The registered signals are computerized aiming at a calculation of relative changes of saturated and unsaturated hemoglobine, changes in blood volume and cytochrome aa-3. In this article graphical display of the parameters give insights in the redoxstate and the hemodynamics of the biological sample. The near-infrared laserspectroscopy has the potential of becoming an instrument for the study of biophysical and biochemical alterations in the newborn.

The different types of crying which can be observed in the healthy and in the sick infant are described. Recent findings on behavioral and electrophysiological research are reviewed which led to a better understanding of the characteristics and possible causes of the different crying behaviors as well as of the effectiveness of therapeutical interventions.