Thumb-, Fingersucking and Bruxing Habits in Children Thumb- and fingersucking (and grinding habits) in infants and children have occupied the attention of many psychologists and psychiatrists for well over a hundred years.* Unfortunately, little knowledge of etiology and treatment is scientifically grounded in good experimental data. Treatment and etiology continue to be based on expert, and oftimes authoritarian polemics. Wolfenstein (1953) has reviewed and charted the course of advice given in the editions of the bulletin Infant Care which have appeared regularly since the first edition in 1914. She has charted how child health experts have emphasized or deemphasized the pernicious nature of thumbsucking over those years. Wolfenstein based her analyses on the bulletins appearing from 1914 to 1951; it would be interesting to examine the editions of the last 25 years to provide a picture of the childbearing practices in this area for almost 75 years. Initially, there were strong psychoanalytic interpretations of the meaning and treatment. These were subsequently superseded by learning theory formulations. Thumbsucking and fingersucking habits, in addition to receiving considerable attention by psychologists, have also received attention from dentists as a possible cause or contributor to malocclusions and deformities of the teeth and associated structures. Chandler (1878) felt that thumbsucking caused "considerable space to intervene between the upper and lower incisors, but the principal permanent irregularity that results from this habit is from its continuance after the eruption of the permanent teeth." Similar interpretations have continued since that time. Bruxing and grinding habits, however, seemed to have escaped the attention of most psychologists, at least in terms of the amount of literature available. In dentistry the literature has largely been confined to that dealing with adults who exhibit these habits, and until recently was very psychodynamically oriented. *Literature on sucking habits in animals is not reviewed in the present paper. However, the interested reader is referred to papers by Levy (1928, and 1934). Benjamin (1962a and 1962b) has reported studies of nonnutritive sucking and the development of malocclusions in rhesus monkeys. 8 Etiology and Development of Thumb- and Fingersucking The etiology of thumb- and fingersucking habits is unknown. number of investigators have indicated that sucking habits are reflexes whose precursors appear during intrauterine life as early as the fifth month (Hooker, 1942). Gessel (1954) concluded that the beginning of full swallowing and sucking was evident at the 32- to 36-week fetal stage with full maturation occurring in the last two months of fetal life. Extranutritive sucking activities appear to increase from three to about seven months and then spontaneously decrease in significance (Brazelton, 1956). Brazelton observed that the decrease was coincident with motor accomplishments such as creeping, crawling, and sitting. Of the 70 babies he followed, four continued rather intense extranutritive sucking into the second year and were considered problem suckers. Brazelton's definition of a problem sucker was "one who sucks his fingers beyond infancy to such an extent that it becomes a problem to his environment, hence to himself." With slight modification, this definition will be retained throughout this review. Crump, Gore, and Horton (1958) were interested in the development of the sucking reflex in premature infants and whether the response approximately paralleled that of other aspects of growth and development. They suggested that a premature infant of approximately 7.5 months gestation age could be expected to reach maturity at 45 days postnatally based on the assumption that the reflex is completely developed in full-term infants. In order to test their hypothesis they measured fluid intake (volume consumed in cc) per time unit intervals (in seconds) as an index of sucking power in 52 black female premature infants and 32 normal newborn black infants. During the first three days of life, the premature infants ingested water at a mean rate less than half that of the full-term baby. (0.24cc/sec. vs. 0.60cc/sec.). They did find that sucking efficiency increased with age with the heavier infants reaching maximal efficiency at 30 days. One of the activities which has been related to sucking behavior has been termed the "rooting reflex." If the infant's cheek is stimulated by an object such as a finger, the infant turns his head towards the stimulus and opens his mouth (Gentry and Aldrich, 1948), an activity which was first described by Samuel Pepys in 1667 and later by Blanton and Blanton (1927), Jensen (1932) and others. The rooting reflex is frequently accompanied by sucking movements and has been considered related in some fashion. The rooting reflex would appear to have adaptive value in that it would likely increase sucking and sucking opportunities particularly of a nutritive nature since sucking would occur whenever the lips were stimulated by the nipple. However, the findings of Gentry and Aldrich would suggest that sucking behavior increases the likelihood of the rooting reflex since they found that before sucking, the rooting reflex could not be elicited or there was considerable delay before it could be. Thus, using the rooting reflex as a variable in explaining the development of thumbsucking activities as some have done (Ayer and Gale, 1970; Gale and Ayer, 1969; Klackenberg, 1949) may not be quite so correct. The rooting reflex or directed head turning response has been studied most extensively by Prechtl (1958) from both a behavioral pattern and an underlying physiological mechanism approach. He has reported that the entire complex of infant feeding behavior disappears because of the integration of new functional complexes occurring with the development of the central nervous system. Of some interest too is the observation that grasping of the nipple during feeding is frequently disturbed by the rooting reflex (or directed head movements) which is usually corrected by the mother by grasping and fixing the head of the infant to receive the nipple. Prechtl has also reported that the response is inhibited by drowsiness and satiation, but facilitated by hunger. In addition, proprioceptive information appears important as demonstrated by positioning the child on its back facing upwards. In this position, the response is greater when the infant's arm on the stimulated side is held up and weaker when held down. Psychoanalytic and Learning Theory Models Ever since Freud (1938) indicated a belief that thumbsucking was a manifestation of infantile sexuality, controversy has reigned between psychoanalytically oriented proponents and learning theory proponents. On the basis of the psychoanalytic model, it was cautioned that persistent thumbsucking was a symptom of emotional disturbance (Kaplan, 1950; Kanner, 1950; Pearson, 1948; McDonald, 1963) and should not be treated without specific attention to the underlying psychological problems. spite of the voluminous amount of literature available, few studies support any of the psychoanalytic hypotheses regarding thumb- and fingersucking habits. In More recently, investigators have conceptualized thumb- and fingersucking habits in learning theory terms (Palermo, 1956) and the available evidence provides support for a learning theory approach to etiology and treatment of these habits (e.g., Benjamin, 1967; Davis, Sears, Miller and Brodbeck, 1948; Sears and Wise, 1950; Davidson, Haryett, Sandilands, and Hansen, 1967; Larsson, 1972; Baer, 1962; Graber, 1958). In summarizing the investigations to date, it can be determined that developmental approaches to studying the etiology of thumbsucking and fingersucking habits provide few clearcut answers to the question. Psychoanalytic approaches have been clearly unproductive, both for understanding etiology and for developing treatment modalities. theory explanations appear more relevant particularly in terms of providing effective treatment methods. Etiology is of less concern because of the assumptions made by learning theorists (see for example, London, 1964). Learning The Extent of the Problem Although the literature is not complete, it is useful to examine the few studies which have attempted to determine the prevalence of thumb- and fingersucking habits, in an effort to determine the extent of the problem. Estimates are difficult to obtain and even more difficult to interpret since they were frequently obtained in association with malocclusion, from small samples, etc. Traisman and Traisman (1958) observed 2650 infants and children from birth to 16 years and reported that about 46% of them had sucked their thumbs at some time during this period. Olson (1929) actually observed children in classrooms from 6 to 13 years of age and recorded oral habits as they were manifested. He estimated that 48% to 59% of the children in each classroom exhibited oral habits and concluded that oral habits were relatively stable across time. Although these estimates are probably accurate, it is important to note that his definition of oral habits included thumbsucking, nailbiting, fingersucking and protrusion of the tongue. Sears and Wise (1950) provide data from which it can be calculated that at the age of 2.5 years some 52% of their sample of 72 children exhibited thumband finger sucking habits. Kunst (1948) collected 28,000 behavioral samples on 143 infants confined to an orphanage during the first year of life. The study is remarkable for the enormous detail she provides on the relationships between thumb- and fingersucking activities and variables such as sex, time from last feeding, whether the infant was asleep or awake, the presence of attendants, teething, positioning of the infant, etc. Every infant that was observed exhibited thumb- or fingersucking behaviors at some time during the study. Most began sucking soon after birth and showed an increase in frequency during the first three months, followed by a plateau from the third to sixth month, a decline to the tenth month and then an increase through the twelfth month. Kunst also reported a slight but not significant increase during the period of eruption of the first primary teeth. Sucking during awake periods occurred considerably more than during sleep in the first few months of life; the reverse was true in the last months of the first year. Brazelton's (1956) findings are somewhat opposite to those of Kunst; however, he relied on reported observations by mothers and thus his findings are open to criticism. Figure 1 represents an attempt to determine the incidence of thumband fingersucking habits from data provided in several studies. As will be observed, there are wide variations in the estimates. Small sample sizes, and liberal and restricted definitions of sucking activities are probably responsible for some of the variations. |