We found that the percentage of melatonin suppression by light in children was almost twice that in adults, suggesting that melatonin is more sensitive to light in children than in adults at night.

Tryptophan can be metabolized via 5-hydroxytryptamineϭserotonin to melatonin by a series of 4 enzymes in pineal body. Lack of serotonin in body fluid in the brain during daytime can lead to several psychiatric disorders, while shortage of plasma-melatonin at night can be related to sleep disorders. The Morningness-Eveningness (M-E) questionnaire and the original questionnaire including questions on sleep habits, mental symptoms, and contents of meals were administered to 1055 infants aged 0-6 yrs, 751 students attending an elementary school, and 473 students attending junior high school in Kochi City (33°N). The index of tryptophan taken at breakfast (Trp-Index) was calculated as tryptophan amount per one meal based on the tryptophan included in each 100 g of the foods and a standard amount of food per one meal. A significant positive-correlation between M-E scores and Trp-Index was not shown by relatively older students, aged 9-15 yrs (Pearson's test, rϭ0. 044-0.123, pϭ0.071-0.505), whereas a significant positive correlation was shown by infants and young elementary school students aged 0-8 yrs (rϭ0.180, 0.258, pϽ0.001). The more frequently the infants had difficulty falling asleep at bedtime and waking up in the morning, the less the Trp-Indices taken at breakfast were (Kruskall-Wallis-test, pϭ0.027 for difficulty falling asleep; pϭ0.008 for difficulty waking up). The more frequently infants became angry even by a little trigger, or depressed, the lower (more evening-typed) the M-E scores were (Kruskal-Wallis test: pՅ0.001). Tryptophan ingested at breakfast is very important for children to keep a morning-type diurnal rhythm, high quality of sleep, and indirectly good mental health, presumably, through the metabolism of tryptophan to serotonin in daytime and further to melatonin at night.

The production of unstressed vowels in English by early and late Korean-and Japanese-English bilinguals was investigated. All groups were nativelike in having a lower fundamental frequency for unstressed as opposed to stressed vowels. Both Korean groups made less of an intensity difference between unstressed and stressed vowels than the native speakers (NSs) of English as well as less of a difference in duration between the two types of vowel than the NSs. The Japanese speakers, whose native language has a phonemic length distinction, produced more nativelike durational patterns. Finally, the vowel quality (first and second formant frequencies) of unstressed vowels was different from the NS group's for the late bilinguals, for whom unstressed vowels were widely dispersed in the vowel space according to their orthographic representations, and

The relationship of meal habits and alcohol/ cigarette consumption to circadian typology and sleep health in Japanese female students was studied from an epidemiological point of view. Questionnaires on Morningness-Eveningness by Torsvall and Åkerstedt (1980), sleep habits, regularity of meal intake and meal amount, and style of alcohol and cigarette consumption were administered to 800 students aged 18-29 years, attending university or training schools for nutrition specialists (Aichi Prefecture, 35°N). Points from ten questions were totaled to provide estimates of sleep habits given as the Unhealthy Sleep Index (UHSI). The average and standard deviation of Morningness-Eveningness scores were 16.07Ϯ3.53. Students who had breakfast at regular times showed significantly higher Morningness-Eveningness scores than those who ate at irregular times. Based on an integrated analysis (ANOVA) on the effect of regularity of breakfast intake on sleep health, regular breakfast intake may link to sleep health positively via the shifting to morning-type (i.e., the phase-advance of the circadian clock). However, a similar analysis promoted the hypothesis that alcohol consumption and cigarette smoking relate to sleep health negatively and directly, rather than via the shifting to evening-type (i.e., the phase-delaying of the circadian clock). In the case of young women, getting a good quality and quantity of sleep in normal life seems to be important for promoting their mental health, which may fluctuate throughout the menstruation cycle accompanied by mental symptoms as a part of premenstrual syndrome.

2003) found that three factors affect English speakers' stress placement on bisyllabic non-words: syllabic structure, lexical class and stress patterns of phonologically similar real words. The current replication and extension included three groups (N = 30): native English speakers, early Spanish-English bilinguals, and late Spanish-English bilinguals. Participants produced and gave perceptual judgments on 40 non-words of varying syllabic structures in noun and verb sentence frames. A regression analysis used the three factors to predict stress placement in production and perception. All three groups showed significant effects from stress patterns of phonologically similar real words and lexical class. The effect of syllabic structure for early bilinguals was slightly different from that of native speakers and late bilinguals showed greatly reduced effects. Late bilinguals exhibited more initial stress overall, possibly due to L1 transfer. These results run counter to the prediction made by Long (1990) about age effects on phonological acquisition.