Introduction 5 9 23 8 33 34 19 6 5 12 14 18 20 22 24 26 27 31 32 15 5 10 17 6 21 23 More knowledge on the expression and stability of problem behaviors before the age of 18 months would be advantageous, especially for doctors and nurses working in well baby clinics. In the Netherlands, infants visit well baby clinics according to a fixed scheme. At 14 months there is a relatively extensive check up. Since this is a moment for vaccination the attendance rate for this check up is high. Therefore, more knowledge on problem behaviors at especially 14-month-old was desirable. The current study was designed to investigate behaviors at this young age and had the following aims. The first aim was to examine the occurrence of problem behaviors or lack of competences at younger age that are considered to be psychopathological in later childhood. A second aim was to examine whether the constructs of problem behaviors and competences usually found in older children are already present at 14 and 19 months of age. A third aim was to examine the short-term stability of parent-reported problem behavior and lack of competences between age 14 and 19 months. To achieve these aims, we used a questionnaire with 55 items on mainly externalizing and social communication behaviors. Method Sampling N t 1 25 2 P 2 P 2 P 2 P N t 2 ) N N N Description of participants Approximately 88% of the parents were Dutch, 1.3% were Turkish, 1.8% were Moroccan, 1.3% were from the Caribbean (Surinam or the Dutch Antilles), 0.4% were from other Western countries, and 0.5% were of non-Western origin. Questionnaires were completed by mothers (80.5%), fathers (10.7%), and by both (0.6%). Mean child age was 14.80 months (SD = 1.84). The mean number of children in the family was 1.80 (SD = 1.03). Mean birth weight was 3,537.5 g (SD = 823.9). Of all infants, 1% had a physical or mental disability, 4.1% had a physical disease, and 6.3% used medication. Parental education level varied: 43.8% had a high level of education, 38.1% had a medium level of education, and 15.5% had a low level of education. Measures Behavior problem questionnaire 1 7 29 30 Data analyses 18 13 2 4 d d d d 11 Results Frequencies 1 Table 1 Common and uncommon problem behavior at 14 months  % With score 1 (sometimes) % With score 2 (often) % With score 1 or 2 Common problem behavior a 61.9 26.0 87.9 a 63.5 9.6 73.1   Demands must be met 56.8 14.1 70.9   Can’t stand waiting, wants everything now 51.1 16.2 67.3 a 35.2 29.8 65.0   Wants a lot of attention 50.3 14.4 64.7   Accident prone 56.4 6.4 62.8   Stays close to parent 54.0 4.5 58.5   Easily upset 46.3 7.5 53.8 a 39.4 14.0 53.4 a 46.1 5.9 52.0   Doesn’t keep trying 46.7 5.1 51.8 a 40.0 11.0 51.0 Uncommon problem behavior   Fails to follow with eyes 8.0 1.4 9.4   Doesn’t show interest in new objects 7.1 0.6 7.7   Doesn’t make happy noises 6.7 0.8 7.5   Doesn’t make noises spontaneously 5.8 1.1 6.9   Has less fun than others 4.5 1.5 6.0 a 5.3 0.6 5.9   Seems unhappy without good reason 4.9 0.7 5.6 a 4.3 0.9 5.2 Note a P Factor structure of problem behavior The principal component analysis with varimax rotation with eigenvalues >1.5 for two equally sized split half samples resulted in two very similar solutions. The scree test suggested a seven-factor PCA solution (eigenvalue >1.5) with a percentage explained variance of 34.6% (see Appendix to this paper for details). The PCA for the 19-month-old children showed the same factors as the analysis at 14 months, with 37.7% of explained variance. Five of the 55 items had higher loadings at 19 months on other factors than at 14 months. 2a r r Table 2 Pearson correlation matrix of factor sumscores of (a) 14-month-old and (b) 14- and 19-month-old Questionnaire domains Oppositional behavior Language development Attention Explorative behavior Communicative intent Dysregulation Inhibition 14 months a Oppositional behavior 1       Language development −0.001 1      Attention 0.522** 0.106** 1     Explorative behavior 0.005 0.412** 0.167** 1    Communicative intent 0.102** 0.422** 0.142** 0.351** 1   Dysregulation 0.436** 0.022 0.315 0.060** 0.124** 1  Inhibition 0.379** 0.098** 0.235** 0.076** 0.308** 0.308** 1 14 months 19 months b Oppositional behavior 0.678       Language development 0.029 0.476**      Attention 0.498** 0.112** 0.625**     Explorative behavior 0.089 0.264** 0.188** 0.452**    Communicative intent 0.057** 0.255** 0.131** 0.206** 0.466**   Dysregulation 0.353** 0.069** 0.300** 0.080** 0.127** 0.445**  Inhibition 0.306** 0.100** 0.247** 0.086** 0.120** 0.226** 0.380 Note **Correlation is significant at the 0.01 level (2-tailed) F P F P F P F P F P d d d d Stability over 5 months 2b 3 1 Table 3 t 1 t 2 t 1 t 2 N Behavioral dimension t 1 t 2 t 1 t 2 t 1 t 2 Oppositional behavior 0.37 0.42 44.8 60.3 Language development 0.47 0.44 31.3 55.8 Explorative behavior 0.42 0.44 34.2 50.3 Attention 0.42 0.42 45.0 56.7 Inhibition 0.64 0.65 29.0 43.7 Communicative intent 0.50 0.92 46.8 51.3 Dysregulation 0.73 0.35 27.5 51.1 Note t 1 t 2 Fig. 1 Transitions (expressed as percentages of children) between 14 months and 19 months for the 90th and 75th percentile cutoff of the total problem behavior score  Discussion 18 6 18 18 23 3 4 1 28 16 4 1 29 30 7 4 5 9 18 14 27 4 4 21 23 Limitations 8 18 Clinical implications This study underlines the growing need to identify problem behavior in early development. A better understanding of what is normal and abnormal in early infant-toddler development is of great value for the recognition of early psychopathology. Normative data for the prevalence and stability of behavior problems of 1- and 2-year-old children in a normal population may make it possible to provide early effective preventive intervention programs, in addition to background information for clinicians and researchers in order to develop such programs. In summary, externalizing behaviors were the most common, and social communication the least common, problems reported in a population sample of 14-month-old children. Boys were reported to show significantly more problems of externalizing behavior and competences. These behaviors were moderately stable over a 5-month period, between the ages of 14 and 19 months.