Inattention is partially independent of modality. In contrast, response inhibition is modality-specific. Although ADHD is defined regardless of modality, hyperactive students may exhibit deficits in the auditory modality but not in the visual modality or vice versa.

Handedness is associated with cerebral hemispheric differences. Normal patterns of brain asymmetries are needed for the neural processing of attention. In order to identify ADHD (Attention Deficit Hyperactive Disorder) children, the use of checklists allows a greater level of accuracy. Here, we will review our data on this subject. Our first study investigated the psychometric properties of a scale developed to assess attention disorders. Our second study investigated the relationship between handedness and attention disorders using the factors derived from the scale. Our third study included the use of a continuous visual test of attention (CVAT) and examined the relationship between handedness and CVAT variables. For the first and second study, 239 students were included. From this sample, 42 students were selected to participate in the third study. Forty-five teachers rated the children. Four factors were extracted: hyperactivity/impulsivity (explained variance = 36.3%); inattention (11.4%); social isolation (5.2%) and self-confidence (explained variance = 3.3%). Sixty-eight children were included in the ADHD group. We found a higher number of consistent left-handers in the ADHD group as compared to the normal group and a significant effect of handedness on factor hyperactivity/impulsivity. This indicated that left-handers showed greater problems in the hyperactivity-impulsivity domain as compared to right-handers. Considering the data derived from CVAT, a significant handedness effect was found only for the variable commission errors. Left-handers with attention problems showed the greatest number of errors and normal dextrals the lowest number of errors. Normal left-handers made significantly more errors than normal dextrals. Commission error is a parameter that is commonly viewed as a measure of impulsivity. Our data show that hyperactivity/impulsivity is related to handedness, because left-handers present more problems in impulsive behavior than right-handers and suggest that consistent left-handed subjects show greater probability to develop ADHD as compared to right-handed subjects.

In spite of the fact that the legal system adopted in Brazil is codified on the Roman tradition, there is no specific protection in law for people suffering from Attention Deficit Disorder (ADD). In contrast, the law of the United States is largely derived from the common law system and there are two federal laws that guarantee a free appropriate public education and provide services to eligible students with disabilities. They are: Section 504 and Individuals with Disabilities Education Act2. The American Legal System reflects the social demand based on epidemiological studies. In the present investigation, we studied the prevalence of attention disorders in Brazil. The sample included 239 students, rated regarding attention problems with a checklist filled by 45 different teachers. As left-handers show greater problems in the impulsive-hyperactivity domain, we investigated the influence of gender on attention problems using handedness as a covariate. Hand preference was assessed by direct observation. A student was classified into the ADD group if he (she) was rated maximum score in at least six questions concerning impulsivity, hyperactivity, and inattention. Sixty-eight students (28% of the total sample) were included in the ADD group. The percentage of males was found to be greater in ADD group as compared to the percentage of males in the normal-control group. The gender effect was not explained by handedness. Our data is similar with other studies. For instance, the rate of ADD symptoms among indigenous students from the Brazilian Amazon was found to be 24.5%. In Brazilian juvenile offenders, the percentage was 33%. The differences with other studies are discussed considering sampling procedures. In accordance with the tradition of the Roman system, we urgently need Federal specific laws to deal with this public health problem. We must convert into specific laws, the Convention on the Rights of Persons with Disabilities (United Nations) that was recently ratified in Brazil.