Developmental normative data for 775 children aged 6-16 are presented for the Test of Variables of Attention (T.O.V.A.), a 23-minute fixed-interval visual Continuous Performance Test with minimal language demands and no left-right discrimination. The target is presented on 22.5% and 77.5% of the trials during the first and second halves, respectively, T.O.V.A. indices include omission and commission errors, response time means and standard deviations, and anticipatory responses. Attention and impulse control developed in a non-linear manner, changing rapidly in early childhood and leveling off during later childhood and adolescence.

Lymphocytes, from randomly selected individuals having normal immune function, when incubated in vitro with varying concentrations of streptococcal antigens, responded in three ways: (a) response over the entire antigen concentration range, i.e., responders; (b) low response to only the highest antigen concentrations; and (c) no response at any antigen concentration. Frequency distribution analysis of these groups indicated that a significant association occurred between the ability to respond and HL-A 5.

No abstract

The authors would like to thank the teachers of the Elk Grove School District for their participation in this study. Special thanks are extended to Lawrence Harper for his helpful comments and donation of the electrical timing devices. In addition, the time volunteered by observers Robin Hansen and Carol Berkenkotter is greatly appreciated.2 Requests for reprints should be sent to

A B S T R A C T INTRODUCTIONOne of the few seemingly well-established facts about the etiology of insulin-dependent diabetes mellitus (IDDM)l is that extensive heterogeneity is present (1-8). Thus, several genetic mechanisms are likely to be involved. These may possibly range from multigenic (with each locus contributing only a small effect) to the major genetic effect of Mendelian modes of inheritance. The recent reports of association between the histocompatibility system (HLA) and IDDM (5,6) indicate a direct and important effect of the HLA antigens on the risk of the disease. One possible explanation of this association is linkage between the two traits; we have conducted a series of linkage analysis studies to examine these possibilities. Genetic studies of IDDM must be designed to answer a specific research question under circumstances that minimize the "noise" of heterogeneity. We have, therefore, sampled multiplex families (i.e., those families with