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We examined the distribution of non-B27 alleles of the HLA-B locus among B27+ patients with ankylosing spondylitis (AS), to detect any additional HLA-B locus allele(s) that may act in conjunction with B27 to increase susceptibility to AS. HLA-Bw60 (or B40 when the Bw60,61 split of B40 was not typed for) was shown to be increased among B27+ AS patients in each of 5 independent data sets. This increase was statistically significant in 4 of the 5 data sets studied, and the overall significance was P less than 0.00001. Susceptibility to AS in B27+ individuals was further increased by a factor of approximately 3 when Bw60 was also present. The distribution of HLA-A alleles on the B27-bearing haplotypes in AS patients was not significantly different from that in normal controls. On the other hand, the distribution of HLA-A alleles on Bw60-bearing haplotypes was significantly different from the distribution of A alleles on Bw60 haplotypes in the general population (P less than 0.0005). Bw60 was not increased in B27- patients with AS. A dominant mode of inheritance generally fits AS; however, our sib pair analysis indicates that the B27,Bw60 disease subgroup follows a more recessive mode of inheritance.

Comprehension monitoring skills of younger (5- to 6-yr-old) and older (8- to 9-yr-old) children were compared. Children examined ambiguous and incomplete pictorial instructions as to how to make two models, and were asked whether there was anything else they would need to know in order to make the models. Questions were answered, and their oral instructions recorded. Both age groups were equally likely to judge the instructions to be incomplete, but the younger children were apparently less able to recognise their lack of understanding. Differences found were taken as evidence of more active and detailed processing of the instructions by the older children.

Relationships between 5- and 7-year-old children's communicative performance, and their level of understanding about message ambiguity and communication failure, were examined in three investigations. Communicative performance was assessed in terms of quality of instructions given for constructing a Lego model or a picture from felt pieces. The child speaker instructed the experimenter (Investigations 1 and 2) or another child (Investigation 3). Level of understanding about communication was assessed by asking the child to ascribe blame for communication failure following an ambiguous message, and to judge whether the speaker had told enough. In all three investigations, children with more advanced understanding about communication gave more detailed descriptions of pieces needed and supplied more information about positioning of pieces. In addition, in the first investigation those more advanced in understanding gave their instructions in a sequence more suitable for building. In the third investigation, child pairs more advanced in understanding communicated more effectively. It was suggested that the close association between communicative performance and understanding about communication occurred because the social experience which advances understanding, namely, the giving of explicit information when and/or why a listener fails to understand what the speaker means, at the same time encourages the child speaker to take responsibility for conveying a particular meaning unambiguously: the same experiences modify both communicative behavior and understanding about communication.