Research based on data from longitudinal studies, such as the National Institute of Child Health and Human Development Study of Early Child Care and the Minnesota Study of Risk and Adaption from Birth to Adulthood, and from cross-sectional studies, consistently shows associations between early attachment classifications and peer relationships as to both quantity and quality. Lyons-Ruth, for example, found that 'for each additional withdrawing behavior displayed by mothers in relation to their infant's attachment cues in the Strange Situation Procedure, the likelihood of clinical referral by service providers was increased by 50%.'