“…These difficulties may have a negative impact on the formation of infant attachment security. However, researchers have questioned the validity of the traditional measure of infant attachment security, the strange situation, for use with children with developmental delay (Atkinson et al, 1999;van IJzendoorn, Goldberg, Kroonenberg, & Frenkel, 1992;Vaughn et al, 1994). The attachment Q-set (AQS; Waters, 1986;Waters & Dean, 1985) } the other instrument considered a valid measure of infant attachment security (van IJzendoorn, Vereijken, Bakermans-Kranenburg, & Riksen-Walraven, 2004) } has proved difficult to code reliably (cf.…”