text: Prevalence of attachments to pacifiers and their psychological functions
  In the late 1960s researchers dispelled the notion that pacifiers were psychologically unhealthy and aberrant. Richard H. Passman and Jane S. Halonen at the University of Wisconsin-Milwaukee traced the developmental course of attachments to pacifiers and provided norms. They found that 66% of their sample of babies who were three months old in the United States demonstrated at least some attachment, according to their mothers. At six months of age, this incidence was 40%, and at nine months it was 44%. Thereafter, the rate of attachment to pacifiers dropped precipitously until, at 24 months of age and later, it was quite rare.
  These researchers also provided experimental support for what were then only anecdotal observations that pacifiers do indeed pacify babies. In an unfamiliar playroom, one-year-old toddlers accompanied by their pacifier evidenced more play and demonstrated less distress than did babies without them. The investigators concluded that pacifiers should be considered to be attachment objects, similar to other security objects like blankets.
  Passman and Halonen contended that the widespread occurrence of attachments to pacifiers as well as their importance as security objects should reassure parents that they are a normal part of development for a majority of infants and toddlers.