Sir: The apparent connection between dummies and low IQ (report, 19 April) is susceptible to a simple explanation. Until recently, dummies were regarded as unhygienic and teeth- deforming, setting up expectations of instant gratification in the child and a lazy expedient for the mother. Thus, only stupid mothers gave them to their babies. Such mothers might reasonably be expected to produce a higher number of low-IQ children. Now that dummies have been rendered respectable by the childcare gurus, and are given to their babies by highly intelligent professional women, it would not be surprising to find, in 20 years' time, that such babies had higher IQ scores than others.