uro ps ych iat rist ▁Eric ▁K and el , ▁future ▁recip ient ▁of ▁the ▁ 2 0 0 0 ▁Nobel ▁Prize ▁in ▁Phys i ology ▁or ▁Medicine . ▁They ▁married ▁in ▁ 1 9 5 6 ▁and ▁had ▁two ▁children . ▁ ▁Scient ific ▁work ▁ ▁When ▁in ▁the ▁ 1 9 6 0 s ▁research ▁on ▁drug ▁mis use ▁gained ▁in ▁importance , ▁K and el ▁applied ▁to ▁join ▁a ▁research ▁team ▁that ▁intended ▁to ▁investigate ▁drug ▁use ▁among ▁high ▁school ▁students . ▁She ▁assumed ▁she ▁could ▁contribute ▁with ▁her ▁research ▁experience ▁concerning ▁the ▁influence ▁of ▁parents ▁and ▁peer ▁groups ▁on ▁ad oles c ents . ▁However , ▁she ▁was ▁rejected , ▁because ▁she ▁wanted ▁to ▁interview ▁both ▁parents ▁and ▁students , ▁and ▁the ▁research ▁team ▁fe ared ▁that ▁this ▁might ▁und erm ine ▁students ' ▁co operation . ▁K and el ▁developed ▁her ▁own ▁research ▁project , ▁which ▁ultimately ▁led ▁to ▁an ▁influ ential ▁longitud inal ▁study ▁of ▁ 1 , 3 2 5 ▁persons . ▁Later , ▁she ▁considered ▁this ▁work ▁as ▁a ▁turning ▁point ▁in ▁her ▁career . ▁ ▁The ▁main ▁subject ▁of ▁this ▁and ▁further ▁similar ▁investig ations ▁was ▁the ▁sequence ▁of ▁first - time ▁use ▁of ▁various ▁legal ▁and ▁illegal ▁dru gs . ▁Her ▁research ▁in ▁this ▁area ▁found ▁a ▁strong ▁reson ance ▁in ▁scientific ▁and ▁political ▁discuss ions , ▁and ▁the ▁catch phr ases ▁" ste pping - stone ▁theory " ▁( used ▁since ▁the ▁ 1 9 3 0 s ) ▁and ▁" gate