David Hay 
Why Spirituality is Difficult for Westeners [PDF ebook] 

Dr Hay is Honorary Senior Research Fellow at the University of Aberdeen. A zoologist by profession, his research has been guided by the hypothesis that religious or spiritual awareness is biologically natural to the human species and has been selected for in the process of organic evolution because it has survival value. Although naturalistic, this hypothesis is not intended to be reductionist with regard to religion. Nevertheless it does imply that all people, including those who have no religious belief, have a spiritual life. His research has included a number of national and in-depth surveys of reports of religious or spiritual experience in the United Kingdom.