This thesis examines the extent to which a specific learning intervention programme, based on specific early science skill development may increase development in thinking in a particular early childhood sample. The background literature has focused on Piaget's and Vygotsky's theories of cognitive development as they relate to the intervention programme and the age group of the participants in this research study. The review discusses the need to teach thinking and the relevant literature on the intervention programme is critically reviewed. This research study, undertaken in and adapted for an Irish primary school, involved a sample of forty four participants aged between four and six years old. An intervention group of twenty pupils participated in the learning intervention Lets Think!-Early Years programme – based on the theory of cognitive acceleration. The learning intervention programme consisted of fifteen lessons based on the early science skills of classification, seriation and causality. The remainder of the group were the non-intervention group. All participants underwent three pre and post intervention tests and completed a pupil questionnaire. Local teachers completed a teacher questionnaire on questions relating to the research question and this combined with the researcher's observations recorded in a reflective journal provided the data to be analysed. A comparative analysis of responses obtained from the above tests, questionnaires and reflective journal, suggest that pupils from the intervention group displayed a greater improvement in their thinking ability in comparison to the nonintervention group, with the factors of gender and age of the pupils having a significant effect. This finding indicates that a cognitive intervention programme through science may have a significant immediate and positive effect on the rate of the early year's pupil's cognitive development.