According to the definition of the report Children and Clinical Research by the Nuffield Council on Bioethics (NCOB) (2015), there are significant differences in the concept of ‘childhood’ in relation to the capacity of minors to give consent. According to the report, it is not sufficient to simply differentiate between age groups in order to anticipate the ability to give consent. Rather, the interplay of cognitive, intellectual and emotional developmental processes in minors, with which they are confronted when facing complex decisions under time- and situation-dependent conditions, is decisive.
With this in mind, the NCOB has defined three different stages of decision-making ability in minors:

Stage 1:

Stage 1: Children and adolescents who are not capable of forming a qualified judgement about whether they wish to participate in medical research. In this case, minors are able to express emotional and affective reactions to the research process, but are not able to make an informed decision about their participation.

Stage 2:

Children and adolescents who have the ability to develop differentiated wishes and preferences, but are not willing or able to make a qualified assessment of the content, benefits and risks of participating in a study independently - i.e. without support. In these cases, an individual assessment is required of the extent to which the intrinsically formed wishes and aversions can be considered qualified. Regardless of this, supportive guidance from legal guardians and medical professionals is essential.

Stage 3:

 Minors who already have the intellectual and emotional maturity to make informed decisions. They are able to recognise and assess both the conditions and content of the respective research as well as its potential risks and future consequences. These persons are considered capable of making decisions, but remain legally minors and therefore in need of protection.

The stages of decision-making ability described do not always correlate with a person's age and can develop differently from person to person. They are hence not necessarily linear. This definition is therefore intended to provide practitioners with guidance on how to adequately assess the capacity of minors to give consent, irrespective of a mere focus on age.