Answer:
- 'Genetics; higher.'
Step-by-step explanation:
Adoption studies primarily aim to study the effect of different factors like genetic(nature) or environmental factors(nurture) on the behavioral or characteristics traits of a person.
As per the question, in case of a disorder being affected by 'genetics' then the researchers would view it as having the 'higher' chances of the 'disorder' being carried among the biological relatives as compared to adoptive relatives. They believe that genetic features or disorder which are more a product of biological association and thus, would impact the biological relatives.