Based on the residual plot below, you will conclude that there might be a violation of which of the following assumptions? 
Definitions:
Courtship
The period in a couple's relationship which precedes their engagement and marriage, characterized by various social activities.
Mating
The process by which organisms pair and reproduce, often involving complex behaviors in animals.
Behavioral-Genetic Studies
Research that examines the role of genetic and environmental influences on behaviors.
Heritability
The proportion of observed variation in a particular trait that can be attributed to inherited genetic factors in contrast to environmental ones.
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