Ace the EPPP 2025 – Power Up Your Psychology Practice!

The average reported correlation coefficient for identical twins reared together in relation to IQ is considered to be around .85. This high correlation suggests a significant genetic influence on intelligence since identical twins share nearly 100% of their genetic material. This finding highlights the role of heredity in cognitive abilities, indicating that environmental factors also play a role, but the strong correlation points to a substantial genetic component.

The other correlation values reflect different relationships. For instance, a correlation of .40 would imply a moderate influence of genetics, which does not align with the strong genetic basis suggested by the .85 value for identical twins. Similarly, a correlation of .68, while indicating a connection, is still lower than the consensus for identical twins, demonstrating that shared genetics in this context exert a stronger effect. Lastly, a correlation of .18 would indicate a very weak relationship, which does not apply to identical twins studied together and suggests minimal genetic influence, contrary to what empirical studies have shown.