Complex sentence: While general knowledge is supported by semantic memory, autobiographical knowledge is supported by episodic memory, which is not tested in intelligence tests and tends to be difficult to measure because of the uniquely personal nature of such memories.
Split into simpler sentences: While general knowledge is supported by semantic memory, autobiographical knowledge is supported by episodic memory. Episodic memory is not tested in intelligence tests and tends to be difficult to measure because of the uniquely personal nature of such memories.