Larger capacity for unconscious versus conscious episodic memory

Episodic memory is the memory for experienced events. A peak competence of
episodic memory is the mental combination of events to infer
commonalities. Inferring commonalities may proceed with and without
consciousness of events. Yet, what distinguishes conscious from
unconscious inference? This question inspired nine experiments that
featured strongly and weakly masked cartoon clips presented for
unconscious and conscious inference. Each clip featured a scene with a
visually impenetrable hiding place. Five animals crossed the scene
one-by-one consecutively. One animal trajectory represented one event. The
animals moved through the hiding place, where they might linger or not.
Participants’ task was to observe the animals’ entrances and exits to
maintain a mental record of which animals hid simultaneously. We
manipulated information load to explore capacity limits. Memory of
inferences was tested immediately, 3.5 or 6 minutes following encoding.
Participants retrieved inferences well when encoding was conscious. When
encoding was unconscious, participants needed to respond intuitively. Only
habitually intuitive decision-makers exhibited a significant delayed
retrieval of inferences drawn unconsciously. Their unconscious retrieval
performance did not drop significantly with increasing information load,
while conscious retrieval performance dropped significantly. A working
memory network, including hippocampus, was activated during both conscious
and unconscious inference and correlated with retrieval success. An
episodic retrieval network, including hippocampus, was activated during
both conscious and unconscious retrieval of inferences and correlated with
retrieval success. Only conscious encoding/retrieval recruited additional
brain regions outside these networks. Hence, levels of consciousness
influenced the memories’ behavioral impact, memory capacity, and the
neural representational code.