The habituation of higher-order conscious processes: Evidence from mental arithmetic

A recurring idea in psychology is that one is conscious only of the "outputs" of mental operations, but not of the operations themselves. Often, such "entry into consciousness" occurs involuntarily. To investigate involuntary entry, some experimentalists have used the reflexive imagery task (RIT). The RIT has revealed that, under certain conditions, external stimuli (e.g., line drawings) can elicit involuntary entry of high-level cognitions. In the basic version of the task, participants are presented with visual objects and instructed not to subvocalize (i.e., say in one's head) the names of these objects. Participants cannot suppress these subvocalizations on a majority of the trials. It has been proposed that, if RIT effects resemble a reflex, then perhaps they will habituate as reflexes do. In the "habituation" variant of the RIT, the same stimulus object (e.g., CAT) is presented on ten consecutive trials (ten "instantiations"), in order to induce habituation (i.e., a weakened RIT effect). It remains unknown whether such habituation effects arise for stimulus-elicited processes that depend, not on subvocalization, but on more complex processes, such as mental arithmetic. To illuminate this issue, we conducted a conceptual replication of the "habituation" RIT that involves, on each trial, the participant trying not to add two numbers (e.g., 14 and 2). We assessed whether the habituation effects were stimulus-specific or set-specific. Understanding the boundary conditions of the RIT effect and its habituation illuminates the limits of unconscious processes and the role of conscious processing.