Dual-process theories have much to recommend them in the study of memory, as elsewhere in psychology (Anderson & Bower Reference Anderson and Bower1972; Jacoby Reference Jacoby1991; Mandler Reference Mandler1980; Yonelinas Reference Yonelinas2002). One particular version of dual-process theory has come to dominate both psychological and neuroscientific thinking: the distinction between recollection and familiarity. Ordinarily, we think of remembering as a full-fledged, conscious recollection, including the time and place at which the event took place and some reference to the person's role as agent, patient, stimulus, or experiencer. But another retrieval process, generally known as “familiarity,” lacks all of these accoutrements: there is just the event itself, absent any spatiotemporal or personal context, shimmering in the mind, feeling somehow familiar. In the target article, Bastin et al. have done an excellent job in summarizing the neural substrates of these two recollective experiences, and their integrative model seems both comprehensive and persuasive.

Identifying the neural substrates of mental functions depends critically on the availability of an accurate description of the functions themselves. In that sense, at least, cognitive (and social and affective) neuroscience depends critically on cognitive (and social and affective) psychology. “An analysis at the behavioral level lays the foundation for an analysis at the neural level. Without this foundation, there can be no meaningful contribution from the neural level” (Gallistel Reference Gallistel1999, p. 843; see also Coltheart Reference Coltheart2006; Hatfield Reference Hatfield2000; Kihlstrom Reference Kihlstrom2010). So the question remains whether the dualism of recollection and familiarity exhausts the forms that memory retrieval can take.

This may not be the case. For example, one of the most important contributions to dual-process theories of memory was a paper by Tulving (Reference Tulving1985), which distinguished between two forms of memory retrieval: “remembering” that an event occurred, as a full-blown episodic memory, and “knowing” that it happened, somewhat on the order of semantic memory. Rather quickly, “remembering” was relabeled as “recollection,” while “knowing” was reinterpreted in terms of familiarity, similar to priming or implicit memory (e.g., Gardiner Reference Gardiner1988; Yonelinas Reference Yonelinas2002); but in both formulations “knowing” was a residual category: any memory not classified as “remembered” was perforce classified as “known.” As a consequence, “knowing” may include a variety of distinct recollective experiences, each of which may have its own separate neural substrate.

In fact, evidence from a variant on the “remember/know” paradigm shows that there is more than one alternative to remembering an event (Kihlstrom, Reference Kihlstromin press). We can have abstract knowledge that an event occurred, in the absence of conscious recollection of its environmental and personal context, much as we know where we were born without actually remembering it. Or we can have an intuitive feeling that something is familiar, the way someone's face or voice can “ring a bell” at a cocktail party, even though we cannot remember the person's name or the circumstances under which we might have previously met him or her. In these ways, recognition-by-knowing can be distinguished from recognition-by-feeling in much the same way as, in the traditional remember/know paradigm, recognition-by-remembering can be distinguished from recognition-without-remembering.

Reports of “knowing” are more likely to occur following deep semantic processing, whereas reports of “feeling” are more likely to occur following shallow, phonemic processing. Recognition-by-knowing is associated with higher confidence ratings than recognition-by-feeling, while recognition-by-feeling is increased when subjects are encouraged to adopt a liberal criterion for item recognition. Recognition-by-feeling is associated with longer response latencies than recognition-by-knowing, and increases when subjects are given a long time to think about their responses. False recognition is often accompanied by “feeling,” but rarely accompanied by “knowing,” so that signal-detection measures of recognition accuracy are higher for knowing than for feeling. Recognition-by-knowing increases with additional study trials, eventually supplanting recognition-by-remembering, while recognition-by-feeling drops essentially to zero. In these and other ways, knowing the past can be distinguished from the feeling of familiarity.

While these experimental findings support a tripartite classification of recollective experience into remembering, knowing, and feeling, there is also “believing” – the inference that an event occurred, in the absence of any recollection at all. Remembering-as-believing is relevant to the controversy over recovered memories and “false memory syndrome,” if patients have been inappropriately persuaded by their therapists, friends, or prevailing cultural memes that they were traumatized in the past (Kihlstrom Reference Kihlstrom, Lynn and McConkey1998; Reference Kihlstrom, Uttl, Ohta and Siegenthaler2006; McNally Reference McNally2003). It may also be involved in cases of false confession (Kassin Reference Kassin2008; Reference Kassin2017). “Believing” may also be involved in memory illusions observed under laboratory conditions (Roediger Reference Roediger1996), including the post-event misinformation effect (Loftus Reference Loftus2005; Loftus & Palmer Reference Loftus and Palmer1974) and the associative and categorical memory illusions (Gallo Reference Gallo2010; Knott et al. Reference Knott, Dewhurst and Howe2012; Roediger & McDermott Reference Roediger and McDermott1995; Smith et al. Reference Smith, Ward, Tindell, Sifonis and Wilkenfeld2000). Having studied a list of vehicles, for example, subjects may be inclined to incorrectly say “Yes” to items on a recognition test only because they, too, name types of vehicles. This might be an associative priming effect, similar to familiarity, but it might also simply reflect the subject's beliefs about the items that were on the list.

Just as there is more to memory than recollection and familiarity, there is more to memory than the medial temporal lobe (MTL). Long ago, Bartlett (Reference Bartlett1932) argued that remembering went far beyond mere trace retrieval, and involved problem-solving, inference, and even creativity as the individual reconstructed a mental representation of the past. More recently, Mandler (Reference Mandler1980) reminded us that recognition involved the judgment of prior occurrence, suggesting that signal-detection analyses should pay as much attention to the bias in the decision process as we do to the sensitivity of the sensory process. The implication is that, in examining the neural substrates of recollection, familiarity, and other memory retrieval processes, we need to move beyond our almost-exclusive focus on the MTL, as Bastin et al. and others (e.g., Ranganath & Ritchey Reference Ranganath and Ritchey2012) have begun to do. Considering recollective experiences such as knowing, feeling, and believing may take our understanding of memory retrieval beyond recollection and familiarity, and expand our understanding of the neural bases of memory even further.