Accurate forced-choice recognition without awareness of memory retrieval

Abstract

Recognition confidence and the explicit awareness of memory retrieval commonly accompany accurate responding in recognition tests. Memory performance in recognition tests is widely assumed to measure explicit memory, but the generality of this assumption is questionable. Indeed, whether recognition in nonhumans is always supported by explicit memory is highly controversial. Here we identified circumstances wherein highly accurate recognition was unaccompanied by hallmark features of explicit memory. When memory for kaleidoscopes was tested using a two-alternative forced-choice recognition test with similar foils, recognition was enhanced by an attentional manipulation at encoding known to degrade explicit memory. Moreover, explicit recognition was most accurate when the awareness of retrieval was absent. These dissociations between accuracy and phenomenological features of explicit memory are consistent with the notion that correct responding resulted from experience-dependent enhancements of perceptual fluency with specific stimuli-the putative mechanism for perceptual priming effects in implicit memory tests. This mechanism may contribute to recognition performance in a variety of frequently-employed testing circumstances. Our results thus argue for a novel view of recognition, in that analyses of its neurocognitive foundations must take into account the potential for both (1) recognition mechanisms allied with implicit memory and (2) recognition mechanisms allied with explicit memory.An important principle in memory research is that there are characteristic behavioral, cognitive, subjective, and neural features that set explicit memory apart from other expressions of memory (Gabrieli 1998;Squire 2004;Paller et al. 2008). Explicit memory tests are those wherein direct reference is made to prior learning events, such as when subjects deliberately discriminate repeat from novel items in a recognition test. Memory measured by such tests is referred to as explicit memory. Hallmark features of explicit memory include the awareness of memory retrieval and confidence in memory judgments. Explicit memory can be contrasted with another form of memory, implicit memory, which does not require the realization that memory has influenced behavior. Specialized tests in which no reference is made to prior learning episodes are commonly used to measure implicit memory. Tests of perceptual priming, for example, are used to measure implicit memory for physical stimulus features, and perceptual priming with visual stimuli is thought to be supported by repetition-induced enhancements in neural processing fluency within visual cortex (Wiggs and Martin 1998;Schacter et al. 2007).A central emphasis of contemporary memory research has been to determine how explicit memory and implicit memory are related. Many researchers have proposed that recognition may derive partly from repetition-based perceptual fluency, the same mechanism that mediates perceptual priming (e.g., Jacoby and Dallas 1981;Johnston et al. 1991;Verfaellie and Cermak 1...

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“…With regard to the studies of Voss and colleagues (Voss et al, 2008;Voss & Paller, 2009, we agree with those authors that the term "implicit memory" should be reserved for cases in which individuals' performance shows evidence of memory for previous events, yet they are unaware that their responses are based on memory. By this definition, choices accompanied by feelings of either recollection or familiarity (or given with either "remember" or "know" responses) are classified as cases of explicit memory.…”

Real-Time Neural Signals of Perceptual Priming with Unfamiliar Geometric Shapes

“…In the other, we described negative old/new effects in conjunction with implicit perceptual fluency for repeated kaleidoscopes in a recognition test (Voss and Paller, 2009a). On the basis of several findings, we inferred that subjects taking a two-alternative forcedchoice recognition test could accurately discriminate old kaleidoscopes without being aware of the accuracy of their decisions -they guessed correctly without experiencing either familiarity or recollection, a phenomenon we termed "implicit recognition" (Voss et al, 2008;Voss and Paller, 2009a). When kaleidoscopes supported strong explicit recognition instead, old/new effects were quite distinct from those found here (Voss and Paller, 2009b).…”

“…Although explicit memory was not tested here, accuracy was very low in a yes-no recognition test with divided-attention study conditions similar to those used here (Voss et al, 2008), and inten- tional encoding with overt retrieval demands were only used in the prior design. Collectively, these considerations justify the interpretation that explicit retrieval was minimal in the current circumstances and that negative old/new effects were reflections of the processing responsible for implicit memory in the priming test.…”

“…Visual stimuli were 132 kaleidoscope images constructed using methods described in detail previously (Voss et al, 2008;Voss and Paller, 2009a). Each kaleidoscope image was constructed by deforming three, four, or five overlaid hexagons, with each hexagon having a unique, randomly selected color other than black ( Fig.…”

Recognition without awareness in humans and its implications for animal models of episodic memory

“…In our recent report, 10 we provide the first evidence that the fluency scenario is plausible by showing that recognition based only on visual fluency can occur in humans. Subjects in our experiments studied abstract kaleidoscope images that could not be easily named or associated with concepts.…”