Priming of familiar and unfamiliar visual objects over delays in young and older adults.

Abstract

Although priming of familiar stimuli is usually age invariant, little is known about how aging affects priming of pre-experimentally unfamiliar stimuli. Therefore, this study investigated the effects of aging and encoding-to-test delays (0 min, 20 min, 90 min, and 1 week) on priming of unfamiliar objects in block-based priming paradigms. During the encoding phase, subjects viewed pictures of novel objects (Experiments 1 and 2) or novel and familiar objects (Experiment 3) and judged their left/right orientation. In the test block, priming was measured using the possible/impossible objectdecision test (Experiment 1), symmetric/asymmetric object-decision test (Experiment 2), and real/ non-real object-decision test (Experiment 3). In Experiments 1 and 2, young adults showed priming for unfamiliar objects at all delays, whereas older adults whose baseline task performance was similar to that of young adults did not show any priming. Experiment 3 found no effects of age or delay on priming of familiar objects; however, priming of unfamiliar objects was only observed in the young subjects. This suggests that when older adults cannot rely on pre-existing memory representations, age-related deficits in priming can emerge. KeywordsPerceptual priming; aging; unfamiliar visual objects; implicit memory; object decision test It is well known that normal aging is accompanied by a reduction in explicit memory, or the ability to consciously recall or recognize previously experienced information (Cabeza, Nyberg, & Park, 2005). In contrast, another type of memory, priming, remains relatively intact in healthy older adults (D. A. Fleischman, 2007;D.A. Fleischman & Gabrieli, 1998;Light, Prull, La Voie, & Healy, 2000). Priming is a type of implicit memory and refers to a change in performance (e.g., speed, accuracy, or bias) for a previously encountered stimulus compared to a new stimulus. Priming can occur in the absence of conscious memory for a stimulus and NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript is thought to rely on different neural structures than explicit memory (reviewed in Henson, 2003).Notably, one important theoretical question that has received very little attention in studies of priming is whether intact priming in older adults relies on the existence of pre-existing memory representations. Whereas priming for familiar stimuli is largely based on the reactivation of existing memory representations, priming for novel stimuli has been suggested to be mediated by newly acquired representations (Bowers, 1994(Bowers, , 1996Henson, Shallice, & Dolan, 2000;Schacter, Cooper, & Delaney, 1990). Of the over 100 studies investigating the effects of aging on priming, we are aware of only six studies that used pre-experimentally unfamiliar stimuli (Keane, Wong, & Verfaellie, 2004;Light, Kennison, Prull, LaVoie, & Zuellig, 1996;Light, La Voie, & Kennison, 1995;Schacter, Cooper, & Valdiserri, 1992;Soldan, Gazes, Hilton, & Stern, 2008;Wiggs & Martin, 1994) and all but two them Soldan, Gazes et a...

Understanding age-related reductions in visual working memory capacity: Examining the stages of change detection

“…Unlike the younger adults, older adults did not exhibit either the FN400 or the N300, suggesting that they did not experience fluency that could have informed their behavioral responses. Although older adults exhibit intact priming (Fleischman, 2007), they may rely on long-term semantic representations (e.g., everyday objects or easily labeled colors) for visual priming (Soldan, Hilton, Cooper, & Stern, 2009), which would not have been activated in the present study. As with the dual-process model, the fluency heuristic model would interpret the late-stage neural activity in older adults as a failure to activate a familiarity or recollection process, but as successful activation of postretrieval monitoring and verification processes.…”

Age effects on explicit and implicit memory

“…Several longitudinal studies have demonstrated stable priming with advancing age despite substantial declines in explicit memory (Hultsch et al, 1992; Christensen et al, 1997; Davis et al, 2001; Fleischman et al, 2004). Moreover, many cross-sectional studies employing a range of different tasks have reported non-significantly different priming between groups of young and older adults (e.g., Mitchell et al, 1990; Light et al, 1992; Park and Shaw, 1992; Schacter et al, 1992; Mitchell and Bruss, 2003; Wiggs et al, 2006; Soldan et al, 2009; Spaan and Raaijmakers, 2011). …”

Bias effects in the possible/impossible object decision test with matching objects

“…Thus, when the original non-matching possible and impossible stimuli developed by Schacter and Cooper were used with the same experimental design as that of Experiment 1, Soldan, Hilton et al (in press, Experiment 1) found the typical pattern of results: priming for possible objects and nil priming for impossible objects. Given that the only procedural difference between these two experiments was the addition of the matched objects during the test phase in Experiment 1 of this study, the negative priming effect for old impossible objects in Experiment 1 might be attributable to the fact that the matched objects reduced the putative influence of explicit memory on task performance, as postulated by Ratcliff and McKoon (1995) and Williams and Tarr (1997).…”

“…By comparison, the set of impossible objects (N = 152) from which Schacter and Cooper chose their stimuli consisted of approximately 13%, 28%, and 59% of stimuli with 1, 2, and 3+ structural violations. Likewise, Experiment 1 by Soldan, Hilton et al (in press), which used the original Schacter and Cooper stimuli with the same design as the present study, the proportion of impossible objects (N=48) with 1, 2, and 3 or more structural violations was 13%, 29%, and 58%, respectively. This change in the composition of the impossible stimuli was unavoidable because we desired a similar proportion of objects with 1, 2, or 3 structural violations in order to test the predictions of the structure-extraction bias model.…”

“…Such a change would be predicted according to the bias models if the matched objects indeed influence the degree to which subjects relied on explicit memory to perform the possible/impossible object-decision test. Notably, the same experimental design implemented in this study, including the delay manipulation, has been used in an experiment with the original non-matching possible and impossible objects developed by Schacter and Cooper and been shown to produce priming for possible but not impossible objects across all tested encoding-totest delays in young adults (Soldan, Hilton, Cooper, & Stern, in press)1. This means that any difference in the pattern of priming between the present results and those obtained in the study using the non-matching objects can only be attributed to the matched objects manipulation.…”