Are associative memories forgotten more quickly than item memories, and does the level of original learning differentially influence forgetting rates? In this study, we addressed these questions by having participants learn single words and word pairs once (Experiment 1), three times (Experiment 2), and six times (Experiment 3) in a massed learning (ML) or a distributed learning (DL) mode. Then they were tested for item and associative recognition separately after four retention intervals: 10 min, 1 d, 1 wk, and 1 mo. The contribution of recollection and familiarity processes were assessed by participants' remember/know judgments. The results showed that for both item and associative memories, across different degrees of learning, recollection decreased significantly and was the main source of forgetting over time, whereas familiarity remained relatively stable over time. Learning multiple times led to slower forgetting at shorter intervals, depending on recollection and familiarity processes. Compared with massed learning, distributed learning (six times) especially benefited associative memory by increasing recollection, leading to slower forgetting at longer intervals. This study highlighted the importance of process contribution and learning experiences in modulating the forgetting rates of item and associative memories. We interpret these results within the framework of a dual factor representational model of forgetting (as noted in a previous study) in which recollection is more prone to decay over time than familiarity.According to the contents of the retrieved information, memory can be divided into item memory and associative memory (Murdock 1997; Squire and Wixed 2011). Unlike on tests of item memory, on tests of associative memory, participants have to determine whether the relations between items, or item-context relations, are learned during a study. Establishing and maintaining associations between items is an important aspect of episodic memory. Whether associative memory relies on different mechanisms from item memory remains a central issue of memory research (Murdock 1997;Squire et al. 2004;Davachi 2006). Many studies have suggested that they are dissociated in both behavioral mechanisms and neural substrates, with associative memory relying primarily on recollection and item memory, on familiarity (Gardiner et al. 2002;Cohn and Moscovitch 2007;Eichenbaum et al. 2007). In addition, the hippocampus is critical for and more involved in associative memory than in item memory, whereas the opposite holds for the perirhinal cortex (Davachi 2006;Eichenbaum et al. 2007; but see ). Recent evidence, however, suggests that item and associative memory can both depend on recollection and familiarity (Smith et al. 2011), and it is these processes, rather than the types of memory, that determine the neural substrates that are implicated. Less is known, however, about the factors that determine the rate of forgetting for items and associations (e.g., Wixted 1990;Hockley and Consoli 1999;Sadeh et al. 2014). In ...

Emotional stimuli can be processed even when participants perceive them without conscious awareness, but the extent to which unconsciously processed emotional stimuli influence implicit memory after short and long delays is not fully understood. We addressed this issue by measuring a subliminal affective priming effect in Experiment 1 and a long-term priming effect in Experiment 2. In Experiment 1, a flashed fearful or neutral face masked by a scrambled face was presented three times, then a target face (either fearful or neutral) was presented and participants were asked to make a fearful/neutral judgment. We found that, relative to a neutral prime face (neutral–fear face), a fearful prime face speeded up participants' reaction to a fearful target (fear–fear face), when they were not aware of the masked prime face. But this response pattern did not apply to the neutral target. In Experiment 2, participants were first presented with a masked faces six times during encoding. Three minutes later, they were asked to make a fearful/neutral judgment for the same face with congruent expression, the same face with incongruent expression or a new face. Participants showed a significant priming effect for the fearful faces but not for the neutral faces, regardless of their awareness of the masked faces during encoding. These results provided evidence that unconsciously processed stimuli could enhance emotional memory after both short and long delays. It indicates that emotion can enhance memory processing whether the stimuli are encoded consciously or unconsciously.

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