High feature overlap and incidental encoding drive rapid semantic integration in the fast mapping paradigm.

Contrary to traditional theories, it has been shown that novel, arbitrary associations can be rapidly integrated into cortical networks through a learning paradigm called fast mapping (FM), possibly bypassing time-consuming hippocampal-neocortical consolidation processes. In the FM paradigm, an unknown item is presented next to a known item and participants answer a question referring to an unfamiliar label, presumably inferring that the label belongs to the unknown item. However, factors driving rapid cortical integration through FM are still under debate. The FM task requires the discrimination between complex objects and the binding of the unknown item to the label. Discriminating between complex and especially highly similar objects is a central function of the perirhinal cortex, a structure also involved in the binding of single elements to a unit. We suggested that triggering perirhinal processing by increasing the demands on item discrimination through increasing feature overlap between the unknown and the known item might foster the binding of the unknown item to the label and their rapid cortical integration. We found lexical integration of the labels after learning through FM, but this was not affected by feature overlap. However, semantic integration of the label immediately after FM encoding was more successful when the items shared many features than when they shared few features. Moreover, effects of rapid semantic integration through FM were reduced if encoding was intentional and if no discrimination was required. This indicates that incidental encoding and a high feature overlap are driving factors for rapid semantic integration through FM. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

High feature overlap reveals the importance of anterior and medial temporal lobe structures for learning by means of fast mapping.

Contrary to traditional theories of declarative memory, it has recently been shown that novel, arbitrary associations can rapidly and directly be integrated into cortical memory networks by means of a learning procedure called fast mapping (FM), possibly bypassing time-consuming hippocampal-neocortical consolidation processes. In the typical FM paradigm, a picture of a previously unknown item is presented next to a picture of a previously known item and participants answer a question referring to an unfamiliar label, thereby incidentally creating associations between the unknown item and the label. However, contradictory findings have been reported and factors moderating rapid cortical integration through FM yet need to be identified. Previous behavioral results showed that rapid semantic integration through FM was boosted if the unknown and the known item shared many features. In light of this, we propose that the perirhinal cortex might be especially qualified to support the rapid incorporation of these associations into cortical memory networks within the FM paradigm, due to its computational mechanisms during the processing of complex and particularly highly similar objects. We therefore expected that a high degree of feature overlap between the unknown and the known item would trigger strong engagement of the perirhinal cortex at encoding, which in turn might enhance rapid cortical integration of the novel picture-label associations. Within an fMRI experiment, we observed greater subsequent memory effects (i.e., stronger activation for subsequent hits than misses) during encoding in the perirhinal cortex and an associated anterior temporal network if the items shared many features than if they shared few features. This indicates that the perirhinal cortex indeed contributes to the acquisition of novel associations by means of FM if feature overlap is high.

Evidence for fast mapping in adults - Moderating factors yet need to be identified.

Cooper, Greve, and Henson (this issue) discuss if fast mapping (FM) is dissociable from other learning procedures in adults. We strongly agree that drawing conclusions on cortical integration from recognition accuracy is questionable in healthy young adults. Additionally, we advise against interpreting explicit measures in patient studies if residual hippocampal functioning cannot be excluded or extra-hippocampal structures are also affected. Due to promising fMRI data patterns and confounds in studies reporting no evidence for implicitly measured semantic integration, we suggest that factors moderating FM learning success need to be systematically identified rather than doubting rapid cortical integration through FM.

Homogeneity of item material boosts the list length effect in recognition memory: A global matching perspective.

Kinnell and Dennis (2012) showed that the list length effect in recognition memory is only observed for homogeneous stimulus material. On the basis of the global matching model MINERVA 2 (Hintzman, 1986, 1988), we offer a theoretical explanation for this finding. According to our analysis, homogeneous material immunizes against the disruptive influence of preexperimental items, which might mask the intralist interference predicted by global matching models for familiar heterogeneous material. We tested our approach in three experiments. In Experiment 1, we found list length effects for homogeneous photographs of flowers and landscapes. In Experiment 2 and 3, we presented heterogeneous photographs of scenes (Experiment 2) and faces (Experiment 3). List length effects were only found if these photographs were homogenized by the use of image-processing filters. We further show that our explanation is also in line with the results of Dennis and Chapman (2010) who found an inverse list length effect. Overall, our results provide evidence for a global matching account of familiarity. (PsycINFO Database Record (c) 2019 APA, all rights reserved).