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

Abstract

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.

No evidence of fast mapping in healthy adults using an implicit memory measure: Failures to replicate the lexical competition results of Coutanche and Thompson‐Schill (2014)

“…Nonetheless, in a post-hoc analysis, where we split trials according to whether the hermit word was natural versus man-made (which was the dimension probed in the speeded semantic decision task used to assess implicit memory), we did find significant priming effects: RTs for natural hermit words (after FM learning) were speeded when those words had a studied neighbour relative to when they did not, whereas RTs for man-made hermit words were slowed when those words had a studied neighbour relative to when they did not. This pattern is more consistent with a semantic priming effect than a lexical competition effect, and similar to the semantic priming effect reported by Zaiser et al (2021).…”

“…One possibility is that the presence of a referent object and mention of a semantic feature in the yes/no question in the FM condition (but not EE condition) increased the number of items activated that are from the natural category, e.g., if the hermit word, its studied neighbour and its studied referent were all brought to mind by spreading activation. If so, the effect should be reduced if the referent is removed from the FM condition (similar to Zaiser et al, 2021). We addressed this possibility in Experiment 2.…”

“…We also took the opportunity to add a third learning condition (i.e., test a third group of participants, see Figure 1). This was the "FM-r" variant of FM learning that we previously used in Cooper et al (2019b) to test whether the presence or absence of the object referent is necessary to obtain a FM effect in explicit memory that is distinct from EE learning (and similar to the variants used by Coutanche &Thompson-Schill, 2014, andZaiser et al, 2021). Previous studies of fast mapping suggested that a known referent is important (Sharon et al 2011), e.g., in helping support integration of the new information into existing semantic knowledge (Coutanche & Thompson-Schill, 2015).…”

“…(The 3AFC test where the studied neighbours are presented with only animal pictures as choices might re-inforce this semantic link.) This would be a form of semantic priming, possibly related to that reported by Zaiser et al (2021). With this in mind, we re-examined the data, splitting hermit words according to whether they were semantically congruent with the study category (of natural animals).…”

“…After completion of the present experiments, including our pre-registered Experiment 2, another study (Zaiser, Meyer & Bader, 2021) reported a partial replication of the lexical competition effect of Coutanche and Thompson-Schill (2014). In Experiment 1 of their study, Zaiser and colleagues report lexical competition (i.e., slowing for hermit words with neighbours) four minutes after FM encoding, when combining their "high" and "low" feature overlap conditions (which refer to the degree of feature overlap between known and unknown items).…”