The missing link? Testing a schema account of unitization

Abstract

Unitization refers to the creation of a new unit from previously distinct items. The concept of unitization has been used to explain how novel pairings between items can be remembered without requiring recollection, by virtue of new, item-like representations that enable familiarity-based retrieval. We tested an alternative account of unitization - a schema account - which suggests that associations between items can be rapidly assimilated into a schema. We used a common operationalization of "unitization" as the difference between two unrelated words being linked by a definition, relative to two words being linked by a sentence, during an initial study phase. During the following relearning phase, a studied word was re-paired with a new word, either related or unrelated to the original associate from study. In a final test phase, memory for the relearned associations was tested. We hypothesized that, if unitized representations act like schemas, then we would observe some generalization to related words, such that memory would be better in the definition than sentence condition for related words, but not for unrelated words. Contrary to the schema hypothesis, evidence favored the null hypothesis of no difference between definition and sentence conditions for related words (Experiment 1), even when each cue was associated with multiple associates, indicating that the associations can be generalized (Experiment 2), or when the schematic information was explicitly re-activated during Relearning (Experiment 3). These results suggest that unitized associations do not generalize to accommodate new information, and therefore provide evidence against the schema account.

Keywords: Familiarity; Recognition; Recollection; Schema; Unitization.

Figure 1

Schematic depiction of unitization encoding (top) and generalization (bottom) under an item account (left) and a schema account (right). Blue colouring indicates items and links that already exist in the network (we use the term “existing links” to refer to items that similarly fit with the definition). Red colouring indicates new links and items that are learned during encoding or generalization. Solid lines indicate components that are explicitly activated during encoding or generalization, while dashed lines indicate components in the network that are not explicitly presented but can be activated indirectly (e.g., via pre-existing links). Interrupted red lines (item account) represent temporary links, which only remain active until the “fused” representation is created. Green cloud (schema account) represents a schema that can bind items together.

Figure 2

Illustration of the experimental design of Experiment 1. Definition and sentence blocks only differed at study phase. The test trial in the example corresponds to the related trial in the relearning phase. The target response (MOON) is highlighted. Other response types are old-different (TEA), new-related (STAR), and new-unrelated (LEMONADE). Repetition of word pairs in the figure is for illustrative purposes: during the task, each word-pair was only presented once under definition / sentence encoding and once under repeat / related / unrelated relearning.

Figure 3

Experiment 1: Proportion of correct responses at test, in the various encoding and relearning conditions. The two leftmost bars represent accuracy in the repeat (control) condition. Performance for repeated trials was significantly better for the definition than sentence conditions, consistent with the basic unitisation effect (***p < .005). The four bars on the right represent accuracy in the related and unrelated conditions. The predicted interaction between study condition and relearning condition was not significant (n.s). Error bars represent SEs for each condition separately.

Figure 4

Experiment 2: Proportion of correct responses at test, in the various encoding and relearning conditions. Bars represent accuracy in the related and unrelated conditions. The predicted interaction between study condition and relearning condition was not significant (n.s.). Error bars represent SEs for each condition separately.

Figure 5

Experiment 3: Proportion of correct responses at test, in the various encoding and relearning conditions. The two leftmost bars represent accuracy in the repeat (control) condition. Performance for repeated trials was significantly better for the definition than sentence conditions, consistent with the basic unitisation effect. The four bars on the right represent accuracy in the related and unrelated conditions (***p < .005). The predicted interaction between study condition and relearning condition was not significant (n.s). Error bars represent SEs for each condition separately.

Figure 6

Forest plot showing study-specific estimates of the mean difference for Experiment 1-3 (squares) and the pooled mean difference (diamond). On the x-axis, positive numbers indicate that an outcome favours the related condition (i.e., greater difference between definition and sentence encoding for related than for unrelated relearning), as predicted by the schema hypothesis, while negative numbers indicate an outcome that favours the unrelated condition. In the current case, the outcome was approximately 0, supporting the null hypothesis.