Semantic representation –the knowledge that we have of the world– is an essential component of our mind whose nature can be inferred from similarity measures, which we use every day to compare entities on the basis of their meaning.
Many research efforts have been made to understand our knowledge, however, 1) which information is used to represent meaning and 2) the way our brains organize semantic representations still remain hot topics of debate in the field.
The project aims to address these queries, by investigating, for the first time, the relation between semantic representations at three different levels: behaviour, models and brain activity.
We will use (1) a state-of-the-art technique (Representational Similarity Analysis) that has heralded a new research era in the study of semantics since it allows one-to-one mappings between patterns of brain-activity measurement, behavioural and computational models and (2) dimensionality-reduction approaches.
We know two main contrasting approaches to the study of meaning:
embodied theories propose similarity dimensions arisen by our sensory-motor experience;
distributional theories propose similarity dimensions derived by the distribution of words across spoken and written language.
Figure 1. Ilustration of experiential and distributional representations for 5 concepts (similarity matrices), showing conceptual similarity based on textual occurrence and overlap of featural descriptions.
Figure 2: Examples of different semantic representations (similarity matrices) based on behavioural, experiential, distributional, and combined models, as well as their representational similarity (lower right corner).
We know that embodied and distributional similarity dimensions are not totally independent but rather complementary.
Combined information of the two data sources would make it possible to capture similarity structures that define categories of meaning, such as the cluster of features that places “grape” and “marble” in different categories despite a superficial visual similarity, and “cherry” and “banana” in the same category despite very different appearances.