Exploring the semantic representational space: Behavioural and neural bases of social semantics

Abstract

Social experience, or socialness, is an essential aspect of human life that promotes learning and survival. This is also pervasive in language and can represent an interplay between social cognition, the processes involved in sustaining interactions with others, and semantic cognition, which is responsible for ascribing meaning to everything that surrounds us. While evidence shows that social knowledge might be one type of semantic knowledge, more is left to be understood about what represents social semantic knowledge. Recent work has focused on quantifying the social content of words by capturing diverse aspects of social experience, which also demonstrated that socialness was a unique aspect of meaning at behavioural level. Given the broadness of this dimension, it is important to understand to what extent it is unique or capturing other aspects of meaning at behavioural and neural level, which will be the focus of this thesis.
Moreover, the study of semantic knowledge has been limited by the omission of one important aspect of human behaviour, namely reward. According to neuropsychological theories, reward is composed of an affective experiential aspect (i.e., pleasure or receipt of reward) and an evaluative aspect (i.e., motivation or anticipation of reward). The former has been often used to equate reward, and it has been extensively studied in the semantics literature as emotional valence. However, this provides an incomplete picture, as the motivation aspect has not been addressed. Thus, another aim of this thesis was to conceptualise a measure of motivation for the first time. This thesis will focus on combining these two streams of literature to expand our understanding of semantic representations and particularly socialness.
Chapter 2 conceptualizes the evaluative aspect of hedonic experience in semantics for the first time, by defining a dimension called “motivation” and collecting a large set of word ratings for over 8,000 individual concepts. These norms are then used to assess the relationship between motivation and i) established semantic dimensions; and ii) behavioural performance on a set of lexical, semantic, and recognition memory tasks using mega-study data. The results demonstrate that motivation is a unique and behaviourally-relevant aspect of conceptual representation.
Chapter 3 examines i) the behavioural and neural bases of socialness using a new and broad definition and ii) the relationship between socialness and motivation in an online behavioural experiment and an fMRI experiment. The results show that social concepts, as re-defined, were associated with more accurate responses and engaged the anterior middle temporal gyrus, while the ventrolateral anterior temporal lobe showed a category-general response, consistent with previous research. Additionally, the neural patterns of activation associated with socialness and motivation were decoded above chance in the left temporal pole and anterior middle temporal gyrus, while each dimension was decoded across levels of association with the other in the anterior middle temporal gyrus, suggesting independence. This demonstrates that the two dimensions make distinct contributions to semantic representation.
This thesis provides novel insights into the organisation of the semantic representational space, emphasising the role of multiple sources of information in forming semantic representations.

Date of Award	5 Mar 2026
Original language	English
Supervisor	Manon Jones (Supervisor) & Richard Binney (Supervisor)