concepts play a central role in human behaviour and constitute a critical component of the human conceptual system. Here, we investigate the neural basis of four types of abstract concepts, examining their similarities and differences through neuroimaging meta-analyses. We examine numerical and emotional concepts, and two higher-order abstract processes, morality judgements and theory of mind. Three main findings emerge. First, representation of abstract concepts is more widespread than is often assumed. Second, representations of different types of abstract concepts differ in important respects. Each of the domains examined here was associated with some unique areas. Third, some areas were commonly activated across domains and included inferior parietal, posterior cingulate and medial prefrontal cortex. We interpret these regions in terms of their role in episodic recall, event representation and social-emotional processing. We suggest that different types of abstract concepts can be represented and grounded through differing contributions from event-based, interoceptive, introspective and sensory-motor representations. The results underscore the richness and diversity of abstract concepts, argue against single-mechanism accounts for representation of all types of abstract concepts and suggest mechanisms for their direct and indirect grounding.This article is part of the theme issue 'Varieties of abstract concepts: development, use and representation in the brain'.

Embodied theories of language processing suggest that this motor simulation is an automatic and necessary component of meaning representation. If this is the case, then language and action systems should be mutually dependent (i.e., motor activity should selectively modulate processing of words with an action-semantic component). In this paper, we investigate in two experiments whether evidence for mutual dependence can be found using a motor priming paradigm. Specifically, participants performed either an intentional or a passive motor task while processing words denoting manipulable and nonmanipulable objects. The performance rates (Experiment 1) and response latencies (Experiment 2) in a lexical-decision task reveal that participants performing an intentional action were positively affected in the processing of words denoting manipulable objects as compared to nonmanipulable objects. This was not the case if participants performed a secondary passive motor action (Experiment 1) or did not perform a secondary motor task (Experiment 2). The results go beyond previous research showing that language processes involve motor systems to demonstrate that the execution of motor actions has a selective effect on the semantic processing of words. We suggest that intentional actions activate specific parts of the neural motor system, which are also engaged for lexical-semantic processing of action-related words and discuss the beneficial versus inhibitory nature of this relationship. The results provide new insights into the embodiment of language and the bidirectionality of effects between language and action processing.

The role of the two hemispheres in processing metaphoric language is controversial. While some studies have reported a special role of the right hemisphere (RH) in processing metaphors, others indicate no difference in laterality relative to literal language. Some studies have found a role of the RH for novel/unfamiliar metaphors, but not conventional/familiar metaphors. It is not clear, however, whether the role of the RH is specific to metaphor novelty, or whether it reflects processing, reinterpretation or reanalysis of novel/unfamiliar language in general. Here we used functional magnetic resonance imaging (fMRI) to examine the effects of familiarity in both metaphoric and non-metaphoric sentences. A left lateralized network containing the middle and inferior frontal gyri, posterior temporal regions in the left hemisphere (LH), and inferior frontal regions in the RH, was engaged across both metaphoric and non-metaphoric sentences; engagement of this network decreased as familiarity decreased. No region was engaged selectively for greater metaphoric unfamiliarity. An analysis of laterality, however, showed that the contribution of the RH relative to that of LH does increase in a metaphor-specific manner as familiarity decreases. These results show that RH regions, taken by themselves, including commonly reported regions such as the right inferior frontal gyrus (IFG), are responsive to increased cognitive demands of processing unfamiliar stimuli, rather than being metaphor-selective. The division of labor between the two hemispheres, however, does shift towards the right for metaphoric processing. The shift results not because the RH contributes more to metaphoric processing. Rather, relative to its contribution for processing literals, the LH contributes less.

The acquisition of bidirectional action–effect associations plays a central role in the ability to intentionally control actions. Humans learn about actions not only through active experience, but also through observing the actions of others. In Experiment 1, we examined whether action–effect associations can be acquired by observational learning. To this end, participants observed how a model repeatedly pressed two buttons during an observation phase. Each of the buttonpresses led to a specific tone (action effect). In a subsequent test phase, the tones served as target stimuli to which the participants had to respond with buttonpresses. Reaction times were shorter if the stimulus–response mapping in the test phase was compatible with the action–effect association in the observation phase. Experiment 2 excluded the possibility that the impact of perceived action effects on own actions was driven merely by an association of spatial features with the particular tones. Furthermore, we demonstrated that the presence of an agent is necessary to acquire novel action–effect associations through observation. Altogether, the study provides evidence for the claim that bidirectional action–effect associations can be acquired by observational learning. Our findings are discussed in the context of the idea that the acquisition of action–effect associations through observation is an important cognitive mechanism subserving the human ability for social learning.

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