Embodied language processing


occurs when an organism's sensorimotor capacities, body and environment play an important role in thinking. The way in which a person's body and their surroundings interacts also allows for specific brain functions to develop and in the future to be able to act. This means that not only does the mind influence the body's movements, but the body also influences the abilities of the mind, also termed the bi-directional hypothesis.
There are three generalizations that are assumed to be true relating to embodied cognition. A person's motor system is activated when they observe manipulable objects, process action verbs, and observe another individual's movements.
Embodied semantics is one of two theories concerning the location and processing of sensory motors inputs within the human brain. The theory of embodied semantics involves the existence of specialized hubs where the meaning of a word is tied with the sensory motor processing unit associated with the word meaning. For example, the concept of kicking would be represented in the sensory motor areas that control kicking actions. As a result, the theory assumes that individuals must possess a body to understand English.

Neural circuitry

The overlap between various semantic categories with sensory motor areas suggests that a common mechanism is used by neurons to process action, perception, and semantics. The correlation principle states that neurons that fire together, wire together. Also, neurons out of sync, delink. When an individual pronounces a word, the activation pattern for articulatory motor systems of the speaker leads to activation of auditory and somatosensory systems due to self-perceived sounds and movements.
If a word meaning is grounded in the visual shapes of the objects, the word form circuit is active together with neural activity in the ventral-temporal visual stream related to processing of visual object information. Correlation learning links the word and object circuits, resulting in an embodied object-semantic relationship. To study the embodiment effect on semantic processing of common adjectives and abstract nouns, people who were contrasted by their endurance, tempo, plasticity, emotionality, sex or age were tested using Semantic Projective Method. In these studies, males with stronger motor-physical endurance estimated abstractions describing people-, work/reality- and time-related concepts in more positive terms than males with weaker endurance. Females with stronger social or physical endurance estimated social attractors in more positive terms than weaker females. Both male and female temperament groups with higher sociability showed a universal positive bias in their estimations of social concepts, in comparison to participants with lower sociability.

Semantic hubs

A semantic hub represents a focal point in the brain where all semantic information pertaining to a specific word is integrated. For example, the color, shape, size, smell, and sound associated with the word "cat" would be integrated at the same semantic hub. Some candidate regions for semantic hubs include:
  1. Inferior Frontal Cortex: the anterior part of Broca's area and adjacent tissue in the left Inferior Frontal Cortex including Brodmann's areas 44, 45, and 47 are activated for semantic processing and functional changes.
  2. Superior Temporal Cortex: contains Wernicke's area which controls the classic posterior language area in and adjacent to the superior temporal gyrus and sulcus. This area is thought to be a semantic processor on the basis of lesion, perfusion, and imaging data.
  3. Inferior Parietal Cortex: angular and adjacent to supramarginal gyrus in inferior parietal cortex is thought to be most strongly activated during semantic processing of cross-modal spatial and temporal configurations.
  4. Inferior and middle temporal cortex: a general semantic binding site between words and their meaning in left or bilateral medial/inferior temporal cortex.
  5. Anterior temporal cortex: thought to be involved in semantic dementia. which is a severe and specific semantic deficit characterized by lesions to both temporal poles.
Semantic integration mechanisms involve various hub sites listed above, which contradicts the idea that there is one center where all integration occurs. However, each individual hub is compliant with the amodal model. Collectively, all of the hubs provide evidence for the theory that there are areas within the brain where emotional, sensory, and motor information all converge in one area.

Semantic category specificity

Each potential semantic hub is activated to a specific degree according to the category that the perceived word belongs to. For example, lesions to each of the five potential hubs do not affect all words. Instead, experimental data determines that one semantic category suffers more than another as it pertains to the word.
  1. Left Inferior Frontal Cortex and bilateral frontocentral motor systems: these two areas are strongly activated in response to action related words or phrases. Lesions to these two areas produces impairments in the processing of action related words and action related concepts.
  2. Bilateral superior temporal Cortex: this area is strongly activated in response to words related to sounds. Lesions to this area produce impairment in sound word processing.
  3. Left Inferior Parietal Cortex: especially near the supramarginal gyrus, this area is activated by spatial language. Lesions to the Inferior Parietal Cortex produced impairment involving spatial language such as prepositions.
  4. Medial/Inferior Temporal Cortex: this area is strongly activated by category-specific words animals, tools, person's names, color, and form. Lesions show impairment in category-specific words for these categories as well.
  5. Anterior Temporal Cortex: this area is associated with processing the differences between semantic categories.
Some of the category differences are thought to be produced by the adjacent hubs. For example, category specificity is greatest close to the piriform and anterior insular olfactory cortex. Here, odor words such as "cinnamon" lead to greater activation than control words. In the gustatory cortex in the anterior insula and frontal operculum, taste words such as "sugar" lead to a stronger activation.

Experiential trace hypothesis

Experiential Trace Hypothesis states that each time an individual interacts with the world, traces of that particular experience are left in our brain. These traces can be accessed again when a person thinks of words or sentences that remind them of that experience. Additionally, these traces in our brain are linked to the action that they are related to.
Words and sentences become those cues that retrieve these traces from our mind. Researchers have studied if the previous experience with a word, such as its location in space, affects how people understand and then respond to that word. In one experiment, researchers hypothesized that if reading an object word also activates a location that is linked to that noun, then the following action response should be compatible with that association. They found that participants were faster to push a button higher than another button when the word was associated with being "up" or "above" than when the button was lower than the other for words associated with "up" and "above".
The results of this study displayed that participants were faster to respond when the location of the word and the action they had to perform were similar. This demonstrates that language processing and action are connected. This research also found that the location information of a word is automatically activated after seeing the word. In a similar study, it was discovered that participants were equally as fast at responding to words that were associated with either an upward or downward location when the buttons to respond to these words were horizontal – meaning that the experiential trace effect was ruled out when the responding action did not link to either of the locations that were activated.

Experiential-simulation theory of language understanding

Some theorists have proposed an experiential-simulation approach of language understanding. They argue that previous experiential traces related to a word may be reactivated at a later stage when accessing the meaning of the same word. This has been highlighted through the example of encountering the word 'airplane' in a situation where someone points to an airplane in the sky, thus making one look upwards. These experiential traces, e.g. 'looking upwards' are later reactivated when accessing the meaning of the word 'airplane'. Similarly, another example might be when a person accesses the meaning of the word 'snail', they might also access experiential traces associated with this word, e.g. 'looking downwards'.

Language comprehension and motor systems involved in action

Concrete verbs

As a result of previous experience to certain words, several studies have found that the action associated with a certain word is also activated in the motor cortices when processing that same word. For example, using event-related functional magnetic resonance imaging, it was discovered that exposure to concrete action verbs referring to face, arm, or leg actions activated motor regions that are stimulated when making actions with the foot, hand, or mouth.

Abstract verbs

However, findings are not as clear cut when abstract verbs are involved. Embodied theories of language comprehension assume that abstract concepts, as well as concrete ones, are grounded in the sensorimotor system Some studies have investigated the activation of motor cortices using abstract and also concrete verbs, examining the stimulation of the motor cortices when comprehending literal action verbs vs. the metaphorical usage of the same action verbs. One such study used fMRI to study participants whilst they viewed actions performed by the mouth, hand or foot, and read literal and metaphorical sentences related to the mouth hand or foot. This study found activation in the premotor cortex for literal action but not for metaphorical usage. These findings suggest that the assumption of embodied theories that abstract concepts, as well as concrete ones, are grounded in the sensorimotor system may not be true.
However, in contrast, other research has found motor cortex activation for the metaphorical usage of action verbs. One such study investigated cortical activation during comprehension of literal and idiomatic sentences using Magnetoencephalography. During a silent reading task, participants were presented with stimuli which included both literal and metaphorical arm-related action verbs, e.g. "Mary caught the fish" versus "Mary caught the sun", and also literal and metaphorical leg-related action verbs, e.g. "Pablo jumped on the armchair" versus "Pablo jumped on the bandwagon". This study found that processing of abstract verbs did indeed activate motor regions of the brain, activating anterior fronto-temporal activity very early compared to literal verbs.