Language Comprehension in the Balance: The Robustness of the Action-Compatibility Effect (ACE)

Bouwmeester S (2012) Language Comprehension in the Balance: The Robustness of the Action-Compatibility Effect (ACE). PLoS ONE 7(2): e31204. doi:10.1371/journal.pone.0031204 Language Comprehension in the Balance: The Robustness of the Action-Compatibility Effect (ACE) Rolf A. Zwaan 0 Nathan van der Stoep 0 Tulio Guadalupe 0 Samantha Bouwmeester 0 Esteban Andres Fridman, Centre de Neuroscience Cognitive, France 0 1 Department of Psychology, Erasmus University Rotterdam , Rotterdam , The Netherlands , 2 Department of Experimental Psychology, Hemholtz Institute, Utrecht University, The Netherlands, 3 Max Planck Institute for Psycholinguistics , Nijmegen , The Netherlands How does language comprehension interact with motor activity? We investigated the conditions under which comprehending an action sentence affects people's balance. We performed two experiments to assess whether sentences describing forward or backward movement modulate the lateral movements made by subjects who made sensibility judgments about the sentences. In one experiment subjects were standing on a balance board and in the other they were seated on a balance board that was mounted on a chair. This allowed us to investigate whether the action compatibility effect (ACE) is robust and persists in the face of salient incompatibilities between sentence content and subject movement. Growth-curve analysis of the movement trajectories produced by the subjects in response to the sentences suggests that the ACE is indeed robust. Sentence content influenced movement trajectory despite salient inconsistencies between implied and actual movement. These results are interpreted in the context of the current discussion of embodied, or grounded, language comprehension and meaning representation. - What happens when we understand a sentence like The boy dove into the pool? The traditional assumption is that we construct a language-like mental representation, such as [[P1,DOVE, BOY] [P2, INTO, POOL, P1]], whereby the first proposition, P1, represents the fact that the boy dove and the second proposition, P2, that the target location of this action was the pool. This representation captures the intuition that the sentence conveys two things about the described situation. However, such representations may be viewed as a convenient shorthand of the mental representations actually formed by comprehenders [1]. According to more recent theories of cognition [24], mental representations can be summarized in language-like propositions for certain research purposes but they should be thought of as mental representations that are grounded in the brains systems for perception and action. For example, in the case of the example sentence the comprehender might form a visual representation of the pool, a somatosensory representation of cool water suddenly enveloping the body, and a motor representation of the act of diving. In this article, we are concerned with this latter component of a purported sensorimotor representation: the motor component. Language comprehension and the brains motor system interact. This has been demonstrated by numerous behavioral and neuroimaging studies, but the exact interpretation of these findings remains unclear. There is, for example discussion as to whether motor activation is necessary for comprehension or whether it is the result of other levels of processing [57]. To begin tackling this issue, it is useful to revisit what has proved the most influential behavioral evidence regarding the role of motor activation in language comprehension: the action-compatibility effect [8]. How robust is this effect? Does it occur even when the action to be performed by the subject is incompatible on a number of important dimensions with the action described in the text? In a seminal study [8], subjects made sensibility judgments to sentences (does the sentence make sense yes or no?) by releasing a button and pressing one of two buttons located either closer to the body or farther away from the body. On some critical trials, the sentence described an action that involved moving the hand toward or away from the body. For example, a sentence like He closed the drawer describes an action that involves moving the hand away from the body, whereas He opened the drawer describes an action that involves moving the hand toward the body. The key finding, which was dubbed the action-compatibility effect (ACE) [8], was that responses were faster when the action described in the sentence was congruent with the action the subject had to perform to respond to the sentence than when the action was incongruent. In further pursuit of this line of thinking, a later study introduced a related paradigm that allowed the researchers to examine the waxing and waning of motor resonance during sentence comprehension (rather than at the end of the sentence) [9]. In this paradigm, subjects read sentences incrementally a few words at a time by rotating a knob, with five degrees of rotation corresponding to the presentation of a new sentence segment. The critical sentences in their experiments all involved manual rotation (e.g., opening a bottle, screwing in a light bulb). The main finding was that ACE occurred during sentence processing and more specifically that its occurrence coincided with linguistic focus on the action [10]. What these ACE studies have in common is that the action performed by the subject is very similar to the actions described in the sentences. For example, turning a knob is similar to opening a bottle. From the standpoint of trying to find constraints on motor activation in language processing, however, it is important to know whether ACE effects are eliminated when the action performed by the subjects is incongruent or even inconsistent with the described action. But how can an ACE be examined if the described action and the performed action are incompatible? The answer resides in the fact that compatibility is not an all-or-none phenomenon. Actions can be decomposed into different components. Take the action described by He dove into the pool. This action might have components such as bending the knees, pushing off, putting the arms forward, and putting the head between the arms. This action is clearly incompatible with standing straight up and moving the body slightly to the right, as this is orthogonal to the described direction. However, if the ACE is robust and not task specific, one might still expect a small forward component in this transversal movement. Conversely, one might expect a small backward component if the sentence describes a backward movement, as in The teenager plopped down on the couch. An even stronger incompatibility between described and performed action arises when the starting postures are different. For example, diving normally presupposes that one is standing. So if subjects are seated and moving their body sideways to respond to the sentences, there is a postural and a direct (...truncated)