Relevance of the listener's motor system in recalling phrases enacted by the speaker

Explicit and implicit memory for the QWERTY keyboard: the role of motor simulation and deictic gestures

In three experiments, we investigated explicit and implicit knowledge about the location of letters on the QWERTY keyboard in young students, and the mechanisms involved. Participants completed a verbal report task in which they were asked to locate the 21 letters of the Italian alphabet on a blank QWERTY keyboard (explicit memory). Subsequently, they carried out a motor production task, i.e., typing letters on a blank keyboard (implicit memory). Consistent with previous studies and several theories emphasizing the importance of implicit knowledge in typing, results showed that explicit knowledge about the QWERTY keyboard is systematically worse than procedural knowledge (Experiment 1). These two types of knowledge, however, are related. Second, we showed that explicit memory for letter position was affected when participants were engaged in a secondary task that required hands/arms movements. Specifically, loading participants' sensorimotor resources led to a decrease in explicit memory performance when the secondary task required hand/arm movements (hand/arms tapping) compared to when it required legs-feet movements (control condition). This result suggests that explicit knowledge is modulated by sensorimotor simulation (Experiment 2). Third, compared to a purely verbal response, pointing to the key on the keyboard did not improve explicit memory accuracy (Experiment 3). Taken together, the results indicate that sensorimotor simulation, and not just gestures, modulates the accessibility to explicit mental representations of verbal/spatial material, like letters on a keyboard.

Action and posture influence the retrieval of memory for objects

The embodied approach states that memory traces are retrieved, at least in part, through a sensorimotor simulation of the original events, i.e., during retrieval we use our body and its sensorimotor pathways to simulate what happened during encoding. Thus, body manipulations that are incongruent with the motor elements involved at encoding should modulate memory performance. To test this hypothesis, we devised two experiments. In Experiment 1, participants had to observe (observation task) or observe and also perform an action on (enactment task) a series of objects. At recognition, they recognised the enacted objects faster and more accurately than the observed ones. Crucially, in Experiment 2, we manipulated body posture during recognition: one group was asked to hold their hands/arms in front of them (non-interfering group), and the other group was asked to block their hands/arms behind their back (interfering group). The results on reaction times, but not those on accuracy, showed a critical interaction: while the noninterfering group recognised enacted objects faster than observed objects, this advantage disappeared for the interfering group. This suggests that adopting a posture inconsistent with action at encoding could influence the time needed to correctly recognise the objects, but not the accuracy of the recognition.

The social cognitive dimension of pantomime

Pantomime production is commonly interpreted as reflecting tool-use-related cognitive processes. Yet, in everyday life, pantomime deserves a communication function and the exaggeration of amplitude found during pantomime compared to real tool use may reflect the individual's attempt to communicate the intended gesture. Therefore, the question arises about whether pantomime is a communicative behavior that is nevertheless supported only by non-social cognitive processes. We contribute to answering this question by using kinematic analyses. Participants performed the pantomime of using a saw or a hammer from visual presentation in three conditions: Free (no specific instructions), Self (focus on the real tool-use action), and Others (focus on the communicative dimension). Finally, they used the tool with the corresponding object (Actual condition). Participants' social cognition were assessed using gold standard questionnaires. Our results indicated that the manipulation of instructions had a minor effect on the exaggeration of amplitude during pantomime. We reported a link between the social cognition score and the amplitude in the Others condition for the hammer, which suggests that social cognitive processes could take part in pantomime production in some conditions. Nevertheless, this result does not alter our conclusion that social cognitive processes might be far from necessary for pantomime production.

Comparing mnemonic effects of iconic gestures and pictures on word memory

Previous studies using intermodal semantic priming have found that gestures improve language memory. In the present study, we ask whether the inherent characteristics of representative gestures (iconic gestures) facilitate word memory, or it is simply the semantic content shared with the words. Two analogous experiments were carried out presenting iconic gestures, pictures, or null primes to target words (nouns and action verbs). In Experiment 1, participants performed a free word recall task. In Experiment 2, the task was one of recognition. The results showed that participants recalled (Experiment 1) an equivalent number of words preceded by gestures or pictures compared with words alone, with no prime. However, a significantly higher number of words were recognised (Experiment 2) when they were primed by iconic gestures compared with the other two conditions, an advantage also found in reaction times (RTs) and both effects being larger in verbs than in nouns. These findings are discussed regarding the differences between recall and recognition processes as well as the particular characteristics of representative gestures.

Is motor activity the key to the observation-inflation effect? The role of action simulation

Observing others performing an action can lead to false memories of self-performance - the observation-inflation effect. The action simulation hypothesis proposes that an action simulation caused by people's observation of an action is the key reason for this effect. Previous studies have inconsistent views of this hypothesis. In the present study, we re-examined the role of action simulation and discussed the key aspects of the mental processes associated with it. We examined the hypotheses that (a) the magnitude of the observation-inflation effect would decrease as the action simulation was impeded and (b) the magnitude of the observation-inflation effect would not be significantly different in conditions in which participants watched either a part of a video or a full video. The results are consistent with the hypotheses. This study provides strong evidence that action simulation influences the generation of observation-inflation effects and that the process is continuous and can refer to further action information.

Integrative representation of semantic and motor information underlies the enactment effect in memory for actions

The present study adopted the retrieval-induced forgetting (RIF) effect to determine whether semantic representation might favour the enactment effect, in which noun-verb phrases are remembered better by enacting during learning (subject-performed tasks, SPTs) than by studying verbally (verbal tasks, VTs). Experiment 1 controlled the semantic category to investigate the RIF effect in SPT vs. VT conditions. The RIF effect was similar irrespective of the mode of encoding (SPT vs.VT), indicating that semantic representation was not the main factor for favouring the enactment effect. Furthermore, Experiment 2 added motor physical properties to simultaneously control the semantic category and one category by motor features. The results of Experiment 2 showed stronger cooperative representation of semantic and motor information under the VT condition, indicating that the processing of action memory may be conceptual.

The Effects of Language and Semantic Repetition on the Enactment Effect of Action Memory

Humans exhibit enhanced memory performance when information is encoded by physically enacting it, as opposed to passively reading or hearing the same information; an effect referred to as "enactment effect." The present study explored the effects of language (native vs. non-native) and semantic repetition (repeated vs. non-repeated) on the enactment effect in action memory. Forty-eight subjects learned action phrases either by enacting or by reading the items. Results showed (i) better memory for enacted phrases, (ii) better memory for non-native repeated phrases that were only read, (iii) no difference in memory between repeated and non-repeated phrases that were enacted, and (iv) that semantic repetition affected memory of phrases that were read but not of those that were enacted. Partly in line with the multimodal theory, findings support that enacting action phrases can enhance item-specific processing and that this is insensitive to cognitive strategies like semantic repetition.

The role of motor context in the beneficial effects of hand gesture on memory

Viewing co-speech hand gestures with spoken phrases enhances memory for phrases, as compared to when the phrases are presented without gesture. Prior work investigating the mechanism underlying the effect of gesture on memory has implicated engagement of the motor system; when the hands are engaged in an unrelated motor task when viewing gesture, the beneficial effect of gesture is absent. However, one alternative interpretation of these findings is that the beneficial effect of gesture disappears due to mismatched contexts at encoding and retrieval: The hands are engaged during either encoding or retrieval, but not during both stages. Here we examined whether matching the motor context at encoding and retrieval plays a role in the beneficial effect of gesture on memory during a phrase recall task. Participants were presented with phrases that were viewed with and without gesture. Participants were assigned to one of four conditions that determined whether they would complete an unrelated motor task at (1) encoding only, (2) retrieval only, (3) both encoding and retrieval, or (4) neither. During stages in which they were not completing a motor task, participants' hands were in their laps. We found that gesture enhanced memory for phrases both when participants engaged in an unrelated motor task at encoding and retrieval and when they did not complete the motor task during either stage. Furthermore, phrases observed with gesture were more likely to be paraphrased than to be recalled literally. Together, these findings demonstrate that gesture can enhance memory even when the motor system is engaged in another task, as long as that same task is performed at retrieval.

The beneficial effect of a speaker's gestures on the listener's memory for action phrases: The pivotal role of the listener's premotor cortex

Memory for action phrases improves in the listeners when the speaker accompanies them with gestures compared to when the speaker stays still. Since behavioral studies revealed a pivotal role of the listeners' motor system, we aimed to disentangle the role of primary motor and premotor cortices. Participants had to recall phrases uttered by a speaker in two conditions: in the gesture condition, the speaker performed gestures congruent with the action; in the no-gesture condition, the speaker stayed still. In Experiment 1, half of the participants underwent inhibitory rTMS over the hand/arm region of the left premotor cortex (PMC) and the other half over the hand/arm region of the left primary motor cortex (M1). The enactment effect disappeared only following rTMS over PMC. In Experiment 2, we detected the usual enactment effect after rTMS over vertex, thereby excluding possible nonspecific rTMS effects. These findings suggest that the information encoded in the premotor cortex is a crucial part of the memory trace.