Social Requests and Social Affordances: How They Affect the Kinematics of Motor Sequences during Interactions between Conspecifics

The present study aimed at determining whether and what factors affect the control of motor sequences related to interactions between conspecifics. Experiment 1 demonstrated that during interactions between conspecifics guided by the social intention of feeding, a social affordance was activated, which modified the kinematics of sequences constituted by reaching-grasping and placing. This was relative to the same sequence directed to an inanimate target. Experiments 2 and 4 suggested that the related-to-feeding social request emitted by the receiver (i.e. the request gesture of mouth opening) is prerequisite in order to activate a social affordance. Specifically, the two experiments showed that the social request to be fed activated a social affordance even when the sequences directed towards a conspecific were not finalized to feed. Experiment 3 showed that moving inside the peripersonal space of a conspecific, who did not produce any social request, marginally affected the sequence. Finally, experiments 5 and 6 indicated that the gaze of a conspecific is necessary to make a social request effective at activating a social affordance. Summing up, the results of the present study suggest that the control of motor sequences can be changed by the interaction between giver and receiver: the interaction is characterized by a social affordance that the giver activates on the basis of social requests produced by the receiver. The gaze of the receiver is a prerequisite to make a social request effective

Do Postures of Distal Effectors Affect the Control of Actions of Other Distal Effectors? Evidence for a System of Interactions between Hand and Mouth

The present study aimed at determining whether, in healthy humans, postures assumed by distal effectors affect the control of the successive grasp executed with other distal effectors. In experiments 1 and 2, participants reached different objects with their head and grasped them with their mouth, after assuming different hand postures. The postures could be implicitly associated with interactions with large or small objects. The kinematics of lip shaping during grasp varied congruently with the hand posture, i.e. it was larger or smaller when it could be associated with the grasping of large or small objects, respectively. In experiments 3 and 4, participants reached and grasped different objects with their hand, after assuming the postures of mouth aperture or closure (experiment 3) and the postures of toe extension or flexion (experiment 4). The mouth postures affected the kinematics of finger shaping during grasp, that is larger finger shaping corresponded with opened mouth and smaller finger shaping with closed mouth. In contrast, the foot postures did not influence the hand grasp kinematics. Finally, in experiment 5 participants reached-grasped different objects with their hand while pronouncing opened and closed vowels, as verified by the analysis of their vocal spectra. Open and closed vowels induced larger and smaller finger shaping, respectively. In all experiments postures of the distal effectors induced no effect, or only unspecific effects on the kinematics of the reach proximal/axial component. The data from the present study support the hypothesis that there exists a system involved in establishing interactions between movements and postures of hand and mouth. This system might have been used to transfer a repertoire of hand gestures to mouth articulation postures during language evolution and, in modern humans, it may have evolved a system controlling the interactions existing between speech and gestures

Speech and gesture: functional properties of the systems responsible for their interactions

La presente tesi si propone di studiare le caratteristiche funzionali del sistema responsabile dei nessi motori tra mano e bocca (sistema di doppi comandi alla mano e alla bocca), con lo scopo ultimo di comprendere se esso possa essere, più o meno direttamente, responsabile delle interazioni esistenti tra gesto (manuale) e parlato. A questo scopo, saranno descritti e discussi due studi che utilizzano l’analisi cinematica del movimento e l’analisi dello spettro della voce dei partecipanti (destrimani, lingua nativa italiano). Il primo studio mostrerà che posture della mano (destra) e della bocca, implicitamente connesse all’interazione con oggetti di diverse dimensioni, influenzano rispettivamente le configurazioni della bocca e della mano (destra), assunte durante l’esecuzione di una successiva prensione. Il dato mostrante che la postura di un effettore è in grado di influenzare il successivo movimento dell’altro esclude che i nessi tra mano e bocca siano dovuti a un semplice meccanismo di accoppiamento temporale tra i movimenti dei due effettori distali. Uniti al risultato mostrante che le interazioni osservate sono specifiche per mano e bocca, e non estendibili ad altri effettori distali (es. piede), questi dati corroborano l’ipotesi che il sistema di doppi comandi alla mano e alla bocca possa essere alla base delle reciproche interazioni esistenti tra gesto e parola, se si considera che essi sono costituiti sia da posture che da movimenti. Infine, il primo studio mostrerà che posture implicanti una maggiore o minore apertura della bocca interna, associata alla produzione di vocali aperte e chiuse (/a/ e /i/), influenzano anch’esse la successiva prensione manuale. Anche questo risultato sembra confermare l’ipotesi che il sistema di doppi comandi alla mano e alla bocca possa essere alla base delle interazioni osservate tra gesto e parlato e che esso possa essere coinvolto nell’evoluzione di un sistema comunicativo verbale, a partire da un sistema comunicativo di tipo gestuale. Il secondo studio partirà dai dati appena descritti e compirà un passo avanti: per stabilire la natura delle interazioni tra gesti e parole è, infatti, necessario chiarire se posture della mano esprimenti gesti dotati di significato influenzino la produzione di unità fonemiche (es. vocali) e se questi eventuali effetti siano presenti anche durante la produzione di parole, il cui significato corrisponde a quello del gesto. Pertanto, nel secondo studio si analizzeranno gli effetti di gesti rappresentazionali (ossia, che indicano una proprietà fisica dell’oggetto di conversazione), sia uni manuali che bi manuali e il cui significato si riferisce a “grande” o “piccolo”, sulla pronuncia delle vocali /a/ e /i/ prodotte isolatamente o all’interno delle parole /grande/ e /piccolo/. I risultati dello studio confermeranno l’esistenza di nessi funzionali tra posture gestuali della mano destra e produzione di vocali, e proveranno nuovamente che tali interazioni sono dovute all’attività del sistema di doppi comandi alla mano e alla bocca. In più, i risultati del secondo studio riveleranno la presenza d’interazioni reciproche tra gesti e parole, dovute verosimilmente all’attività di un diverso sistema, che lega i due segnali grazie alla costruzione di una rappresentazione del loro significato, comune a tutti gli effettori usati (una mano, due mani e bocca). Quest’ultimo sistema è probabilmente più distribuito di quello di doppi comandi alla mano e alla bocca, anche se, presumibilmente, esso ne è il precursore. I legami tra gesto e parola sembrano stabiliti dal sistema in base a processi di categorizzazione semantica, mentre le interazioni tra posture della mano destra e produzione di vocali sembrano essere di natura più squisitamente motoria. Complessivamente, i risultati degli studi che saranno descritti nella presente trattazione, oltre ad approfondire le caratteristiche funzionali del sistema di doppi comandi alla mano e alla bocca, mostreranno che esso è parzialmente coinvolto nelle reciproche interazioni tra gesto e parlato, nel senso che, probabilmente, è stato il tramite iniziale per mezzo del quale tali reciprocità si sono stabilite.This thesis is aimed at determining the functional properties of the system responsible for interactions between hand and mouth movements (dual hand-mouth motor command system). Furthermore, I am interested in discovering if this same system can also be involved in establishing the interactions existing between speech and gesture. To this purpose, I will describe and discuss two kinematic studies, in which I also used vocal spectra analysis of right-handed, Italian native speaker participants. The first study will show that postures of hand and mouth, implicitly linked to interactions with different sized object, can affect the kinematics of consequent mouth and hand grasps, respectively. This result rules out the possibility that interactions between hand and mouth are due to a simple temporal coupling mechanism between synchronic movements of the two effectors. Furthermore, the study will reveal that the observed relation between distal effectors is specific for hand and mouth. All these data are in accordance to the hypothesis that the dual hand-mouth motor command system is precursor of the system relating speech and gesture, since they are also made up of hand and mouth postures, and not only of hand and mouth movements. Moreover, and according to this view, the first study will show that postures of the internal mouth, related to production of open and closed vowels (/a/ and /i/), also affect the finger shaping during the consequent hand grasp. These data support the hypothesis that the dual hand-mouth motor command system could be involved in evolution of a communication system based on speech from a system based on manual gesture. The second study of the present thesis will try to understand what kind of relation links speech and gesture. To this purpose, I compared the effects of representational manual gestures, expressing the meaning of “large” and “small”, on pronunciation of vowels /a/ and /i/, either isolated or included in the words ”grande” (large) or “piccolo” (small). The results of this study will confirm the activity of the dual hand-mouth motor command system in establishing relations between hand posture (gesture production) and isolated vowel pronunciation. Moreover, the results will reveal the activity of another system that links speech (words) and gesture, by means of categorization processes of their meaning. Probably, the dual hand-mouth motor command system is precursor of the system relating speech and gesture, and it establishes motor functional relations between hand and mouth movements. On the other hand, the system that relates speech and gesture is probably more distributed, and its activity is based on categorization processes that provide a more abstract representation of the meaning of mouth and hand postures and movements, related to speech and gesture production

Three-Dimensional Kinematic Analysis of Prehension Movements in Young Children with Autism Spectrum Disorder: New Insights on Motor Impairment

The study was aimed at better clarifying whether action execution impairment in autism depends mainly on disruptions either in feedforward mechanisms or in feedback-based control processes supporting motor execution. To this purpose, we analyzed prehension movement kinematics in 4- and 5-year-old children with autism and in peers with typical development. Statistical analysis showed that the kinematics of the grasp component was spared in autism, whereas early kinematics of the reach component was atypical. We discussed this evidence as suggesting impairment in the feedforward processes involved in action execution, whereas impairment in feedback-based control processes remained unclear. We proposed that certain motor abilities are available in autism, and children may use them differently as a function of motor context complexity

Gaze direction and request gesture in social interactions.

One of the most important faculties of humans is to understand the behaviour of other conspecifics. The present study aimed at determining whether, in a social context, request gesture and gaze direction of an individual are enough to infer his/her intention to communicate, by searching for their effects on the kinematics of another individual's arm action. In four experiments participants reached, grasped and lifted a bottle filled of orange juice in presence of an empty glass. In experiment 1, the further presence of a conspecific not producing any request with a hand and gaze did not modify the kinematics of the sequence. Conversely, experiments 2 and 3 showed that the presence of a conspecific producing only a request of pouring by holding the glass with his/her right hand, or only a request of comunicating with the conspecific, by using his/her gaze, affected lifting and grasping of the sequence, respectively. Experiment 4 showed that hand gesture and eye contact simultaneously produced affected the entire sequence. The results suggest that the presence of both request gesture and direct gaze produced by an individual changes the control of a motor sequence executed by another individual. We propose that a social request activates a social affordance that interferes with the control of whatever sequence and that the gaze of the potential receiver who held the glass with her hand modulates the effectiveness of the manual gesture. This paradigm if applied to individuals affected by autism disorder can give new insight on the nature of their impairment in social interaction and communication

Gaze Direction and Request Gesture in Social Interactions

One of the most important faculties of humans is to understand the behaviour of other conspecifics. The present study aimed at determining whether, in a social context, request gesture and gaze direction of an individual are enough to infer his/her intention to communicate, by searching for their effects on the kinematics of another individual's arm action. In four experiments participants reached, grasped and lifted a bottle filled of orange juice in presence of an empty glass. In experiment 1, the further presence of a conspecific not producing any request with a hand and gaze did not modify the kinematics of the sequence. Conversely, experiments 2 and 3 showed that the presence of a conspecific producing only a request of pouring by holding the glass with his/her right hand, or only a request of comunicating with the conspecific, by using his/her gaze, affected lifting and grasping of the sequence, respectively. Experiment 4 showed that hand gesture and eye contact simultaneously produced affected the entire sequence. The results suggest that the presence of both request gesture and direct gaze produced by an individual changes the control of a motor sequence executed by another individual. We propose that a social request activates a social affordance that interferes with the control of whatever sequence and that the gaze of the potential receiver who held the glass with her hand modulates the effectiveness of the manual gesture. This paradigm if applied to individuals affected by autism disorder can give new insight on the nature of their impairment in social interaction and communication

Intolerance of Uncertainty in Eating Disorders: A Systematic Review and Meta-Analysis

Intolerance of uncertainty is an empirically supported transdiagnostic construct that may have relevance in understanding eating disorders. We conducted a meta-analysis and systematic review of intolerance of uncertainty in eating disorders using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We calculated random-effects standardised mean differences (SMD) for studies utilising the Intolerance of Uncertainty Scale (IUS) and summarised additional studies descriptively. Women with eating disorders have significantly higher IUS scores compared with healthy controls (SMD = 1.90; 95% C.I. 1.24 to 2.56; p < 0.001). Post hoc meta-analysis revealed significant differences when comparing women with anorexia nervosa with controls (SMD = 2.16; 95% C.I. 1.14 to 3.18; p < 0.001) and women with bulimia nervosa with controls (SMD = 2.03; 95% C.I. 1.30 to 2.75; p < 0.001). Our synthesis of findings suggests that intolerance of uncertainty may represent a vulnerability and maintenance factor for eating disorders and potential target of cognitive, behavioural, interoceptive and affective symptoms. Copyright © 2017 John Wiley & Sons, Ltd and Eating Disorders Association