No-touch Condition Research Articles

Fingertip light touch contact increases anteroposterior limits of stability in healthy young and older adults

BackgroundThe limit of stability (LoS), an index of stance balance ability, is reduced in older adults. Although contacting an earth-fixed external surface through fingertips’ light touch improves older adults’ stance balance control, its effects on the LoS in this population are unclear. Research questionDoes light touch increase the LoS and reduce postural sway in the LoS? MethodsThis study included 20 young adults (11 women and 9 men, mean age = 20.6 years) and 15 community-dwelling older adults (8 women and 7 men, mean age = 74.5 years). The position and path length of the center of pressure (CoP) during quiet standing (QS) and the anterior and posterior LoS (A-LoS and P-LoS, respectively) were measured using a force platform under two touch conditions (no-touch condition and light-touch condition). In light-touch condition, participants placed the tip of their dominant index finger on a load cell, which had an applied force of <1 N. ResultsIn both touch conditions, the older group had a more limited CoP position in the anteroposterior LoS and a longer CoP path length in the QS and LoS than the younger group. In both participant groups, the light-touch condition showed a wider CoP position in the anteroposterior LoS and a shorter CoP path length in the QS and LoS than the no-touch condition. SignificanceLight touch increases the anteroposterior LoS and decreases postural sway in the LoS. Therefore, contacting an external object by fingertips’ light touch may be an effective training protocol to increase the LoS in older adults.

Real human touch: performer-facilitated touch enhances presence and embodiment in immersive performance

Despite being an embodied medium, virtual reality (VR) prioritizes vision and sound over the other senses. While touch has been demonstrated to foster a sense of presence and embodiment, most haptic research in VR focuses on uncanny vibration motors or limited experiences of touch with simple props. Meanwhile, immersive performances such as Eve 3.0 incorporate performer-facilitated touch in novel ways to evoke a complete and social experience of human touch in VR. In response, we conducted a mixed-methods study to investigate the experience of performer-facilitated touch in a 360° video segment from the immersive performance Eve 3.0. Using a 3 × 2 factorial design, we compared touch from a diary prop and performer in festival and laboratory settings. We found that performer-facilitated touch increased realistic behaviours and questionnaire measures of social presence, embodiment, and tactile realism. The setting also had a significant effect with festival participants demonstrating significantly more behaviours indicating presence, particularly in the no-touch condition. Participant descriptions reveal that in addition to touch, a rich narrative and vivid visuals of social interaction were just as important in immersing participants in the experience and making them feel present. We find that participant experiences are a co-creation situated at the intersection of artefact and context that require a willing suspension of disbelief. The authentic setting and performance artefact afforded a deep understanding of the rich and complex experience of human touch in immersive performance.

Effects of passive interpersonal light touch during walking on postural control responses: An exploratory study

The effects of passive interpersonal light touch (PILT) on postural stability can be observed through improved postural coordination through haptic feedback from the contact provider to the contact receiver while walking. It is unclear, however, whether PILT affects the contact receiver's detailed physical responses, such as muscle activity, body sway, and joint movements. In this study, surface electromyography and an inertial measurement unit were used simultaneously to explore changes in walking speed and control responses induced by PILT. We evaluated fourteen healthy participants for their walking speed and physical responses under two walking conditions: no-touch (NT) and PILT. As a physical response during walking, we measured muscle activity (rectus femoris, semitendinosus, tibialis anterior, and soleus muscles), body sway (pelvis and neck), and joint angles (direction of hip, knee, and ankle joint movements). In PILT condition, fingertip contact force was measured while the contact provider touched the third level of the recipient's lumbar spine. In comparison with the NT condition, PILT condition increased walking speed and decreased body sway on neck position. There were significant correlations between walking speed and neck sway regarding NT and PILT change values. Passive haptic information to the contact receiver may assist in the smooth shift of the center of gravity position during gait through interpersonal postural coordination. These findings suggest that PILT may provide an efficient and stable gait.

Effects of light finger touch on the regularity of center-of-pressure fluctuations during quiet bipedal and single-leg postural tasks

BackgroundThe use of extra sources of sensory information associated with light fingertip touch to enhance postural steadiness has been associated with increased attentional demands, whereas the regularity of center of pressure (COP) fluctuations has been interpreted as a marker of the amount of attention invested in posture control. Research questionThis study addressed whether increased attentional demands associated with postural tasks involving light finger touch might be reflected by measures of COP regularity. MethodsThe experiments involved quiet bipedal stance (n = 8 participants) and single-legged stance (n = 14 participants). Each participant was instructed to stand as quietly as possible on a force plate, either touching an external rigid surface (applied force < 1 N, light touch condition), or not (no touch condition). Postural steadiness was assessed by traditional COP measurements (COP Area, RMS, and velocity), whereas the regularity of postural sway was based on estimates of the sample entropy (SaEn) of the COP time series. ResultsTraditional parameters of postural sway and COP regularity (inversely related to SaEn COP measurements) were reduced during the touch conditions as compared to the no-touch conditions, for both bipedal quiet stance and single-legged stance. Decreased COP regularity with light touch was mainly reflected in the direction of the largest postural sway (i.e. in the sagittal plane for bipedal stance and in the frontal plane for single-legged stance). SignificanceThe present results suggest that actively touching an external surface with the fingertip, besides increasing postural steadiness, generated an externally oriented (presumably cognitive-dependent) focus of attention, so that participants invested less attention on the postural task per se (as suggested by increased SaEn), which might be associated with a more “automatic” control of posture.

Universality without uniformity – infants’ reactions to unresponsive partners in urban Germany and rural Ecuador

Previous studies based on non-WEIRD (Western, Educated, Industrialized, Rich, and Democratic) samples provide initial evidence that the still-face effect is universal. Based on the assumption that – independent of their cultural niches – infants share some fundamental expectations of social interactions, we put forth the assumption that a universal response exists for when a social interaction is interrupted. At the same time, we hypothesized that the size of the effect depends on the typicality of the interaction that precedes the adult partners’ interruption. To test these hypotheses, we conducted the Still-Face Paradigm (SFP) with infants (3- and 4.5-month-olds) from two cultural milieus, namely Münster (urban Germany) and the Kichwa ethnic group from the northern Andes region (rural Ecuador), as these contexts presumably offer different ways of construing the self that are associated with different parenting styles, namely distal and proximal parenting. Furthermore, we developed a paradigm that comes much closer to the average expected environment of Kichwa infants, the “No-Touch Paradigm” (NTP). Overall, the results support our initial hypothesis that the still-face effect is universal. Moreover, infants from both cultural milieus responded to the no-touch condition with a change in negative affect. At the same time, some of the infants’ responses were accentuated in a culture-specific way: Kichwa infants had a stronger response to an interruption of proximal interaction patterns during the NTP. While our findings underline infants’ universal predisposition for face-to-face interaction, they also suggest that cultural differences in internalized interactions do influence infant behavior and experience and, in turn, development.

Characteristics of postural control during fixed light-touch and interpersonal light-touch contact and the involvement of interpersonal postural coordination.

Haptic feedback by light touch with a fingertip influences the postural control of the human body by postural orientation. Postural control might therefore differ depending on the characteristics of the contacting object. The main experimental targets of contact have been a fixed object (fixed light touch: FLT) and an individual (interpersonal light touch: ILT), but the postural control characteristics of FLT and ILT have not been directly compared within the same study. Nor has there been a study comparing frequency characteristics in these conditions. We hypothesized that (1) the frequency of postural sway would be higher in FLT and that no such change would be observed in ILT, and (2) the interpersonal postural coordination that is specific to ILT, i.e., sway that resembles the other person's sway, would be observed in the low-frequency component (≤0.4 Hz) rather than the high-frequency component (>0.4 Hz). We applied a closed-eyes tandem stance by adult subjects as the standard condition, and the center of pressure was measured when they performed four standing conditions: no-touch, FLT, stable ILT with a bipedal partner, and unstable ILT with a tandem partner. The results demonstrated that the FLT condition and both the stable and unstable ILT conditions also stabilized the posture, but the stability was superior in the FLT condition. Further, the difference in postural stability depending on the axis is not clear in any conditions for velocity, whereas for amplitude, stabilization by contact is more easily captured in the medio-lateral (ML) axis than in the anterior-posterior (AP) axis. The mean power frequency (MPF) in the FLT condition was higher than the no-touch condition, and the stable ILT condition in the ML axis and was higher than any other conditions in the AP axis. Moreover, the stable ILT condition in both axes was not significantly different from the no-touch condition. The unstable ILT condition in the AP axis was also not significantly different, though the ML axis was higher than the no-touch condition. The interpersonal postural coordination in both the stable and unstable ILT conditions was observed in the low-frequency component (except for the ML axis of the unstable ILT condition) and not in the high-frequency component. These results support our hypotheses and suggest that although FLT and ILT exert effects on reducing postural sway to some certain extent, in actuality, these conditions result in different postural controls in the frequency domain due to postural coordination based on the low-frequency component.

The effect of visual and tactile information in motor preparation of climbing

ABSTRACT In rock climbing, an appropriate motor preparation to a given climbing hold(s) is crucial for a fluent climbing. We investigated the influence of visual-tactile information in motor preparation of climbing, particularly the effect of the number of the holds and the tactile input of an actual hold was examined. Reaction times (RTs) under the priming paradigm were compared for climbers and non-climbers. Participants were asked to respond to a visual target (left or right arrow) after the presentation of a picture of a single climbing hold (Single-Prime condition: SP) or two holds (Double-Prime condition: DP). Before commencing each trial block, the participants were also asked to touch or watch an actual hold (touch /no-touch condition). The response based on the congruity between the orientation of the hold and that of the arrow was categorised as either congruent or incongruent. An ANOVA performed on the RTs showed the congruency effect, but this was observed only in the non-climbers. An additional analysis revealed a marginally significant climbing experience-related interaction. In the high-experienced climbers, the RTs in the touch condition were slower than those in the no-touch condition but this was only in the SP condition. In the no-touch condition, the RTs of DP were slower than those of SP. These results therefore suggest that the motor preparation is mediated by visual and tactile inputs of a given hold. The time needed for motor preparation, particularly in highly experienced climbers, may be modulated by the representational complexity of climbing movements through tactile information. Highlight The number of the holds visually presented affected the motor preparation. The tactile input of the climbing hold modulated the motor preparation only in the highly experienced climbers. Our findings imply that climbing-specific context (i.e. combination of the given holds) and experience (i.e. action competency) are involved in the motor preparation of climbing.

Force Control on Fingertip Using EMS to Maintain Light Touch.

Light touch on a rigid surface with minimal force below a specific threshold reduces postural sway by providing additional sensory cues from the fingertips. The feasibility of maintaining light touch depends on subject characteristics and task difficulty. Therefore, we introduce a method of maintaining light touch by using electrical muscle stimulation (EMS). We applied it in a single-leg standing task involving healthy adult subjects. The subjects stood upright in a single-leg stance on a firm surface and on foam rubber (FR), respectively, under three conditions: no touch (NT, NT-FR), light touch without EMS (LT, LT-FR), and light touch in which EMS was applied based on the contact force (LT-EMS, LT-EMS-FR). The results showed that the force control by EMS helped maintain light touch and reduce postural sway compared with the no-touch condition. The amplitude of postural sway under the touch condition with EMS was equivalent to that under the touch condition without EMS.

The effects of light touch cue on gait initiation in patients with Parkinson's disease

IntroductionOne of the common impairments in patients with Parkinson's disease (PD) is disturbance of gait initiation. A light touch cue improves postural stability in patients with PD. Little is known about the effects of a light touch cue on gait initiation. This study investigated the effects of a light touch on gait initiation in patients with PD. MethodsThis study was a cross-sectional study design. Sixteen patients with PD (Hoehn & Yahr stage 2–3) participated in the study and were evaluated two gait conditions (no touch (NT) and light touch (LT) conditions). Gait initiation was divided into 5 events including event A, B, C, D, and E. Outcome measures included maximum center of pressure (COP) displacement and velocity in anteroposterior (AP) and mediolateral (ML) directions, and the first step time. ResultsParticipants with LT had greater COP displacement compared with the NT condition in all events of gait initiation except COP-AP displacement in event D. Additionally, the COP velocity in LT condition was faster than the NT condition in COP-ML velocity in event A, COP-AP velocity in event B, COP-AP velocity and COP-ML velocity in event C. Moreover, participants with LT presented significantly shorter the first step time than the NT condition. ConclusionsThese findings demonstrated that a light touch cue improved gait initiation in patients with PD by increased weight shifting to initial stance limb, increased postural stability of stance limb, increased velocity of weight transfer toward stance limb, and a shortened first step time.

Social touch alters newborn monkey behavior

In humans, infants respond positively to slow, gentle stroking—processed by C-tactile (CT) nerve fibers—by showing reductions in stress and increases in eye contact, smiling, and positive vocalizations. More frequent maternal touch is linked to greater activity and connectivity strength in social brain regions, and increases children’s attention to and learning of faces. It has been theorized that touch may prime children for social interactions and set them on a path towards healthy social cognitive development. However, less is known about the effects of touch on young infants’ psychological development, especially in the newborn period, a highly sensitive period of transition with rapid growth in sensory and social processing. It remains untested whether newborns can distinguish CT-targeted touch from other types of touch, or whether there are benefits of touch for newborns’ social, emotional, or cognitive development. In the present study, we experimentally investigated the acute effects of touch in newborn monkeys, a common model for human social development. Rhesus macaques (Macaca mulatta), like humans, are highly social, have complex mother-infant interactions with frequent body contact for the first weeks of life, making them an excellent model of infant sociality. Infant monkeys in the present study were reared in a neonatal nursery, enabling control over their early environment, including all caregiver interactions. One-week-old macaque infants (N = 27) participated in three 5-minute counter-balanced caregiver interactions, all with mutual gaze: stroking head and shoulders (CT-targeted touch), stroking palms of hands and soles of feet (Non-CT touch), or no stroking (No-touch). Immediately following the interaction, infants watched social and nonsocial videos and picture arrays including faces and objects, while we tracked their visual attention with remote eye tracking. We found that, during the caregiver interactions, infants behaved differently while being touched compared to the no-touch condition, irrespective of the body part touched. Most notably, in both touch conditions, infants exhibited fewer stress-related behaviors—self-scratching, locomotion, and contact time with a comfort object—compared to when they were not touched. Following CT-targeted touch, infants were faster to orient to the picture arrays compared to the other interaction conditions, suggesting CT-targeted touch may activate or prime infants’ attentional orienting system. In the No-touch condition infants attended longer to the nonsocial compared to the social video, possibly reflecting a baseline preference for nonsocial stimuli. In contrast, in both touch conditions, infants’ looked equally to the social and nonsocial videos, suggesting that touch may influence the types of visual stimuli that hold infants’ attention. Collectively, our results reveal that newborn macaques responded positively to touch, and touch appeared to influence some aspects of their subsequent attention, although we found limited evidence that these effects are mediated by CT fibers. These findings suggest that newborn touch may broadly support infants’ psychological development, and may have early evolutionary roots, shared across primates. This study illustrates the unique insight offered by nonhuman primates for exploring early infant social touch, revealing that touch may positively affect emotional and attentional development as early as the newborn period.

The Role of Physical Activity and Touch in Children’s Social Bonding

Physical activity (PA) and touch, long known to facilitate interpersonal affiliation in adults and non-human primates, are common elements of children’s free play. However, no research has examined how children’s play involving PA and touch is linked with social bonding (i.e., positive emotional states and behaviors that help create, maintain and characterize affiliation and attachment among individuals). This paper reports on two novel studies designed to explore these links in children’s play. In two studies, we investigated associations between PA, touch and prosociality in 5-to-8-year-old children. In a naturalistic observation study (N = 50), we assessed the amount of PA, smiling/laughing, touch, and prosociality in children’s play behavior during school breaks. PA levels were also measured indirectly via heart rate monitors (HRM). The findings revealed that observed-PA was associated with the amount of smiling/laughing. PA (observed and HRM) was also associated with the amount of touch. In a second study (N = 84), we experimentally tested the effect of touch on helping behavior in the context of physically-active play. In pairs, children ran to collect felt shapes which they placed either onto each other (touch condition) or onto a board (no-touch condition). Subsequent helping behavior was assessed in a separate task. There was a non-significant trend towards more helping in the touch condition. We discuss the findings in terms of the significance of PA and touch for social bonding in childhood and offer suggestions for future research in this underexplored area.

Tune to touch: Affective touch enhances learning of face identity in 4-month-old infants

Touch provides more than sensory input for discrimination of what is on the skin. From early in development it has a rewarding and motivational value, which may reflect an evolutionary mechanism that promotes learning and affiliative bonding. In the present study we investigated whether affective touch helps infants tune to social signals, such as faces. Four-month-old infants were habituated to an individual face with averted gaze, which typically does not engage infants to the same extent as direct gaze does. As in a previous study, in the absence of touch, infants did not learn the identity of this face. Critically, 4-month-old infants did learn to discriminate this face when parents provided gentle stroking, but they did not when they experienced a non-social tactile stimulation. A preliminary follow-up eye-tracking study (Supplementary material) revealed no significant difference in the visual scanning of faces between touch and no-touch conditions, suggesting that affective touch may not affect the distribution of visual attention, but that it may promote more efficient learning of facial information.

Affect contagion between mothers and infants: Examining valence and touch.

Mothers and their babies represent one of the closest dyadic units and thus provide a powerful paradigm to examine how affective states are shared, and result in, synchronized physiologic responses between two people. We recruited mothers and their 12- to 14-month-old infants (Ndyads = 98) to complete a lab study in which mothers were initially separated from their infants and assigned to either a low-arousal positive/relaxation condition, intended to elicit parasympathetic nervous system (PNS) reactivity, or a high-arousal negative/stress task, intended to elicit sympathetic nervous system (SNS) reactivity. Upon reunion, infants were placed either on their mothers' laps (touch condition) or in a high chair next to the mother (no-touch condition). We then examined if the babies SNS and/or PNS responses changed from their baseline levels and how the dyads' physiological responses-both PNS and SNS responses-synchronized over time as a function of mothers' affect manipulation and touch condition. Three noteworthy findings were observed. First, infants of mothers assigned to the relaxation task showed greater PNS increases and PNS covariation. Second, infants of mothers assigned to the stress task showed stronger SNS covariation with their mothers over time. Finally, infants who sat on their mothers' laps (i.e., touch condition) showed stronger SNS covariation than those in the no-touch condition. Taken together, these results suggest that mothers' affective states-low-arousal positive states as well as high-arousal negative states-can be "caught" by their infants, and that touch can play a critical role in stress contagion. (PsycINFO Database Record

A light fingertip touch reduces postural sway in children with autism spectrum disorders

This study examined the effects of a light fingertip touch on postural control in children with autism spectrum disorders (ASD) and typically developing children (TDC). MethodsWe recruited 16 children with ASD (age=11.041±1.275), and 16 TDC (age=10.966±1.166 years). A force platform measured postural sway in the anteroposterior (AP) and mediolateral (ML) directions under light fingertip touch (LT) and no touch (NT) conditions, with both eyes open (EO) and both eyes closed (EC). As a summary of the experimental conditions, ML sway was significantly greater in the ASD group than in the TDC group. Also, results showed a significant reduction in postural sway in the ML direction in the LT condition compared with the NT condition. These effects applied to both the EO and EC conditions. Lastly, the reduction in ML sway between the NT and LT conditions was significantly greater in the ASD than the TDC group. ConclusionThe effects of a light fingertip touch on reducing postural sway appear more efficient in children with ASD compared with TDC. These findings suggest that a light fingertip touch may be of clinical and practical importance, and provides a useful means of enhancing postural stability in children with ASD.

The Virtual Midas Touch: Helping Behavior After a Mediated Social Touch.

A brief touch on the upper arm increases people's altruistic behavior and willingness to comply with a request. In this paper, we investigate whether this Midas touch phenomenon would also occur under mediated conditions (i.e., touching via an arm strap equipped with electromechanical actuators). Helping behavior was more frequently endorsed in the touch, compared to the no-touch condition, but this difference was not found to be statistically significant. However, a meta-analytical comparison with published research demonstrated that the strength of the virtual Midas touch is of the same magnitude as that of the Midas touch in unmediated situations. The present experiment, thus, provides empirical evidence that touch-like qualities can be attributed to electromechanical stimulation. This is important for the field of mediated social touch of which the design rationale is based on the assumption that mediated touch by means of tactile feedback technologies is processed in ways similar to real physical contact.

Increasing Compliance with a Request: Two Touches are More Effective than One

Touch procedures have been shown to increase the likelihood of compliance with requests. But the effect of subsequent touches following a classical touch procedure has not been investigated. It was predicted that two touches would lead to more compliance than one touch. 180 male and 180 female bystanders were asked to fill in a short or long questionnaire by a female confederate. They were touched by the confederate either once, twice, or not at all. Results showed that there was more compliance in the two-touch than in the one-touch condition, and when the participants were touched by the confederate. These findings support the hypothesis. Moreover, whereas participants were less likely to fill in the long questionnaire in the no-touch condition, touch procedures led to more compliance whatever the questionnaire length. Also, touch was more effective when a female confederate made the request to a male participant.

Light Finger Touch on the Upper Legs Reduces Postural Sway during Quasi-Static Standing

The purpose of this study was to test whether a light finger touch on one's own body (upper legs) reduces postural sway. Ten healthy males participated. In the first part of the study, the participants stood upright with their eyes closed on a force platform while ground reaction force data were collected. Two conditions differing in the placement of the arms and fingers were tested. In the no-touch condition, the participants kept their hands in loose fists. In the finger-touch condition, the participants lightly touched the lateral sides of the upper legs with all fingers. Postural sway measures were calculated from the ground reaction force data. In the second part of the study, the participants stood upright on a pneumatic balance disk while ground reaction force data were collected. Experimental and measurement protocols were identical to those used in the first part of the study. The results showed that light finger touch on the upper legs significantly reduced postural sway on the balance disk up to approximately 7%. The data from this study suggest that decreased postural sway due to finger contact may improve balance control during other standing tasks.

Two steps forward and one back: Learning to walk affects infants’ sitting posture

The transition from sitting to walking is a major motor milestone for the developing postural system. This study examined whether this transition to walking impacts the previously established posture (i.e., sitting). Nine infants were examined monthly from sitting onset until 9 months post-walking. Infants sat on a saddle-shape chair either independently or with their right hand touching a stationary contact surface. Postural sway was measured by sway amplitude, variability, area, and velocity of the center of pressure trajectory. The results showed that for all the postural measures in the no-touch condition, a peak before or at walk onset was observed in all the infants. At the transition age, when peak sway occurred, infants’ postural sway measures were significantly greater than at any other age. Further, infants’ postural sway was attenuated by touch only at this transition. We suggest that this transient disruption in sitting posture results from a process involving re-calibration of an internal model for the sensorimotor control of posture so as to accommodate the newly emerging bipedal behavior of independent walking.

Fingertip contact suppresses the destabilizing influence of leg muscle vibration.

Touch of the hand with a stationary surface at nonmechanically supportive force levels (<1 N) greatly attenuates postural sway during quiet stance. We predicted such haptic contact would also suppress the postural destabilization caused by vibrating the right peroneus brevis and longus muscles of subjects standing heel-to-toe with eyes closed. In experiment 1, ten subjects were tested under four conditions: no-vibration, no-touch; no-vibration, touch; vibration, no-touch; and vibration, touch. A hand-held physiotherapy vibrator (120 Hz) was applied approximately 5 cm above the malleolous to stimulate the peroneus longus and brevis tendons. Touch conditions involved contact of the right index finger with a laterally positioned surface (<1 N of force) at waist height. Vibration in the absence of finger contact greatly increased the mean sway amplitude of the center of pressure and of the head relative to the no-vibration, no-touch control condition (P < 0.001). The touch, no-vibration and touch-vibration conditions were not significantly different (P > 0.05) from each other and both had significantly less mean sway amplitude of head and of center of pressure than the other conditions (P < 0.01). In experiment 2, eight subjects stood heel-to-toe under touch and no-touch conditions involving 40-s duration trials of peroneus tendon vibration at different duty cycles: 1-, 2-, 3-, and 4-s ON and OFF periods. The vibrator was attached to the subject's leg and remotely activated. In the no-touch conditions, subjects showed periodic postural disruptions contingent on the duty cycle and mirror image rebounds with the offset of vibration. In the touch conditions, subjects were much less disrupted and showed compensations occurring within 500 ms of vibration onset and mirror image rebounds with vibration offset. Subjects were able to suppress almost completely the destabilizing influence of the vibration in the 3- and 4-s duty cycle trials. These experiments show that haptic contact of the hand with a stable surface can suppress abnormal proprioceptive and motor signals in leg muscles.

Infants' preference for touch stimulation in face-to-face interactions

Infant preference for social stimulation that included touch during a face-to-face situation with an adult was investigated. Ten 1.5- to 3.5-month-old infants ( M = 2.6, SD = .6) participated in a within-subjects repeated-measures design. Two treatment conditions were compared in an alternated, counterbalanced order with each infant. Under the touch treatment, the infant eye-contact responses were followed by continuous contingent adult smiling, cooing, and rubbing of the legs and feet. Under the no-touch treatment, the infant eye-contact responses were followed by contingent adult smiling and cooing, but not by touching. The results showed that, during the touch condition, infants emitted more eye contact and more smiles and vocalizations, and they spent less time crying and protesting compared with the no-touch condition. The results demonstrated that a social stimulus compound that included touching the infants functioned as a more effective reinforcer for infant eye-contact behavior than a stimulus compound that did not include touch.