Child-holding patterns and hemispheric bias

Artistic turns: laterality in paintings of kisses and embraces

Many lateral biases exist in human behavior, often implicit and not deliberated. Romantic kissing and embracing received experimental attention in the last three decades. We investigated laterality in paintings depicting these social interactions using two methodologies to assess whether painters depicted such biases and whether these biases could be due to observers' aesthetic preferences or painters' ability in portraying naturalistic interactions. In Study 1, we inspected about 190,000 artworks available online to classify leftward and rightward biases in romantic kisses and embraces. The comparison of 103 paintings depicting clearly lateralized interactions revealed a significant rightward bias in romantic kissing (66%) and a trend toward a leftward bias (62%) for embraces, aligning with naturalistic studies of human interactions. In Study 2, 128 participants expressed their aesthetic preference between the paintings selected in Study 1 and their vertically mirrored versions. A preference for the original paintings over their mirrored versions emerged, especially when presented in the upper portion of the screen, but no significant preference for the typical lateralization of kissing and embracing was found. These findings suggest that artists' alignment with naturalistic biases could be due to familiarity and exposure to asymmetric interactions rather than observers' aesthetic preferences.

The Role of Ethnic Prejudice in the Modulation of Cradling Lateralization

The left-cradling bias is the tendency to cradle an infant on the left side, regardless of the individuals' handedness, culture or ethnicity. Many studies revealed associations between socio-emotional variables and the left-side bias, suggesting that this asymmetry might be considered as a proxy of the emotional attunement between the cradling and the cradled individuals. In this study we examined whether adult females with high levels of prejudice toward a specific ethnic group would show reduced left-cradling preferences when required to cradle an infant-like doll with ethnical features of the prejudiced group. We manipulated the ethnicity of the cradled individual by asking 336 Caucasian women to cradle a White or a Black doll and then assessed their prejudice levels toward African individuals. Significant correlations were shown only in the Black doll group indicating that the more the prejudice toward Africans, the more the cradling-side preferences shifted toward the right. Furthermore, participants exhibiting low levels-but not those exhibiting high levels-of ethnic prejudice showed a significant left-cradling bias. These findings show that ethnic prejudice toward the specific ethnic group of the cradled individual can interfere with the left preference in the cradling woman. The present study corroborates our suggestion that the left-cradling bias might be considered as a natural index of a positive socio-communicative relationship between the cradling and cradled individuals. On the contrary, the right-cradling bias might be considered as a cue of the presence of affective dysfunctions in the relationship.

An examination of the leftward cradling bias among typically developing adults high on autistic traits

The leftward cradling bias is the tendency to cradle infants on the left side of the body and it has been linked with hemispheric asymmetry for emotional processing. This study examines this phenomenon using a real-size infant doll in typically developing adults who score high in the Reading the Mind in the Eyes, the Autistic Spectrum Quotient and the Empathy Quotient, measures that assess autistic traits among typically developing individuals. Results revealed that this group showed a reduced tendency to cradle on the left compared to participants who score within the normal range on the above measurements. This study provides further support for the justification of the leftward cradling bias upon brain lateralization on emotional processing. Study limitations and suggestions for future research are discussed.

Handedness as a major determinant of functional cradling bias

Cradling is an interactive activity, involving a manual component that is very often an integral part of cradling. Cradling, while doing something else with the free hand, is referred to here as functional cradling. This study examined the relationship between a person's handedness and what arm he or she prefers to use when functionally cradling a baby doll that resembles a newborn infant. A total of 765 participants took part in the experiment, 403 women and 362 men, between the ages of 4 and 86 years. Left- and mixed-handers were actively recruited. The sample consisted of 64.3% right-handed, 24.7% mixed-handed, and 11.0% left-handed participants. The results showed a clear tendency for participants to cradle in their non-dominant arm (p < .001). Furthermore, this tendency increased with age and it was present in both sexes, although significantly stronger in women than in men. On the other hand, experience with young children through younger siblings and/or being a parent did not increase the likelihood to cradle in the non-dominant arm. It is concluded that humans have a clear functional cradling preference for the non-dominant arm because this enables the dominant arm to engage in other tasks. This might also explain why previous studies have reported a universal left cradling bias because a right-handed majority (intuitively) keeps the dominant hand free when cradling.

Maternal cradling and infant nipple preferences in rhesus monkeys (Macaca mulatta)

This study investigated lateral biases in nipple preferences, maternal cradling, carrying, and retrieval in 41 rhesus macaque (Macaca mulatta) mother-infant dyads living in two captive social groups. Observations were made during the first 6 weeks of infant life using a combination of scan sampling and ad-libitum sampling techniques. Infants exhibited a significant left-nipple preference in the first weeks of life but the bias decreased with infant age. Mothers showed a left-arm bias in carrying their infants but no significant lateral bias in cradling or retrieval. Our results suggest that the left-side cradling bias reported in studies of humans and some other primates reflects a bias in the infant's nipple preference rather than in maternal behavior. The infants' preference for the left nipple is consistent with both Salk's (1960) heartbeat hypothesis and with more recent hypotheses linking this lateral bias with brain asymmetry and hemispheric specialization for mother-infant communication.

Lateral cradling preferences in children

Lateral preferences for cradling a doll and for holding a package were investigated among children from 2- to 6-yr-old. Results showed a preference for holding a baby on the left side of the body in children as young as 3 yr. old. The data favour the hypothesis of an early emergence of this pattern of behavior in the human ontogenesis.

A child-holding thought experiment: students prefer to imaging holding an infant on the left side of the body

The tendency of women to prefer to hold infants on the left side of the body has been confirmed by several methods: surveys of works of art and of photographs, field observations, and experimental methods. The present study developed a new method to examine the patterns of child-holding, that is, the child-holding thought experiment. 2287 female and 1268 male undergraduates were instructed to imaging nursing or feeding a baby. Then, they were asked on which side of the body they imagined holding the baby. Seventy-two percent of the women and 65% of the men reported imaging holding a baby on the left side of the body. This preference for the left side was noted, irrespective of handedness. These results indicate that both women and men who have never fed their own babies prefer to imaging holding a baby on the left side of the body. Moreover, that the magnitude of this preference was significantly stronger for the women adds to the evidence of a gender-dependent expression for lateral preferences in holding a baby.