Remember those endearing photos of grey-lag geese following Austrian psychologist Konrad Lorenz (1903-1989) around in the firm belief that he was their mother? The geese imprinted on Lorenz supposedly because he was the first moving object they spotted. Funny story. Behavioral psychologist Gilbert Gottlieb (1929-2006) found that ducklings didn't imprint on movement as Lorenz had thought. They actually followed the voice, whether it moved or not. Even more astounding-Gottlieb's duckies responded to their own species' quack even if they did not first hear it from an adult. Years of experimentation ensued and long story short, the ducks start quacking in the egg a couple of days before they hatch. If Gottlieb muted them before they started to quack, they would imprint as easily on a chicken's call as they would on their own duck species. Deprived of hearing their own in-shell quacking, the ducklings developed a hearing deficit because the ability to hear calls of a certain frequency depended on exposure to the sound of their own voices. What first seemed to be instinctive--baby ducks born to follow their mother--turned out to be a developmental system . The duckling starts quacking in the shell; the quacking promotes development of the auditory system; the duckling hatches, both sees and hears the mother duck and turns to it for protection.
Imprinted goslings
As he dug into this developmental system, Gottlieb discovered another feature: it did not necessarily develop in a fixed sequence. If he reared ducklings in a group and played them chicken songs, they imprinted on the chicken sounds even if they already could hear their own quacks. Raised alone, however, their developmental systems fixed only on their species call. What was it about group living that added plasticity to call imprinting? The experiments were many, but the results were clear. The imprinting system remained open to chicken (and other calls) only if the babies could touch one another or even a stuffed duckling. The original studies, which suggested a rather rigid developmental system turned out to have been skewed by the experimental design, which involved raising the duck babies in little duckie isolettes. Apparently, the stress of isolation interfered with brain development and rigidified the developmental possibilities for call imprinting.
Cute. But does this tell us anything about gender? Maybe. For starters, the human womb is a noisy place. Late term fetuses can and do respond to the mother's intestinal rumbles and heartbeat as well as to external voices and music. Newborns already prefer their mother's voice over that of a stranger. They already recognize the emotional content of their native language (compared to a foreign tongue). They even cry in a melody (if you can call a screaming infant melodious) that resembles the melody features of their native tongue. Even before birth then, the sound production system develops under the influence of specific experience. Many details remain to be clarified, but few scientists doubt that important changes in the nervous system--including the brain's cerebral cortex--result from all that prenatal noise; further input after birth continues to shape the neurological underpinnings that attune infants to the subtleties (emotional as well as syllabic) of the human voice, and ultimately to the shaping of their own sounds.
Still, there is even more going on than a relatively simple system circuit of sound-hearing development-vocalization-sound production. Remember how the ducklings needed tactile input? An interactive timing of vocal and emotional exchange also develops between human caregiver and infant. Both bring their own activities to the table, but the early months of holding and rocking and cradling serve to coordinate the two into a unit of give and take that mimics the timing of adult conversation. Furthermore, the degree of coordination seen at four months, predicts the level of security or anxiety an infant shows at one year.
OK. Gender. Let's focus on a finding that is oft exaggerated, but has some basis in fact. Girls start talking a month or two earlier than boys, and remain more advanced during the first 2-3 years in terms of vocabulary, sentence and paragraph production. The differences are small, i.e. there are many slow to talk girls and lots of very chatty boys, but when measured in a large population they are statistically significant. In one study conducted between the ages of 4 and 12 months, the two sexes started out with the same duration of babbling. However, babbling duration for the girls increased linearly, while that for the boys didn't change. At the same time, the mother's vocal responses to boys' babbles decreased, while maternal vocal responses to girls' babbling increased. We do not know why mothers respond differently to their sons and daughters, but I suspect the reasons are multiple. For example, psychologists Alan Fogel and Hui-Chin Hsu found that the structure of the mother son and mother daughter dyads differ at four months, with sons engaging in briefer periods of eye contact when held in their mother's arms. So the whole touch, talk, hold connect nexus may differ for adult-boy and adult-girl dyads, which could lead to different patterns of speech development.
We need to learn more about these early days of pre-speech noise making. And the proper framework for understanding patterns of production-including what circumstances make development less plastic (like the baby ducks raised in isolettes) and what leads to greater plasticity (touching and fuzzy feathers for the ducks), is a systems approach. Gender similarities and differences may emerge from the dynamic interplay of systems such as hearing, sound production and emotional attachment as they play out for girl and for boy infants and their caregivers. So the next time you hear "QUACK!!!", don't think about nature VERSUS nurture; think about how nurture rewires nature.
