PSYCHOLOGY:

Given that human infants (and the infants of many other animal species) are entirely dependent on their parents and/or other caregivers for survival, there's a strong evolutionary advantage to infants possessing the ability to attract feeding and other caregiving behaviors. In many species, neuroscience and psychology experiments have shown that certain infant facial features (e.g. rounded cheeks and large eyes) trigger reward systems in the adult brain, elicit positive behaviors among adults, and direct adult attention away from other stimuli.

Current hypotheses suggest that adults of a given species should exhibit caregiving behavior towards all infants of their species. On the other hand, much research has shown that people are less sensitive to facial features of other races, unless they have a significant level of exposure to differing races.

John Hodsoll (Queen Mary University, United Kingdom) and coworkers have shown that preferential adult attention to infant facial features is affected by the race of the infant relative to that of the adult, suggesting an influence of experience and environment. Their research says nothing about whether practical caregiving behaviors are influenced by experience and environment.

Experimental setup.

The scientists studied 40 female undergraduate students, born in the United Kingdom, and enrolled at the University of Birmingham. Half of them were white and the other half were of south Asian decent.

They were on average 20 years old, all had normal (or corrected to normal) vision, and all were right handed. Each student received course credit for participation in the experiments.

The participants first viewed a fixation cross on a computer screen for 500 milliseconds. They then viewed two pictures simultaneously displayed on a computer screen for 200 milliseconds, one of an infant and one of an adult, either white or south Asian decent.

Both faces were grayscale, the same race, and of similar expression (neutral), brightness, sharpness, and contrast. Fifty milliseconds after the pictures disappeared from the computer screen, a triangle appeared on the computer screen for 100 milliseconds.

This triangle appeared in the center of the former location of one of the two faces. This was followed by a blank screen.

The participants recorded whether the triangle had been pointing up or down, by pressing one of two buttons on the computer keyboard. If the triangle appeared, for example, on the former location of the infant face, and the participant was focusing on the infant face, response should be faster than if the participant was focusing on the adult face.

Each participant first completed 32 practice trials. They then completed 128 random trials, divided evenly between the race of the images and the relative facial (adult or infant) positions and direction (up or down) of the triangle on the computer screen.

The response time was recorded for each trial by each participant. The hypothesis was that response time may vary depending on the race of the participant in relation to the race of the images.

Racial bias in attention.

The participants' reaction times were slower by 9 milliseconds when the triangle appeared in the same location of the adult (524 milliseconds) relative to the infant (513 milliseconds) face. Yes, this is a small difference (2%), but it was statistically significant, i.e. the difference is real.

Most importantly, the infant-to-adult preference was stronger (by about 10 or 15 milliseconds i.e. 2-3%), when the race of the participant matched that of the faces on the computer screen. This trend held whether the participants were of white or south Asian decent.

Overall evaluation.

There are clearly racial biases in adult attention to infant facial expressions. Why might this be the case?

One possible explanation is that racial features such as skin pigmentation are picked up faster than infant facial features. Another possibly interlinked explanation is that the participants were not as adept at distinguising the faces of races different from their own (either infant or adult).

This research does not demonstrate that racial biases influence practical parental care of infants. In this context, the scientists' preliminary results in further experiments, which suggest that the participants rated infants of other races as more pleasing than their own race, is particularly interesting.

However, those latter results are still preliminary. Furthermore, it's easy for me to envision racial biases influencing such results from multiple directions.

For example, the participants may desire to not appear racist, and therefore provide enhanced attractiveness ratings to infants of other races. Participant anonymity during testing may help settle such concerns, when futher experiments are carried out.

NOTE: The scientists' research was funded by the Biotechnology and Biological Sciences Research Council.

for more information:
Hodsoll, J., Quinn, K. A., & Hodsoll, S. (2010). Attentional Prioritization of Infant Faces Is Limited to Own-Race Infants PLoS ONE, 5 (9) : 10.1371/journal.pone.0012509