Mondloch et al (1999) tested twelve-week old human babies, six-week-old human babies, and newborn human babies using a standardized methodology based upon the Teller acuity card procedure. This procedure involves an observer who is unaware of the precise stimuli that are presented throughout the course of each trial making a decision regarding whether infants are capable of seeing the stimulus based upon their behavior. However, in this case, the observers decided whether the infant preferred one of two stimuli displayed on pairs of cards.
One of the pairs consisted of a card displaying an image that roughly resembled a human face and a card that displayed the same image inverted. One of the pairs consisted of two cards with images of faces distorted in different ways. The final pair involved a card displaying an image that roughly resembled a human face and a card displaying the same image with its contrast reversed.
The results were that the majority of the newborn babies showed a preference for the non-inverted face when they were presented with the first pair of cards, the second distorted image when they were presented with the second pair of cards, and neither image when they were presented with the third pair of cards. The majority of the six-week-old babies showed no preference for either image when they were presented with the first pair of cards, demonstrated a preference for the first distorted when they were presented with the second pair of cards, and showed no preference for either image when they were presented with the third pair of cards. The twelve-week-old babies showed no preference for either image when they were presented with the first pair of cards, demonstrated a preference for the first distorted image when they were presented with the second pair of cards, and the face with its contrast reversed for the final pair of cards (Mondloch et al, 1999).
In the study by Sugita, infant monkeys were not given any exposure to faces for a period of between six and twenty-four months. They were then showed images of monkey and human faces and tested to see if they had a preference for these images over other images. They were observed to prefer both monkey and human faces to the other images. The monkeys were then exposed to monkey and human faces for a period of a month. After this period, they displayed a preference for money faces but not those of other species (Sugita, 2007).
Mondloch et al’s (1999) paper is directly related to face perception, as it provides an indication of how human beings at various different stages of their development perceive faces with regards to differentiation based upon a range of different factors. Sugita’s (2007) study is also related to this area. However, it is different in that it focuses upon face perception at different levels of exposure to faces as opposed to the age of the perceiver. It expands research into this area by using animal participants to conduct an experiment that would be considered to be unethical if it was carried out on human subjects.
The human and animal children are similar in that they were both discovered to show an innate preference for faces over other images. However, the monkeys differed from the human babies in that once they had been exposed to monkey faces, they showed a preference for them over other faces. Further research could be carried out in order to see if human babies prefer human faces over those of other species once they get past a certain level of development.
The methodologies of these two experiments differ in that steps were taken to ensure that the monkeys did not encounter any faces for a prolonged period, whereas the human babies were raised normally. Had the human babies been isolated in this manner, it could have damaged their development. However, it is arguable that their previous exposure to faces might have influenced the result, especially seeing as some babies might have come into contact with a greater variety of faces than others.
The other major different with regards to the methods was the techniques that were utilized in order to judge whether the participants were attentive to a particular image. In Mondloch et al’s’s study, as previously stated, a variant of the Teller acuity card procedure was used, whereas in Sugita’s (2007) study, the amount of time spent looking at each image was measured. It is arguable that the latter methodology is less subjective than the former, as it does not rely upon human interpretation of cues from the participant, meaning that it is not as prone to researcher bias.
Mondloch et al’s study has an advantage over Sugita’s (2007) study in that the results can be generalized to other human babies, whereas is possible that the findings of Sugita’s (2007) study might only apply to monkeys and not to human beings. Although the two species are closely related, they are not necessarily identical in terms of their development of face perception. This means that Mondloch et al’s (1999) experiment provides more of an accurate insight into human development.
However, the Sugita’s research has uncovered background information on face perception in other primates. Seeing as human beings and monkeys are thought to have developed from a common ancestor, this can be used in conjunction with research on human participants in order to shed light upon the extent to which the two species are similar in this respect. The findings can also be used as the basis for future studies on human participants.
Several questions are left unexplored by this research. Although it has been concluded that monkeys discriminate faces before they have been exposed to them, there is no conclusive evidence that the same is true of humans. Similarly, there is no evidence that other species discriminate based upon the characteristics that Mondloch et al’s (1999) study found human babies to discriminate based on. Therefore, more research could be conducted in order to expand the base of knowledge concerning this area.
- Mondloch, C., Lewis, T., Budreau, R., Muarer, D., Dannemiller, J., Stephens, B. & Kleiner-Gathercoal, K. (1999). Face Perception During Early Infancy. Psychological Science, 10 (5), 419-422. Retrieved from http://cseweb.ucsd.edu/~gary/cs200/w04/papers/Mondloch_et_al.Facecards.pdf
- Sugita, Y. (2007). Face perception in monkeys reared with no exposure to faces. PNAS, 105 (1). Retrieved from http://www.pnas.org/content/105/1/394.full