Article: Sugita, Y. “Face Perception in Monkeys Reared with No Exposure to Faces.” PNAS 105, no. 1 (2008): 394–98. DOI: 10.1073/pnas.0706079105

Assignment: Read the assigned article carefully and think about it, then provide short answers to the questions below. Be clear and concise—points will be taken off for unnecessary words.

Notes: This is a hard assignment. Two videos that might also be helpful are:

• Nancy’s Brain Talks: How do you ask a preverbal infant what she can see?
• Nancy’s Brain Talks: What is the role of experience in the development of face recognition?

1. The above results are from a preferential looking task in monkeys. To conduct a preferential looking task, two objects or pictures are placed side by side within the subject’s field of view. The amount of time spent looking at each object/picture is measured for a fixed period. The above plots are the results of the preferential looking test described in Sugita 2008.  Describe the results and attempt to explain their importance.

These results prefer the time looking at one stimulus when presented with two stimulus. The monkeys are more interested in and recognize better the stimulus they look at for longer. In the control, the monkeys have no preference between objects and humans, but prefer looking at monkeys over both. This suggests that monkeys normally can’t recognize human faces. The experimental results suggest for all three deprivation periods, the monkeys equally prefer human faces and monkey faces over objects. They are just as good at recognizing human faces as monkey faces, despite having no experience with any kind of face. This also suggest that experience is not necessary to develop face recognition ability.

Does preferential looking really imply recognition

2. A visual paired-comparison procedure (VPC) uses habituation to determine if subjects can discriminate between pairs of stimuli in the same class.* The above plots are from Sugita 2008 and depict the results of a VPC test in face-deprived (A) and typically developed (B) monkeys. What are the key results? Explain their implications.

VPC more directly tests for recognition by testing whether the subject considers a stimulus novel or not. In the control, there is no difference between new and old for humans, but there is a strong difference for monkeys. With face deprivation, the monkeys are able to recognize novel monkey and human faces.

3. Inspired by Sugita, you decide to test whether you can find an FFA in young monkeys using fMRI. To do so, you design two different experiments described below. For each experiment first state your hypothesis based on the Sugita paper, and then your specific predictions for the following specific findings: (i) the response you might expect to see to faces compared to objects in a region of the ventral temporal cortex (approximately where you would find the FFA in adults); and (ii) the rationale behind your predictions. Feel free to use words or make simple plots. Use only what you know from class (especially the snake homework) and the Sugita paper.

a) Experiment 1: A blocked design with black and white images of faces, bodies, objects, and scenes. Each image is presented for 500 ms and each block is 18 seconds long.

I would expect to see increased activation in the VTC for face stimuli compared to the other stimulus classes. However this is only for monkey faces, unless there has been face deprivation. The Sugita paper implies that monkeys don’t have the specialized ability to recognize human faces, so the FFA would consider a human face to be a normal object.`

b) Experiment 2: Similar to the protocol established by Sugita et al., infant monkeys are face-deprived for 6, 12, and 24 months. Similar to Experiment 1, the paradigm is a blocked design with black and white images of faces, objects, bodies and scenes. Each image is presented for 500 ms, each block is 18 seconds long, and monkeys are passively viewing the stimuli. Monkeys are scanned twice—once at the end of the face deprivation period (t = 0) and once 6 months later (t = 6).

• If this description of VPC is unclear, a more thorough explanation can be found here: Nancy’s Brain Talks: What is the role of experience in the development of face recognition?

At t=0 the monkeys’ FFA would activate for all kinds of faces. At t = 6, it would only activate for the kind of faces that they have seen in their environment.