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a. Human vs Macaques
In this experiment, I assessed categorization ability of M. fascicularis to discriminate monkeys from humans using facial features. Both primates possess
distinctive physical features, notably different shape of face and the presence of hair in the monkeys face which is absent from human. These distinctions would
allow us to safely infer the discriminative ability on the different conceptual class of human and monkey. For monkey category, I used photos of both sexes of three
species of macaques, those were M. fascicularis, M. mulatta and M. fuscata. For human category, I used female and male photos. Some of the female heads were
covered by scarf. Nevertheless, all pictures showed the whole face. For training phase, sample and matching stimuli were the same and
monkeys stimuli were always M. fascicularis see Figure 2b and 2d. For practical reason, I used 90 correct rate as threshold to infer subjects competence
in discriminating human from monkey categories. Furthermore, to make sure they have achieved this ability, they have to show it in three successive sessions.
To test if a subject could apply the learned concept of human and monkeys to new individuals, I changed the pictures of matching stimulus with different
individuals that belonged to the same category as the sample stimuli eg. Figure 2c , 2e, 2g; for example, if the sample stimulus is monkey b then the matching
stimulus is monkey d. The subject should compare the novel matching stimulus to the available distractor. If the subject associate the sample and the different-
picture of matching stimuli, I may infer that they put those two pictures into one class that dichotomically differs from the class of distractor. This would evidenced
they transfer the human and monkey concepts to novel stimuli. This would prove their categorization ability. For practical reason, the test sessions consisted of
baseline and test trials in certain proportion. In the baseline trials, the stimuli is the same as in training trials so this would provide a reference to compare the test
trials. The stimulus photos give subjects various informations about color and
shape of each species. Thus, I expected that subjects used informations from detailed physical properties of sample and matching stimuli to perform basic level
11 of categorization. To test whether the subjects has levels of abstraction, I extended
the experiment to see whether the subjects would still have the ability to identify objects if the informations on the physical properties of the stimuli were reduced.
For this reason, I deviced extended experiments that stripped off certain visual information from the stimuli. First, I took color off the photos and presented it in
black and white. In the next step, I tried to test whether size of the stimuli could affect the performance of the subjects in categorizing humans differently from
monkeys. I thought that altering the size of the photos would also perspectively change the shape of the figures. I reduced the size of the stimuli to one quarter of
the original and showed it to monkeys. In this case, I tested them using pairs of photos of colored human and M. fascicularis. I continued the test by giving the
subjects the blurred, black and white, original size photos of human and macaques. These photo manipulations aimed to test whether the subjects could
categorize human differently from monkeys though the stimuli lack informations about color and shape. In my last attempt to ascertain whether the subjects could
categorize human differently from macaques, I reduced the size of the black and white, blurred photos of human and monkeys to one quarter of the original size.
The complete and modified physical properties of the photo stimulate the varied amount of information perceived on the objects. Thus, by comparing subjects
responds to the stimuli, I may interpret their level of categorization. In total, I used 82 photos as the stimuli for the test.
b. Macaca fascicularis vs Other Macaques
Kategori