Human and chimpanzee face recognition in chimpanzees (Pan troglodytes): Role of exposure and impact on categorical perception.

The respective influences of exposure and inborn neural networks on conspecific and nonconspecific face processing remain unclear. Although the importance of exposure in the development of object and face recognition in general is well documented, studies explicitly comparing face recognition across species showed a species-specific effect. For instance, laboratory monkeys exposed daily to human faces were better at discriminating monkeys than humans, suggesting that the role of exposure may not be the only factor affecting cross-species recognition. In the present study, the authors investigated conspecific and nonconspecific face recognition in chimpanzees (Pan troglodytes) from 2 primate centers that provided different exposure to chimpanzee and human faces. The authors showed that the chimpanzees from the center providing more exposure to human faces than to chimpanzee faces were better at discriminating human faces than they were at discriminating chimpanzee faces. The chimpanzees from the other center did not show the same effect. A computational simulation was developed to evaluate the average similarities among human pictures and among chimpanzee pictures. Both categories were comparable. Chimpanzees' scores were significantly correlated with the similarity coefficients. Overall, the results show that exposure is a critical determinant in conspecific and nonconspecific face recognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rhesus monkeys (Macaca mulatta) lack expertise in face processing.

Faces are salient stimuli for primates that rely predominantly on visual cues for recognizing conspecifics and maintaining social relationships. While previous studies have shown similar face discrimination processes in chimpanzees and humans, data from monkeys are unclear. Therefore, three studies examined face processing in rhesus monkeys using the face inversion effect, a fractured face task, and an individual recognition task. Unlike chimpanzees and humans, the monkeys showed a general face inversion effect reflected by significantly better performance on upright compared to inverted faces (conspecifics, human and chimpanzees faces) regardless of the subjects' expertise with those categories. Fracturing faces alters first- and second-order configural manipulations whereas previous studies in chimpanzees showed selective deficits for second-order configural manipulations. Finally, when required to individuate conspecific's faces, i.e., matching two different photographs of the same conspecific, monkeys showed poor discrimination and repeated training. These results support evolutionary differences between rhesus monkeys and Hominoids in the importance of configural cues and their ability to individuate conspecifics' faces, suggesting a lack of face expertise in rhesus monkeys. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Are faces of different species perceived categorically by human observers?

What are the species boundaries of face processing? Using a face-feature morphing algorithm, image series intermediate between human, monkey (macaque), and bovine faces were constructed. Forced-choice judgement of these images showed sharply bounded categories for upright face images of each species. These predicted the perceptual discrimination boundaries for upright monkey-cow and cow-human images, but not human-monkey images. Species categories were also well-judged for inverted face images, but these did not give sharpened discrimination (categorical perception) at the category boundaries. While categorical species judgements are made reliably, only the distinction between primate faces and cow faces appears to be categorically perceived, and only in upright faces. One inference is that humans may judge monkey faces in terms of human characteristics, albeit distinctive ones.     

Inversion effect for faces in split-brain monkeys

Inverting facial stimuli disrupts recognition in human subjects more severely than does inversion of other objects normally seen upright. Furthermore, this disruption affects mechanisms in the right hemisphere, which is the hemisphere preeminent for face processing, more than mechanisms in the left. To determine the extent of these effects in monkeys we retrained each hemisphere of 20 split-brain rhesus monkeys on eight upright facial discriminations they had previously learned. As a group, the monkeys again performed better with the right hemisphere than with the left in remembering these problems, confirming the right hemispheric advantage previously found. As soon as a particular discrimination was relearned to criterion with one hemisphere, the same discrimination was presented inverted. The monkeys learned the inverted facial discriminations with each hemisphere but as a group no longer showed a right hemispheric advantage. Thus, the monkeys, like people, show a greater inversion effect for faces with the right hemisphere than with the left. This result indicates that monkeys normally process faces configurally using holistic mechanisms in the right hemisphere but, when required by the nature of the stimuli, can utilize piecemeal processing of specific features with either hemisphere.     

Evidence of human-like, holistic face processing in spider monkeys (Ateles geoffroyi).

Human subjects build mental representations of facial identity that are “holistic.” This has been clearly demonstrated with the composite effect where the representation of a whole face interferes with the recognition of features. Very few studies have sought evidence of holistic representations being built by nonhumans. This study tested captive, black-handed spider monkeys (N = 2) on a standard composite task, comparable to those run previously on human subjects. In Experiment 1, the monkeys were tested with the faces of conspecifics (Ateles geoffroyi), humans (Homo sapiens), and domestic sheep (Ovis aries) together with stick objects. The results of Experiment 1 revealed that both conspecific and human faces were processed holistically. The subsequent test (Experiment 2) confirmed that, for both subjects, the face composite effect was contingent on upright orientation. A direct comparison with available human data demonstrates a level of similarity, strongly suggestive of cognitive homology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sexual dimorphism in facial shapes and their discrimination in Japanese monkeys (Macaca fuscata).

The authors examined the ability of Japanese monkeys (Macaca fuscata) to discriminate between sexes based on facial features. The shape and position of facial features (facial morphology) were measured to quantify the differences between sexes. The distance between the chin and nose was longer in males than females, and the outline of the face around the upper jaw and upper face differed between sexes. Using operant conditioning, 2 monkeys succeeded in discriminating sex based on facial pictures. Furthermore, they successfully generalized the discrimination to novel pictures of faces. Tests with morphed pictures of faces revealed that the monkeys used facial morphology to discriminate between males and females. Our results suggest that Japanese monkeys have sexual dimorphism in facial shape and they can use the morphological differences to discriminate conspecific sex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Monkeys and mug shots: Cues used by rhesus monkeys (Macaca mulatta) to recognize a human face.

Investigated the cues rhesus monkeys (Macaca mulatta) use to recognize a familiar human face. To manipulate facial cues, schematic faces were constructed with Identi-Kit materials derived from mug shots. The monkeys (N?=?4) spontaneously classed Identi-Kit stimuli as faces on initial presentations. The monkeys then learned to distinguish one Identi-Kit face, the standard, from others. Panel presses indicated recognition of the standard eye. Eye movement recordings revealed that the monkeys predominantly fixated on the eyes of the standard face. When the standard face was transformed by removing, altering, or reorienting its features, only alterations of eyes or brows lowered recognition; removal of eyes, brows, nose, or lips did not. Responses to rotated, inverted, and scrambled versions of the standard face varied but generally disrupted recognition. It is concluded that features and configuration were used to recognize the human face. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Face detection in peripheral vision: do faces pop out?

We examined whether faces can produce a 'pop-out' effect in visual search tasks. In the first experiment, subjects' eye movements and search latencies were measured while they viewed a display containing a target face amidst distractors. Targets were upright or inverted faces presented with seven others of the opposite polarity as an 'around-the-clock' display. Face images were either photographic or 'feature only', with the outline removed. Naive subjects were poor at locating an upright face from an array of inverted faces, but performance improved with practice. In the second experiment, we investigated systematically how training improved performance. Prior to testing, subjects were practised on locating either upright or inverted faces. All subjects benefited from training. Subjects practised on upright faces were faster and more accurate at locating upright target faces than inverted. Subjects practised on inverted faces showed no difference between upright and inverted targets. In the third experiment, faces with 'jumbled' features were used as distractors, and this resulted in the same pattern of findings. We conclude that there is no direct rapid 'pop-out' effect for faces. However, the findings demonstrate that, in peripheral vision, upright faces show a processing advantage over inverted faces.     

Local and relational aspects of face distinctiveness

Distinctiveness contributes strongly to the recognition and rejection of faces in memory tasks. In four experiments we examine the role played by local and relational information in the distinctiveness of upright and inverted faces. In all experiments subjects saw one of three versions of a face: original faces, which had been rated as average in distinctiveness in a previous study (Hancock, Burton, & Bruce, 1996), a more distinctive version in which local features had been changed (D-local), and a more distinctive version in which relational features had been changed (D-rel). An increase in distinctiveness was found for D-local and D-rel faces in Experiment 1 (complete faces) and 3 and 4 (face internals only) when the faces had to be rated in upright presentation, but the distinctiveness of the D-rel faces was reduced much more than that of the D-local versions when the ratings were given to the faces presented upside-down (Experiments 1 and 3). Recognition performance showed a similar pattern: presented upright, both D-local and D-rel revealed higher performance compared to the originals, but in upside-down presentation the D-local versions showed a much stronger distinctiveness advantage. When only internal features of faces were used (Experiments 3 and 4), the D-rel faces lost their advantage over the Original versions in inverted presentation. The results suggest that at least two dimensions of facial information contribute to a face's apparent distinctiveness, but that these sources of information are differentially affected by turning the face upside-down. These findings are in accordance with a face processing model in which face inversion effects occur because a specific type of information processing is disrupted, rather than because of a general disruption of performance.     

Encoding Operations and Recognition Memory for Faces.

Two experiments examined the effects of encoding operations on forced-choice recognition memory for upright and inverted photographs of faces. In Experiment 1, with distractors closely matched to targets, performance was better on upright than on inverted faces, but was unaffected by whether subjects judged faces for distinctive features, distinctive traits or distinctive expressions. In Experiment 2, where distractors were either absent or weakly matched to distractors, accuracy was again higher on upright than on inverted faces, and was similar for the three encoding operations on upright faces. In contrast, it was poorer for distinctive expression judgments than for distinctive feature or for distinctive trait judgments on inverted faces. These results support Winograd's (1981) claim that distinctive feature and distinctive trait judgments both lead to the isolation of distinctive features. However, it was argued that distinctive expression judgments led to configural processing that was disrupted by inversion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

What facial part is important for Japanese monkeys (Macaca fuscata) in recognition of smiling and sad faces of humans (Homo sapiens)?

Four Japanese monkeys (Macaca fuscata) and 17 humans (Homo sapiens) performed an odd-item visual search task of a variety of photos of human facial expressions. The target was either a genuine smiling face or a sad face of a female. The distracters were the following artificial images produced by a computerized image processing system: (a) a neutral face made by averaging the 2 targets or (b) faces with smiling or sad eyebrows, eyes, cheeks, or mouth on the neutral face. The search reaction time of both species was the longest when they had to find the smiling target among the distracters having the smiling cheeks. In searching for the sad target, however, the reaction time of humans was the longest when the distracters had sad eyebrows or sad cheeks, whereas the longest reaction time for monkeys was when the distracters had sad cheeks. These results indicate that monkeys search smiling human faces as humans do, but monkeys do not use eyebrows as a cue to search sad human faces. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hand preferences in unimanual and coordinated-bimanual tasks by tufted capuchin monkeys (Cebus apella).

Hand preferences in 26 capuchin monkeys (Cebus apella) were examined in 2 reaching-for-food tasks under 2 postural conditions. In the 1st task (unimanual), monkeys were required to reach for food from both a quadrupedal and an upright posture. A right-hand bias was found for the upright but not for the quadrupedal condition. In the 2nd task (coordinated bimanual), monkeys were required to extract the food from a hanging Plexiglas tube from both a crouched and an upright posture. A right-hand bias was found for both conditions. A significant increase in right-hand use was noted from the unimanual, quadrupedal, reaching task to the coordinated-bimanual task, with females exhibiting a greater right-hand preference than males. In addition, a significant effect of task complexity on strength in laterality was found. Results are discussed in the context of recent theories on primate laterality. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual list memory in capuchin monkeys (Cebus apella).

Memory of 3 capuchin monkeys, Cebus apella, was tested with lists of 4 travel-slide pictures and different retention intervals. They touched different areas of a video monitor to indicate whether a test picture was in a list. At short retention intervals (0 s, 1 s, 2 s), memory was good for the last list items (recency effect). At a 10-s retention interval, memory improved for 1st list items (primacy effect). At long retention intervals (20 s and 30 s), primacy effects were strong and recency effects had dissipated. The pattern of retention-interval changes was similar to rhesus monkeys, humans, and pigeons. The time course of recency dissipation was similar to rhesus monkeys. The capuchin's superior tool-use ability was discussed in relation to whether it reflects a superior general cognitive ability, such as memory. In terms of visual memory, capuchin monkeys were not shown to be superior to rhesus monkeys. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of cross-modal recognition in infant pigtail monkeys (Macaca nemestrina).

Examined the development of cross-modal recognition in 48 infant pigtail monkeys in 2 studies by using an adaptation of the visual preference technique. Ss were first familiarized orally with pacifiers of 1 of 2 shapes and were then tested on corresponding visual stimuli. In a cross-sectional experiment (Exp I), Ss under 200 days postconception at test (approximately 4 postnatal weeks) showed a visual preference for the orally familiar stimuli, which provided evidence for cross-modal recognition. Ss over 200 days postconception at test showed a visual preference for 1 of the test stimuli, which made their data uninterpretable with respect to cross-modal abilities. In a longitudinal experiment (Exp II), Ss were tested once when they were younger than 200 days postconception and once when they were older. When young, they showed a visual preference for the orally familiar stimuli. When older, they showed a visual preference for the same test stimuli found for the cross-sectional Ss. Results are discussed relative to human infant cross-modal data obtained by similar procedures. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Why faces are and are not special: An effect of expertise.

Conducted 4 experiments to demonstrate that faces are not unique with regard to vulnerability to inversion (i.e., impairment of recognition memory with inverted presentation) and to isolate the source of the inversion effect. In Exp I, with 16 undergraduates, use of stimuli (landscapes) in which spatial relations among elements are potentially important distinguishing features was shown not to guarantee a large inversion effect. Exps II and III (with 64 undergraduates, 16 dog experts [aged 29–58 yrs], and 16 dog experts [aged 42–77 yrs]) showed that for dog experts sufficiently knowledgeable to individuate dogs of the same breed, memory for photographs of dogs of that breed was as disrupted by inversion as face recognition. Exp IV, with 19 undergraduates, indicated that the effect of orientation on memory for faces did not depend on inability to identify single features of these stimuli upside down. Findings are consistent with the view that experts represent items in memory in terms of distinguishing features of a different kind than do novices. Speculations as to the type of feature used and neuropsychological and developmental implications of this accomplishment are offered. (42 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Face–name interference.

Investigated interference effects between the processing of simultaneously presented photographs of faces of familiar people and printed names of familiar people in 5 experiments each with 12 adult Ss. Results show that printed names interfered with identifying faces, whereas faces did not interfere with saying printed names. In contrast, faces interfered more with name categorization than names interfered with face categorization. It is suggested that despite a priori reasons as to why faces might be thought to possess functional properties different from those of other visual objects, the observed effects are comparable to those found in object–word interference studies, with photographs of faces behaving like pictures of objects and printed people's names behaving like printed names of objects. In face naming tasks, the presence of related names produced more interference than did the presence of unrelated names. This effect was examined in greater detail in Exp III, where it was found that the effect arose when the face and the name belonged to people of similar appearance. An effect of common category membership was not found in Exp III. Exp V, however, showed that names of people highly associated with the person whose face was presented also produced more interference than did names of unrelated people. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex, Age, and Training Modulate Spatial Memory in the Rhesus Monkey (Macaca mulatta).

The authors tested 90 rhesus monkeys (Macaca mulatta) on a task of spatial memory, the spatial Delayed Recognition Span Test. The results showed that performance declined significantly with age, males had greater scores than females, and the rate of apparent decline with age was greater in males than in females. Both working and reference memory declined with age, but only working memory showed sex differences. The authors compared these data with that of 22 monkeys who were trained on a simpler version of the task before formal testing. Training had no effect on males but dramatically improved working memory in young females. The results confirm a male advantage in spatial working memory at a young age and confirm a greater decline with age in males than in females. It is important to note that prior training completely reverses the deficits of young females. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Memory for picture fragments in monkeys and humans.

Utilized a delayed matching-to-sample procedure to study recognition memory for picture fragments in 33 undergraduates and 3 squirrel monkeys (Saimiri sciureus). Three types of masks varied in the part of the picture they covered, either the center, the periphery, or randomly selected small portions of the picture (noise mask). In Exp I, Ss saw whole sample pictures and had to respond to fragments as comparison pictures. In Exp II, fragments were presented as samples and whole pictures as comparison stimuli. In Exp III, both the samples and comparisons were picture fragments. Recognition accuracy improved in both monkeys and humans as the percentage of the picture exposed increased, and accuracy was lowest with a central mask, intermediate with a noise mask, and highest with a peripheral mask. Data may be used to argue for similar content of visual memories in monkeys and humans. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Categorical perception of face identity in noise isolates configural processing.

Neuropsychological evidence suggests that face recognition based on configural (holistic) information can occur in isolation from recognition based on local feature cues. The present study shows that configural processing can be isolated experimentally in normal subjects. A phenomenon is reported that exists only for upright whole faces, namely categorical perception (CP) of face identity in noise. Three discrimination tasks (ABX, better likeness, and similarity ratings) were used to test for perceptual distortion across the category boundary predicted from binary classification of face morphs. Noise was added such that any single local region provided unreliable cues to identity. Under these conditions, CP was found for upright faces but not for inverted faces or single features, even with more than 10,000 trials. The CP-in-noise signature phenomenon was then used to show that configural processing survives image plane rotations of 45°–90°. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

What meaning means for same and different: Analogical reasoning in humans (Homo sapiens), chimpanzees (Pan troglodytes), and rhesus monkeys (Macaca mulatta).

Thus far, language- and token-trained apes (e.g., D. Premack, 1976; R. K. R. Thompson, D. L. Oden, & S. T. Boysen, 1997) have provided the best evidence that nonhuman animals can solve, complete, and construct analogies, thus implicating symbolic representation as the mechanism enabling the phenomenon. In this study, the authors examined the role of stimulus meaning in the analogical reasoning abilities of three different primate species. Humans (Homo sapiens), chimpanzees (Pan troglodytes), and rhesus monkeys (Macaca mulatta) completed the same relational matching-to-sample (RMTS) tasks with both meaningful and nonmeaningful stimuli. This discrimination of relations-between-relations serves as the basis for analogical reasoning. Meaningfulness facilitated the acquisition of analogical matching for human participants, whereas individual differences among the chimpanzees suggest that meaning can either enable or hinder their ability to complete analogies. Rhesus monkeys did not succeed in the RMTS task regardless of stimulus meaning, suggesting that their ability to reason analogically, if present at all, may be dependent on a dimension other than the representational value of stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)