Visual self-recognition in mirrors and live videos: Evidence for a developmental asynchrony

Three experiments (N = 123) investigated the development of live-video self-recognition using the traditional mark test. In Experiment 1, 24-, 30- and 36-month-old children saw a live video image of equal size and orientation as a control group saw in a mirror. The video version of the test was more difficult than the mirror version with only the oldest children's performance approaching ceiling. In Experiment 2, most 24-month-olds showed self-recognition when presented with a TV-set that featured a mirror in place of a screen. This finding does not substantiate the possibility that expectations about what appears on TV are responsible for the asynchrony. In Experiment 3, children were given a mark-test involving only their legs. Again, a video version was more difficult than previously reported performance with mirrors, suggesting that the impossibility of eye-contact in video cannot explain this developmental asynchrony. The findings suggest that self-recognition can be added to the growing list of contexts in which 2-year-olds display what has been called a “video deficit” [Anderson, D. R., & Pempek, T. A. (2005). Television and very young children. American Behavioral Scientist, 48, 505–532].     

Use of experimenter-given cues in visual co-orienting and in an object-choice task by a new world monkey species, cotton top tamarins (Saguinus oedipus)

Two methods assessed the use of experimenter-given directional cues by a New World monkey species, cotton top tamarins (Saguinus oedipus). Experiment 1 used cues to elicit visual co-orienting toward distal objects. Experiment 2 used cues to generate responses in an object-choice task. Although there were strong positive correlations between monkey pairs to co-orient, visual co-orienting with a human experimenter occurred at a low frequency to distal objects. Human hand pointing cues generated more visual co-orienting than did eye gaze to distal objects. Significant accurate choices of baited cups occurred with human point and tap cues and human look cues. Results highlight the importance of head and body orientation to induce shared attention in cotton top tamarins, both in a task that involved food getting and a task that did not.     

Variability in the early development of visual self-recognition

A study was conducted to evaluate the (1) developmental course and (2) the temporal sequencing of visual (mirror, photo) and verbal (personal pronoun use) measures of self-recognition as well as the ability to locate a toy from its mirror image in relation to the child's own mirror image. A microgenetic approach was adopted to assess 10 toddlers biweekly between 15 and 23 months of age and for comparison, a cross-section of children tested once across the same age range. Longitudinal data indicated that visual self-recognition emerged gradually and showed wide variability in expression prior to becoming stable, a finding masked in the cross-sectional data where performance appeared to improve abruptly. Both cross-sectional and longitudinal data confirmed that mirror self-recognition was the earliest precursor of the indices of self-recognition to emerge followed by the use of personal pronouns and photo identification. Implications for the emergence and integration of the self are discussed.     

The relationship between problem solving and inhibitory control: cotton-top tamarin (Saguinus oedipus) performance on a reversed contingency task

To explore the relationship between problem solving and inhibitory control, the authors present 4 experiments on cotton-top tamarins (Saguinus oedipus) using a reverse-reward contingency task. In Experiment 1, 1 group of tamarins was given a choice between a small and a large quantity of food. Whichever quantity the tamarins reached for first, they received the alternative. The tamarins consistently picked the larger quantity, thereby receiving the smaller. A 2nd group of tamarins was given the same task, except that if they reached for the larger quantity of food, they received nothing. The tamarins continued to pick the larger quantity, even though this resulted in no food. In addition, most of the tamarins continued to pick the larger quantity even when the food payoff for choosing the smaller quantity was increased (Experiment 2) or when the visual salience of the food was reduced (Experiment 3). Experiment 4 was based on the finding that chimpanzees (Pan troglodytes) that have been trained on the concept of number can solve the reversed contingency task if the food is replaced by Arabic numerals. With the help of a color association, and a higher cost incurred by picking the color associated with 3 food items, the tamarins learned to pick the color associated with 1 food item. These results are compared with those obtained from studies of other primate species, highlighting the importance of comparative studies of problem solving that use comparable methods.     

A transformation of self-discrimination response functions in accordance with the arbitrarily applicable relations of sameness, more than, and less than

In Experiment 1, 2 experimental subjects were given pretraining of nonarbitrary relations that brought their responses under the control of four contextual stimuli; same, opposite, more than, and less than. One control subject was not exposed to this pretraining. The 2 pretrained subjects and the 3rd nonpretrained subject then received training in six arbitrary relations, the following four relations being the most critical: same/A1-B1, same/A1-C1, less than/A1-B2, more than/A1-C2. All 3 subjects were then tested for seven derived relations, the following three relations being the most important: same/B1-C1, more than/B1-C2, less than/B1-B2. The 2 pretrained subjects, but not the nonpretrained subject, showed the derived relations. One of the stimuli (B1) from the relational network and two novel stimuli (X1 and X2) were then used to train three different self-discrimination responses on three complex schedules of reinforcement. That is, all 3 subjects were trained to pick X1 if they had not emitted a response, to pick B1 if they had emitted one response only, and to pick X2 if they had emitted two responses only. The 2 pretrained subjects, but not the nonpretrained subject, showed the predicted transformation of self-discrimination response functions in accordance with the relations of sameness, more than, and less than (i.e., no response, pick B2; one response only, pick C1; and two responses only, pick C2). In Experiment 2, 2 new subjects were employed, and the arbitrary relational training and testing phases were modified to control for a procedural artifact that may have contributed to the results of the first experiment. Experiment 2 replicated the findings of Experiment 1. The pattern of results support the utility of a relational frames approach to understanding derived stimulus relations.     

No evidence for self-recognition in a small passerine,the great tit (<Emphasis Type="Italic">Parus major</Emphasis>) judged from the mark/mirror test

Self-recognition is a trait presumed to be associated with high levels of cognition and something previously considered to be exclusive to humans and possibly apes. The most common test of self-recognition is the mark/mirror test of whether an animal can understand that it sees its own reflection in a mirror. The usual design is that an animal is marked with a colour spot somewhere on the body where the spot can only be seen by the animal by using a mirror. Very few species have passed this test, and among birds, only magpies have been affirmatively demonstrated to pass it. In this study, we tested great tits (Parus major), small passerines, that are known for their innovative foraging skills and good problem-solving abilities, in the mirror self-recognition test. We found no indication that they have any ability of this kind and believe that they are unlikely to be capable of this type of self-recognition.     

Observations on the behavior of gibbons (Hylobates leucogenys, H. gabriellae, and H. lar) in the presence of mirrors

Three captive gibbons (Hylobates leucogenys, H. gabriellae, and H. lar) were videotaped in the course of longitudinal exposure to mirrors introduced into their familiar cage or island housing situation. The gibbons, which differed in age, sex, species, and rearing condition, exhibited great individual differences in their behavioral reactions to mirrors, spanning from a minimal reaction dominated by social responses to a dramatic sequence of progressive behavioral change that featured a variety of contingency testing behaviors and included mirror-mediated, self-directed behavior. Additional information on the mirror competence of gibbons was provided by modified mark tests and a hidden object task. The results are discussed in relation to current criteria for self-recognition in primates and factors involved in individual and species differences in reactions to mirror exposure.     

Development of self-recognition in chimpanzees (Pan troglodytes).

Chimpanzees (Pan troglodytes) demonstrate the ability to recognize themselves in mirrors, yet investigations of the development of self-recognition in chimpanzees are sparse. Twelve young chimpanzees, grouped by age, were given mirror exposure and tested for self-recognition and contingent movement. All 6 juveniles, 4 and 5 years old, exhibited mirror-guided, mark-directed behavior and clear evidence of self-recognition. In contrast, among the infants, only the oldest group of 2 1/2-year-olds exhibited clear evidence of self-recognition. All chimpanzees exhibited both self-directed behaviors and contingent movements. These results suggest that self-recognition occurs at a slightly older age in chimpanzees than in human infants. In humans, self-recognition is linked with other cognitive abilities. The results conform to the general pattern that great apes exhibit many cognitive skills comparable to those of 2-year-old humans.     

What guides a search for food that has disappeared? Experiments on cotton-top tamarins (Saguinus oedipus).

When food is launched down a vertically positioned S-shaped opaque tube, cotton-top tamarins (Saguinus oedipus) search for the food in the position directly beneath the release point, even though over several trials it never appears in this position (B. M. Hood et al., 1999). Experiment 1 showed that when the trajectory of the food shifts from the vertical to the horizontal plane, tamarins no longer show systematic perseverative errors and, in general, perform better on this invisible displacement task. Experiment 2 showed that tamarins with experience on the horizontal task show less of a bias when tested on the vertical task but nonetheless fail overall to solve this invisible displacement problem; their performance is substantially worse than it was on the horizontal task. Experiment 3 revealed that when the vertically positioned tube is replaced by an occluded ramp, tamarins consistently search in the compartment below the release point, even though most of the tamarins had experience in Experiments 1 and 2. Overall, results indicate that tamarins have a significant gravity bias when searching for food that has disappeared along the vertical plane but also have more general problems finding food that has moved out of sight.     

Naïve predictions of motion and orientation in mirrors: From what we see to what we expect reflections to do

The study aimed to investigate naïve beliefs regarding the dynamic and static behavior of reflections. In the first three experiments, participants in the study made predictions about the correspondence between real and reflected movements or about the orientation of the reflection of a static object placed in front of a mirror. In Experiments 1 and 2, paper-and-pencil tasks were used and in Experiment 3 participants were asked to make their predictions while imagining that they were facing a mirror. Results revealed that a percentage of undergraduates (ranging from 25% to 35%) were unable to make correct predictions. We classified the errors into types and found that responses either conform to the belief that reflections do the same or that they do the opposite. This suggests an oversimplification of the geometry of mirror reflections in two directions: participants either generalize what they see when movements are parallel to the mirror or what they see when movements are orthogonal to the mirror. Findings from Experiment 4 confirmed that these two expectations fit in with what people perceive in mirrors. Findings from Experiment 5 confirmed that this is also in agreement with the relationship perceived when looking at similar movements and orientations “outside” mirrors.     

Subjective,physiological, and behavioural responses towards evaluatively conditioned stimuli

Evaluative Conditioning (EC) is commonly defined as the change in liking of a stimulus (conditioned stimulus, CS) due to its pairings with an affective unconditioned stimulus (US). In Experiment 1, we investigated effects of repeated stimulus pairings on affective responses, i.e. valence and arousal ratings, pupil size, and duration estimation. After repeatedly pairing the CSs with affective USs, a consistent pattern of affective responses emerged: The CS_negative was rated as being more negative and more arousing, resulted in larger pupils, and was temporally overestimated compared to the CS_neutral. In Experiment 2, the influence of a mere instruction about the contingency between a CS and US on affective responses was examined. After mere instruction about upcoming pairings between the CS and US, subjective ratings also changed, but there was neither evidence for differential pupillary responses nor for differential temporal processing. The results indicate that EC via pairings or instructions can change the affective responses towards formerly neutral stimuli and introduce pupil size as a physiological measure in EC research. However, Experiment 2 suggests that there might be moderating factors based on the type of EC procedure involved.     

A social cichlid fish failed to pass the mark test

Since the pioneering work in chimpanzees, mirror self-recognition (MSR), the ability to recognise oneself in a mirror, has been reported in great apes, Asian elephants, dolphins, and some social birds using the mark test, in which animals that possess MSR touch an imperceptible mark on their own bodies only when a mirror is present. However, giant pandas, which are solitary, failed to pass the mark test, suggesting that MSR evolved solely in highly social animals. In contrast to the increasing evidence of MSR in mammals and birds, little is known about MSR in fish. A Tanganyikan cichlid, Neolamprologus pulcher, is a good candidate for study because these fish live in highly social groups and recognise conspecifics about as rapidly as primates. We examined their responses to a mirror image and tested whether N. pulcher could pass the mark test. When the mirror was first exposed, they stayed in front of the mirror and exhibited aggressive behaviour towards the mirror image. These social behaviours suggested that the focal fish perceived the mirror image as an unfamiliar conspecific. The social responses decreased over the following days, as has generally been the case in animals with MSR. After mark injection, we found no increase in scraping behaviour or prolonged observation of the marked side. These results show a lack of contingency checking and mark-directed behaviours, meaning that N. pulcher failed to pass the mark test and did not recognise their self-image in the mirror.     

Self-focused attention and reactions to fear

Two studies were conducted to study the effect of self-focused attention on behavioral responses to fear. In Experiment 1, phobics and nonphobics were asked to approach and hold a snake either in the presence of a mirror or with no mirror. In Experiment 2, high and low private self-conscious subjects were asked to submit to a series of either mild or strong electric shock for humanitarian reasons. In each case, self-directed attention caused increased responsivity to the fearful affect and made subjects more likely to withdraw from the situation, regardless of the fact that a behavioral standard existed which called for an opposite response. The theoretical and behavioral implications of the findings were discussed.     

Altered grooming responses to stress in rats exposed prenatally to ethanol

The effects of prenatal alcohol exposure on grooming, locomotion, and rearing in response to stress were examined in adult rats whose mothers consumed a liquid diet containing 35% ethanol-derived calories (EDC). Offspring of both pair-fed 0% EDC mothers and ad libitum chow-fed mothers were included as controls. In Experiment 1, females groomed more than males following placement into a novel test chamber, but no differences due to prenatal treatment were observed. Ethanol-exposed animals groomed more than controls following the stress of a forced 1-min swim (Experiment 2), but when rats tested in Experiment 1 were observed again after forced swim stress (Experiment 3), no differences due to prenatal treatment or sex were observed. Experiment 4 examined the effects of pretreatment with 1 mg/kg naloxone on novelty-induced grooming and as in Experiment 1 prenatal treatment did not affect grooming responses. Females again groomed significantly more than males and naloxone reduced grooming equally for all groups. The results suggest that novelty-induced grooming is a sex-influenced behavior, with females grooming more than males, and that animals exposed prenatally to alcohol and tested as adults may have altered responses to certain stressors (i.e., forced swim) under specific conditions. The altered grooming response of alcohol-exposed rats to swim stress can be eliminated by preexposing them to novelty stress.     

A laboratory analogue of mirrored-self misidentification delusion: The role of hypnosis,suggestion, and demand characteristics

Mirrored-self misidentification is the delusional belief that one’s own reflection in the mirror is a stranger. In two experiments, we tested the ability of hypnotic suggestion to model this condition. In Experiment 1, we compared two suggestions based on either the delusion’s surface features (seeing a stranger in the mirror) or underlying processes (impaired face processing). Fifty-two high hypnotisable participants received one of these suggestions either with hypnosis or without in a wake control. In Experiment 2, we examined the extent to which social cues and role-playing could account for participants’ behaviour by comparing the responses of 14 hypnotised participants to the suggestion for impaired face processing (reals) with those of 14 nonhypnotised participants instructed to fake their responses (simulators). Overall, results from both experiments confirm that we can use hypnotic suggestion to produce a compelling analogue of mirrored-self misidentification that cannot simply be attributed to social cues or role-playing.     

Visual reinforcement in the female Siamese fighting fish, Betta splendens

Operant conditioning with Betta splendens (Bettas) has been investigated extensively using males of the species. Ethological studies of female Bettas have revealed aggressive interactions that qualitatively parallel those between male Bettas. Given these similarities, four experiments were conducted with female Bettas to examine the generality of a widely reported finding with males: mirror-image reinforcement. Swimming through a ring was reinforced by a 10-s mirror presentation. As with males, ring swimming was acquired and maintained when mirror presentations were immediate (Experiments 1, 2, and 3) and delayed (Experiment 4). The failure of conventional extinction (Experiments 1 and 2) and response-independent mirror presentations (Experiment 3) to maintain responding confirmed the reinforcing properties of mirror presentation. These results extend previous findings of mirror images as reinforcers in males of the same species and illustrate a complementarity between behavioral ecology and the experimental analysis of behavior.     

Stock optimizing: maximizing reinforcers per session on a variable-interval schedule.

In Experiment 1, 2 monkeys earned their daily food ration by pressing a key that delivered food according to a variable-interval 3-min schedule. In Phases 1 and 4, sessions ended after 3 hr. In Phases 2 and 3, sessions ended after a fixed number of responses that reduced food intake and body weights from levels during Phases 1 and 4. Monkeys responded at higher rates and emitted more responses per food delivery when the food earned in a session was reduced. In Experiment 2, monkeys earned their daily food ration by depositing tokens into the response panel. Deposits delivered food according to a variable-interval 3-min schedule. When the token supply was unlimited (Phases 1, 3, and 5), sessions ended after 3 hr. In Phases 2 and 4, sessions ended after 150 tokens were deposited, resulting in a decrease in food intake and body weight. Both monkeys responded at lower rates and emitted fewer responses per food delivery when the food earned in a session was reduced. Experiment 1's results are consistent with a strength account, according to which the phases that reduced body weights increased food's value and therefore increased subjects' response rates. The results of Experiment 2 are consistent with an optimizing strategy, because lowering response rates when food is restricted defends body weight on variable-interval schedules. These contrasting results may be attributed to the discriminability of the contingency between response number and the end of a session being greater in Experiment 2 than in Experiment 1. In consequence, subjects lowered their response rates in order to increase the number of reinforcers per session (stock optimizing).     

Pavlovian conditioning of distinct components of Hermissenda's responses to rotation

In two experiments with the nudibranch mollusk Hermissenda, distinct characteristics of conditioned and unconditioned responses to high-speed orbital rotation were examined. In Experiment 1, two principle unconditioned responses to rotation were identified, namely, reduced rate of locomotion and contraction of the foot. The magnitude of the foot contraction increased throughout a 20-s period of rotation, whereas locomotion was reduced immediately after the onset of the rotation and was maintained at this constant low rate throughout the stimulus presentation. These divergent response patterns suggest that the two responses emerge independently. In Experiment 2, a classical conditioning procedure was employed in which a light (CS) was paired with the rotation (US) employed in Experiment 1. In a subsequent test, it was found that the light had acquired the capability to evoke both foot contraction and decreased locomotion. Although the magnitude of these conditioned responses was reduced relative to the corresponding unconditioned response, the patterns of responding were virtually identical; that is, foot contraction developed gradually whereas locomotion decreased immediately. In contrast, animals that received unpaired presentations of the light and rotation, light alone, or no prior exposure to those stimuli exhibited foot extension in response to the light. These results illustrate a transfer of some of the response-evoking properties of the US to the CS as a result of conditioning, as well as the emergence of two independent conditioned responses. Moreover, these results suggest modulation of at least two distinct motor pathways as a function of learning.     

Implicit chaining in cotton-top tamarins (Saguinus oedipus) with elements equated for probability of reinforcement

Three experiments examined the implicit learning of sequences under conditions in which the elements comprising a sequence were equated in terms of reinforcement probability. In Experiment 1 cotton-top tamarins (Saguinus oedipus) experienced a five-element sequence displayed serially on a touch screen in which reinforcement probability was equated across elements at .16 per element. Tamarins demonstrated learning of this sequence with higher latencies during a random test as compared to baseline sequence training. In Experiments 2 and 3, manipulations of the procedure used in the first experiment were undertaken to rule out a confound owing to the fact that the elements in Experiment 1 bore different temporal relations to the intertrial interval (ITI), an inhibitory period. The results of Experiments 2 and 3 indicated that the implicit learning observed in Experiment 1 was not due to temporal proximity between some elements and the inhibitory ITI. The results taken together support two conclusion: First that tamarins engaged in sequence learning whether or not there was contingent reinforcement for learning the sequence, and second that this learning was not due to subtle differences in associative strength between the elements of the sequence.     

Are consonant intervals music to their ears? Spontaneous acoustic preferences in a nonhuman primate

Humans find some sounds more pleasing than others; such preferences may underlie our enjoyment of music. To gain insight into the evolutionary origins of these preferences, we explored whether they are present in other animals. We designed a novel method to measure the spontaneous sound preferences of cotton-top tamarins, a species that has been extensively tested for other perceptual abilities. Animals were placed in a V-shaped maze, and their position within the maze controlled their auditory environment. One sound was played when they were in one branch of the maze, and a different sound for the opposite branch; no food was delivered during testing. We used the proportion of time spent in each branch as a measure of preference. The first two experiments were designed as tests of our method. In Experiment 1, we used loud and soft white noise as stimuli; all animals spent most of their time on the side with soft noise. In Experiment 2, tamarins spent more time on the side playing species-specific feeding chirps than on the side playing species-specific distress calls. Together, these two experiments suggest that the method is effective, providing a spontaneous measure of preference. In Experiment 3, however, subjects showed no preference for consonant over dissonant intervals. Finally, tamarins showed no preference in Experiment 4 for a screeching sound (comparable to fingernails on a blackboard) over amplitude-matched white noise. In contrast, humans showed clear preferences for the consonant intervals of Experiment 3 and the white noise of Experiment 4 using the same stimuli and a similar method. We conclude that tamarins' preferences differ qualitatively from those of humans. The preferences that support our capacity for music may, therefore, be unique among the primates, and could be music-specific adaptations.