MEG analysis of "theory of mind" in emotional vignettes comprehension.

OBJECTIVE: Several studies suggested that an impaired "theory of mind" might play a key role in psychiatric disorders, such as autism and schizophrenia. Medial frontal lobe lesions of the right frontal lobe were reported to impair this ability. The aim of our study was to locate areas of the brain associated with the process of "theory of mind" in normal subjects. METHODS: In order to index the activity of brain areas related to "theory of mind" reasoning in sixteen normal adults, we administered an emotional ("happy", "sad", "angry" and "neutral") vignettes comprehension task during magnetoencephalography (MEG) recordings and analyzed these data by using SAM (synthetic aperture magnetometry), SPM99 and the permutation method. Subjects were presented with eight different videotaped social situations (each emotion has two vignettes) and were asked to indicate which emotion they represented. RESULTS: Statistically significant activation in the comparison of "happy"-"sad" and "angry"-"sad" was observed in the bilateral medial prefrontal cortices in the alpha frequency band. There were no significant differences in comparisons of each type of emotional vignette to the neutral vignettes, "happy"-"angry" comparison, and male-female comparisons. There was no significant difference in other frequency bands. CONCLUSION: This result suggests that bilateral medial prefrontal cortex are involved in the comprehension of emotional states of others.

The fireside hypothesis: was there differential selection to tolerate air pollution during human evolution?

It is believed that sometime around 1.9 million years ago early hominid ancestors began to migrate out of Africa. Migration north and away from the equator would have forced early humans to encounter seasonal fluctuations in temperature. As a means of adapting to cold climates, the use of fire undoubtedly played an important role. We hypothesize that progressive exposure to toxic airborne particles produced from combustion created selective pressure to develop an adaptation to the inhalation of smoke. In this paper we test this hypothesis using archival data on the incidence of different cancers among geographically distinct human populations. As predicted from evolutionary theory, the incidence of lung cancer is inversely proportional to the ostensible reliance on fire of geographically different groups during human evolutionary history.

Sex differences in olfactory self-recognition.

This study investigated sex differences in the ability to recognize one's own body odor accompanied by an attempt to account for variance in this ability by comparing ratings of self-body odor and other odors on a visual analog scale (VAS). Whereas over half (59.4%) of the females were able to identify their own odor, only one out of 18 (5.6%) males were able to recognize their own odor. Females rated their own secretions as significantly lower on a pleasant-positive factor than males rated their own odors (axillary secretions), but there was no difference in ratings between those who could and those who could not identify their own odor. The dimensions tapped by the VAS used in this study do not seem to account for the ability to identify one's own body odors.

The frontal lobes are necessary for 'theory of mind'.

Patients with limited focal frontal and nonfrontal lesions were tested for visual perspective taking and detecting deception. Frontal lobe lesions impaired the ability to infer mental states in others, with dissociation of performance within the frontal lobes. Lesions throughout the frontal lobe, with some suggestion of a more important role for the right frontal lobe, were associated with impaired visual perspective taking. Medial frontal lesions, particularly right ventral, impaired detection of deception. The former may require cognitive processes of the lateral and superior medial frontal regions, the latter affective connections of the ventral medial frontal with amygdala and other limbic regions.

Left hand advantage in a self-face recognition task.

Subjects were exposed to pictures of self and others (e.g., friend, stranger, and famous people) to determine if there was an advantage in reaction time and accuracy in identifying the self. It was found that upright and inverted self-faces were identified more rapidly than non-self faces when subjects responded with their left hand, which in other tasks has corresponded with contralateral hemispheric dominance. These data suggest that self-recognition may be correlated with neural activity in the right hemisphere, and that the differences observed may not be unique to self-face recognition. These results are in agreement with previous research indicating that self-directed awareness is correlated with right prefrontal activity.

Self-awareness and the evolution of social intelligence.

The use of one's own experience as a model to make inferences about the experiences of others is theorized to be the means by which a variety of introspectively based social strategies developed for both competing and cooperating with one another (e.g. gratitude, grudging, sympathy, empathy, deception, pretending and sorrow). The proposition that this ability is a byproduct of self-awareness is developed in some detail and the predictions which follow from this model of social intelligence are considered in light of the evidence.

Age differences in the ability of chimpanzees to distinguish mirror-images of self from video images of others.

To evaluate Heyes's (1994) claim that chimpanzees are incapable of using mirrored information to obtain otherwise unavailable information about the self, we exposed two different age groups of chimpanzees (3-year-olds and 7- to 10-year-olds) to mirrors and video images of conspecifics. Their reactions to these stimuli were videotaped and were later scored for behavioral indices of self-recognition by a trained observer who was blind to the purpose and conditions of the study. Some types of behavior (contingent facial and body movements) were clearly influenced by the type of stimulus that the chimpanzees were viewing but not by age; however, other behaviors (self-exploration) were affected by age in conjunction with the type of stimulus the animals were viewing. The results suggest that, unlike self-exploratory behavior, contingent facial and body movements may not, by themselves, be reliable indicators of self-recognition.

Social responding to mirrors in rhesus monkeys (Macaca mulatta): effects of temporary mirror removal.

As a result of a long-term, longitudinal project initiated in 1978, a pair of rhesus macaques (Macaca mulatta) housed together in front of a mirror all their lives now exhibit relatively little interest in their reflection. Previous work has shown, however, that simply moving the mirror to a new location produces a short-term reinstatement of social responding to their images. As an extension of these findings, in this study the mirror was left in the same position but turned away from the cage. On turning the mirror back to face the cage 5 days later, both animals reacted as if confronted with another pair of monkeys and directed a burst of social responses at the mirror.

Thermal correlates of tonic immobility and social isolation in chickens.

Previous research has shown that core temperature in chickens drops following the induction of tonic immobility (TI), while hyperthermic trends emerge shortly after response termination. Other research has shown that birds placed in social isolation also become hyperthermic. Since testing for TI is usually carried out while animals are isolated, there is a question as to whether the hyperthermic reaction after the termination of TI has any relation to the episode of TI itself as opposed to being due to the effects of social isolation per se. The present series of studies found that although social isolation did produce significantly longer durations of TI and that the core temperature of isolated birds was affected, when core temperatures were independently raised or lowered, no significant differences were found in TI durations relative to controls. Additionally, in contrast to core temperature changes, shank temperature showed the opposite effect, while another peripheral temperature measure, wing temperature, remained stable.

Chlordiazepoxide and tonic immobility: a paradoxical enhancement.

Four experiments were conducted with chickens to examine the effects of chlordiazepoxide on tonic immobility, which has been implicated as an innate fear response. Not only did chlordiazepoxide produce a paradoxical dose-dependent increase in the duration of tonic immobility, but birds treated with chlordiazepoxide showed significantly enhanced shock-termination thresholds. Using two separate tolerance paradigms, the enhancement due to chlordiazepoxide was shown to be independent of the sedative and/or muscle relaxant effects of the drug. These findings have interesting implications for the supposed anxiolytic effects of the benzodiazepines and the relationship between fear and serotonin in avian species.

Apparent analgesic effects of morphine in chickens may be confounded by motor deficits.

Three experiments were conducted with chickens to examine the effects of morphine on nociception and motor coordination. In Experiment 1, using shock-elicited vocalization as an index of pain, doses of 5, 20, and 30 mg/kg of morphine failed to affect vocalization thresholds. In the second experiment, 30 mg/kg of morphine failed to affect vocalization thresholds at varying times since injection. In Experiment 3, 30 mg/kg of morphine significantly impaired movement in response to nonaversive stimulation. These results show that previous evidence for an analgesic effect of morphine in chickens may have been due to morphine effects on motor initiation and/or coordination.

Face touching in primates: a closer look.

Dimond and Harries (Neuropsychologia 22, 227-233, 1984) claim that monkeys, unlike great apes and humans, rarely touch their faces. These authors reported the existence of a left-hand preference for face touching in great apes and humans. Using two species of macaques, we found an incidence of face touching by monkeys which was much higher than that reported by Dimond and Harries. Moreover, a re-analysis of their data failed to show any evidence for species differences in lateralization of face touching by primates.

Do minds exist in species other than our own?

An answer to the question of animal awareness depends on evidence, not intuition, anecdote, or debate. This paper examines some of the problems inherent in an analysis of animal awareness, and whether animals might be aware of being aware is offered as a more meaningful distinction. A framework is presented which can be used to make a determination about the extent to which other species have experiences similar to ours based on their ability to make inferences and attributions about mental states in others. The evidence from both humans and animals is consistent with the idea that the capacity to use experience to infer the experience of others is a byproduct of self-awareness.

Open-field behaviour in chickens: A replication revisited.

In an attempt to show that the open field can still be used as a valid measure of fear, Jones (1983) has reported a failure to replicate some of our findings. The present studies show that this was due to procedural and methodological differences. For instance, we found that birds tested in a novel environment behaved quite differently from those, as in Jones' case, which were placed in one resembling the home cage. Moreover, birds housed in isolation for two days prior to testing reacted differently than those, as again in Jones' case, which were reared in isolation from hatching to the time of testing. The results were interpreted as being consistent with our view that open-field behaviour reflects a conflict between the need to reinstate contact with conspecifics on the one hand, and evade predation on the other.

Open-field behavior in guinea pigs: Developmental and adaptive considerations.

Two experiments were conducted with guinea pigs to test implications of a model which holds that social reinstatement tendencies and attempts to evade predation are the primary factors influencing how organisms initially react when placed in an open field. Because of the age-related reduction in need for maternal care, vocalization and ambulation latencies increased with age, and in support of the hypothesis that humans are perceived as predators, subjects tested in the presence of a human observer were less likely to move or vocalize than those tested alone. The data on vocalization latencies strongly suggest that the species- specific "whistle" of guinea pigs is a functional mammalian analog to the so-called "distress call" of domestic fowl.