Sense of Self in Baby Chimpanzees

Philippe Rochat and his colleague tentatively proposed that young infants' propensity to engage in self-perception and systematic exploration of the perceptual consequences of their own action plays and is probably at the origin of an early sense of self: the ecological self. Rochat and Hespos (1997) reported that neonates discriminate between external and self-stimulation. Neonate tended to display significantly more rooting responses (i.e., head turn towards the stimulation with mouth open and tonguing) following external compared to self-stimulation. Rochat et al. (1998) also reported that 2-month-olds showed clear sign of modulation of their oral activity on the pacifier as a function of analog versus non-analog condition. Rochat and his colleague concluded that these observations are interpreted as evidence of self-exploration and the emergence of a sense of self-agency by 2-month-olds. We tried to replicate these findings in infant chimpanzees. We observed rooting responses of three baby chimpanzees in two condition, self-stimulation and external stimulation. In external stimulation condition, the index finger of the experimenter or small stick touched one of the infant's cheeks. In self-stimulation condition, the experimenter took infant's hand and touched his or her cheek with their fingers. In Rochat and Hespos, they recorded and analyzed several measures such as state, head movement, mouth activity and so on. How ever, we analyzed only mouth activities tentatively. We found infant chimpanzees tended to show more rooting responses following external stimulation compared to self-stimulation as well as human infants. We also carried out sucking experiment with two baby chimpanzees. The experimenter held the pacifier and put the artificial nipple into the infant's mouth. A session started when the infant take the nipple inside the his or her mouth. Auditory stimulus, which was a complex tone comprised of six harmonics with equal intensity, was given to the chimpanzee according to the test condition during their sucking. There were four test conditions and each condition consisted with three types of feedback as follows: 1) silent baseline, contingent, and steady, 2) contingent baseline, 1-sec delay, and 3-sec delay, 3) contingent baseline, 6-sec delay, and 12-sec delay, 4) contingent baseline, 1/2 efficiency, and 1/4 efficiency. In test 1, one infant chimpanzee showed decrease of the minimum pressure of sucking in the contingent condition. In test 2, one subject showed shorter intervals of sucking in 3-sec delay condition. This seems to be similar to human infant's. We may be able to postulate ecological self in baby chimpanzees according to the self-exploration. In test 3 and 4, we did not obtain any effects of stimulus conditions. Results of these studies. These studies were conducted as the parts of the chimpanzee development project in Primate Research Institute, Kyoto University, organized by Professor Tetsuro Matsuzawa

The Structure of the X-Ray Emitting Gas in the Hydra-A Cluster of Galaxies

The temperature and abundance structure in the intracluster medium (ICM) of the Hydra-A cluster of galaxies is studied with ASCA and ROSAT. The effect of the large extended outskirts in the point-spread function of the X-Ray Telescope on ASCA is included in this analysis. In the X-ray brightness profile, the strong central excess above a single beta-model, identified in the Einstein and ROSAT data, is also found in the harder energy band (>4keV). A simultaneous fit of five annular spectra taken with the GIS instrument shows a radial distribution of the temperature and metal abundance. A significant central enhancement in the abundance distribution is found, while the temperature profile suggests that the ICM is approximately isothermal with the temperature of ~3.5keV. The ROSAT PSPC spectrum in the central 1'.5 region indicates a significantly lower temperature than the GIS result. A joint analysis of the GIS and PSPC data reveals that the spectra can be described by a two temperature model as well as by a cooling flow model. In both cases, the hot phase gas with the temperature of ~3.5keV occupies more than 90% of the total emission measure within 1'.5 from the cluster center. The estimated mass of the cooler (0.5-0.7keV) component is ~2-6 x 10^9 M_solar, which is comparable to the mass of hot halos seen in non-cD ellipticals. The cooling flow model gives the mass deposition rate of 60+-30 M_solar/yr, an order of magnitude lower than the previous estimation.Comment: 27 pages, 14 figures, AAS LATEX macros v4.0, to appear in The Astrophysical Journa

CANGAROO-III Observation of TeV Gamma Rays from the vicinity of PSR B1 706-44

Observation by the CANGAROO-III stereoscopic system of the Imaging Cherenkov Telescope has detected extended emission of TeV gamma rays in the vicinity of the pulsar PSR B1706$-$44. The strength of the signal observed as gamma-ray-like events varies when we apply different ways of emulating background events. The reason for such uncertainties is argued in relevance to gamma-rays embedded in the "off-source data", that is, unknown sources and diffuse emission in the Galactic plane, namely, the existence of a complex structure of TeV gamma-ray emission around PSR B1706$-$44.Comment: 10 pages, 13 figures, to be published in Ap

Radial Temperature Profiles of X-Ray--Emitting Gas Within Clusters of Galaxies

Previous analyses of ASCA data of clusters of galaxies have found conflicting results regarding the slope of the temperature profile of the hot X-ray gas within clusters, mainly because of the large, energy-dependent point spread function (PSF) of the ASCA mirrors. We present a summary of all ASCA-determined cluster temperature profiles found in the literature, and find a discrepancy in the radial temperature trend of clusters based on which PSF-correction routine is used. This uncertainty in the cluster temperature profile in turn can lead to large uncertainties in the amount of dark matter in clusters. In this study, we have used ROSAT PSPC data to obtain independent relative temperature profiles for 26 clusters, most of which have had their temperature profiles determined by ASCA. Our aim is not to measure the actual temperature values of the clusters, but to use X-ray color profiles to search for a hardening or softening of the spectra with radius for comparison to ASCA-derived profiles. The radial color profiles indicate that outside of the cooling flow region, the temperature profiles of clusters are in general constant. Within 35% of the virial radius, we find a temperature drop of 20% at 10 keV and 12% at 5 keV can be ruled out at the 99% confidence level. A subsample of non-cooling flow clusters shows that the condition of isothermality applies at very small radii too, although cooling gas complicates this determination in the cooling flow subsample. The colors predicted from the temperature profiles of a series of hydrodynamical cluster simulations match the data very well, although they cannot be used to discriminate among different cosmologies. An additional result is that the color profiles show evidence for a central peak in metallicity in low temperature clusters.Comment: 39 pages, 15 embedded Postscript figures, uses aaspp4.sty, accepted for publication in Astrophysical Journa

Discovery of the Central Excess Brightness in Hard X-rays in the Cluster of Galaxies Abell 1795

Using the X-ray data from \ASCA, spectral and spatial properties of the intra-cluster medium (ICM) of the cD cluster Abell 1795 are studied, up to a radial distance of $\sim 12'$ ($\sim 1.3$ $h_{50}^{-1}$ kpc). The ICM temperature and abundance are spatially rather constant, although the cool emission component is reconfirmed in the central region. The azimuthally- averaged radial X-ray surface brightness profiles are very similar between soft (0.7--3 keV) and hard (3--10 keV) energy bands, and neither can be fitted with a single-$\beta$ model due to a strong data excess within $\sim5'$ of the cluster center. In contrast, double-$\beta$ models can successfully reproduce the overall brightness profiles both in the soft and hard energy bands, as well as that derived with the \ROSAT PSPC. Properties of the central excess brightness are very similar over the 0.2--10 keV energy range spanned by \ROSAT and \ASCA. Thus, the excess X-ray emission from the core region of this cluster is confirmed for the first time in hard X-rays above 3 keV. This indicates that the shape of the gravitational potential becomes deeper than the King-type one towards the cluster center. Radial profiles of the total gravitating matter, calculated using the double-$\beta$ model, reveal an excess mass of $\sim 3 \times 10^{13}~ M_{\odot}$ within $\sim 150 h^{-1}_{50}$ kpc of the cluster center. This suggests a hierarchy in the gravitational potential corresponding to the cD galaxy and the entire cluster.Comment: 27 pages, 8 figures; to appear ApJ 500 (June 20, 1998

Chimpanzee Personality and the Arginine Vasopressin Receptor 1A Genotype

Polymorphisms of the arginine vasopressin receptor 1a (AVPR1a) gene have been linked to various measures related to human social behavior, including sibling conflict and agreeableness. In chimpanzees, AVPR1a polymorphisms have been associated with traits important for social interactions, including sociability, joint attention, dominance, conscientiousness, and hierarchical personality dimensions named low alpha/stability, disinhibition, and negative emotionality/low dominance. We examined associations between AVPR1a and six personality domains and hierarchical personality dimensions in 129 chimpanzees (Pan troglodytes) living in Japan or in a sanctuary in Guinea. We fit three linear and three animal models. The first model included genotype, the second included sex and genotype, and the third included genotype, sex, and sex × genotype. All personality phenotypes were heritable. Chimpanzees possessing the long form of the allele were higher in conscientiousness, but only in models that did not include the other predictors; however, additional analyses suggested that this may have been a consequence of study design. In animal models that included sex and sex × genotype, chimpanzees homozygous for the short form of the allele were higher in extraversion. Taken with the findings of previous studies of chimpanzees and humans, the findings related to conscientiousness suggest that AVPR1a may be related to lower levels of impulsive aggression. The direction of the association between AVPR1a genotype and extraversion ran counter to what one would expect if AVPR1a was related to social behaviors. These results help us further understand the genetic basis of personality in chimpanzees