Evidence Of Handedness Research Articles

Evidence of handedness in turtles

AbstractAlthough research supporting cerebral lateralization, or handedness, in non‐human vertebrates is expanding, reptiles represent one of the least studied. While assessing wood turtle shells, we noticed more dents, scrapes, chips, and other forms of damage on the right side of turtles than on the left. Asymmetrical injury has been attributed to cerebral lateralization in other taxa, and current research supports handedness in testudines. After creating a “scute damage index” to catalog damage location, we confirmed turtles had more damage on the right side of their shells than on the left. We offer four hypotheses that explain this pattern.

Life History Traits of the Snapping Shrimp Alpheus carlae (Decapoda: Alpheidae) from the South-eastern Coast of Brazil.

The life history traits of the snapping shrimp Alpheus carlae were investigated. We evaluated the relative growth, morphological sexual maturity, sexual dimorphism, handedness, fecundity, and egg volume. Sampling was performed monthly in an estuarine region of Cananéia, in the south-eastern coast of Brazil. The following structures were measured to perform the relative growth analysis: length of carapace and second pleonal pleuron, length, width and height of major cheliped propodus, and length of appendix interna and appendix masculina. Juveniles and adults males and females have different growth patterns, indicating distinct strategies of energy allocation. The estimated carapace length at the onset of morphological sexual maturity of females and males was 5.6 mm and 6.2 mm, respectively. The sexual dimorphism of specific body structures was evident, mainly in the appendix interna of females and major cheliped of males. There was no evidence of handedness in females or males. The mean fecundity of females was 364 ± 204 eggs (mean ± SD) eggs and was positively correlated with the carapace length. The egg volume differed between developmental stages I and II, and I and III, with an overall volume increase of 73.23% and 95.45%, respectively. The results contribute to the knowledge about A. carlae and its life history in natural environment.

OH-65: The earliest evidence for right-handedness in the fossil record

Labial striations on the anterior teeth have been documented in numerous European pre-Neandertal and Neandertal fossils and serve as evidence for handedness. OH-65, dated at 1.8 mya, shows a concentration of oblique striations on, especially, the left I1 and right I1, I2 and C1, which signal that it was right-handed. From these patterns we contend that OH-65 was habitually using the right hand, over the left, in manipulating objects during some kind of oral processing. In living humans right-handedness is generally correlated with brain lateralization, although the strength of the association is questioned by some. We propose that as more specimens are found, right-handedness, as seen in living Homo, will most probably be typical of these early hominins.

Handedness: What Kangaroos Tell Us about Our Lopsided Brains

Brain asymmetry is widespread, but the presence of handedness in non-human animals is debated. A new study now provides evidence for handedness in bipedal - but not quadrupedal - marsupials.

Clavicular length asymmetries in primates indicative of handedness in daily activity

Handedness is well understood in humans but not for other primates. Some studies in non‐human primates have focused on behaviors such as reaching for food correlated with hemispheric specialization. Other studies reported asymmetry in upper limb bones of Pan troglodytes to support handedness. Given relations of the upper limb and clavicle, we hypothesized that evidence of handedness would be manifest in measurements of clavicular length. We collected data from chimpanzees (n=8), rhesus (n=2), and spider (n=2) monkeys to represent great apes and Old and New World monkeys from the Division of Mammalogy at the American Museum of Natural History. Preliminary results showed a non‐significant but 62% rightward asymmetry in chimpanzees but essentially symmetry in the monkeys. Clearly, a larger sample size is required to explore these findings further. The relationship of the clavicle between the axial and appendicular skeletons means that it is responsible for transmitting a great deal of force. Activities of the handed upper limb may well have a differential effect on the clavicle. Thus, the clavicle may offer a unique approach to recognize handedness even in extinct primates.Grant Funding SourceDo not have funding

The Flexible Bronchoscope: Which Hand Should Hold It?

Cultural understanding of left-hand dominance has passed through the millennia as evidence of brain damage to demonic possession. Different cultures and traditions still regard the left hand as unclean. In the last several decades, lefthandedness has been accepted and now only with some biases. The extent to which we are a right-handed society can be noted by paying very close attention to the objects we use everyday. Right now, I am typing this on a standard QWERTY keyboard with the mouse at my right hand. The scroll bar is on the right of my window, and when I fire my semiautomatic pistol, the shell casings are expelled away from my face out of the right side. (I actually do not even know how to shoot a gun, but the example is interesting.) Thus, it seems interesting that the “classic teaching” for bronchoscopy is that it should be held in the left hand. Why? Fortunately, we do not really grapple with this; there is no data supporting a specific technique and expert opinions are varied. There are no studies from other procedures to perform any systematic review so this Mehta-analysis will have to suffice. We have identified several areas of possible debate supporting the rationale for using the flexible bronchoscope (FB) in a specific hand (Table 1). The issues we conclude are related to design, tradition, bronchoscopist–patient anatomic ergonometry, advanced techniques, and motor learning. The following few paragraphs describe these arguments, and perhaps demonstrate that the FB might be poorly designed for the majority of bronchoscopists in the era of interventional bronchoscopy.

Evidence for handedness in bumblebees

We describe a simple study of how bumblebees (Bombus spp.) behave when visiting florets which are arranged in a circle around a vertical inflorescence. In four species of bees, individuals showed a tendency for rotation in the same direction around each inflorescence on successive visits, i.e., each individual tended to go either clockwise or anticlockwise. Similar behavior has also been observed in mammals including humans. The implications of this tendency to repeat tasks in the same way are discussed, particularly in relation to our understanding of the phenomenon known as flower constancy. In humans, the tendency for individuals to turn in a particular direction is strongly related to handedness. In three of the four bee species there was a significant overall tendency for the bees to rotate in a preferred direction, suggesting that they too may exhibit handedness.

New Observations about the Nile Valley Middle Palaeolithic : Safaha Method and Lateralization of Levallois Flakes

Two new observations about Nile Valley Middle Palaeolithic technology and typology are presented in this paper. One is related to the Levallois reduction sequence and another to the secondary modification of Levallois flakes. Furthermore, the bearing of both observations on such issues as the evidence for handedness and interassemblage variability in the Nile Valley Middle Palaeolithic is examined.

Age‐ and sex‐associated variations in the directional asymmetry of rhesus macaque forelimb bones

Several investigators have questioned the significance of handedness as an explanation of directional forelimb asymmetries, yet little has been done to isolate other explanatory factors. In this investigation, we analyze 61 female and 76 male rhesus macaque skeletons for evidence of age- and/or sex-associated variations in ten forelimb bone measurements. All significant directional asymmetries are found to favor the right side. Although some of these asymmetries are found to favor the right side. Although some of these asymmetries are compatible with the interpretation of muscle hypertrophy associated with preferential use of the right forelimb, the overall pattern suggests that age- and sex-related ontogenetic factors deserve equal consideration. Significant sex differences in asymmetry means are present within and across age groups (juveniles, subadults, and adults), and numerous changes in asymmetry with age are also found. A pattern of decreasing asymmetry with age was found in males, with 40% of the ten measures being asymmetrical in juveniles, 30% in subadults, and 20% in adults. Among females, this pattern is reversed. No significant asymmetries were found for juvenile or subadult females, whereas 40% of the measures were asymmetrical in adult females. We conclude that greater consideration of age- and sex-related factors is necessary when drawing samples for the purpose of investigating asymmetries, and an awareness of trait-specific age and sex patterns of variation is necessary when citing forelimb asymmetries in demographically nonrepresentative populations as evidence of handedness or other behavioral asymmetries.

Buccal striations on fossil human anterior teeth: evidence of handedness in the middle and early Upper Pleistocene

The presence of gross preferentially distributed striations on the buccal surfaces of permanent anterior teeth of Neandertal individuals from La Quina, Hortus and Angles-sur-l'Anglin (France), Saint Brais (Switzerland) and Shanidar (Iraq) has led some authors to hypothesize that Neandertals used stone tools to cut something held between the anterior teeth, inadvertently scratching the enamel at the same time. We also observe these striations on the anterior teeth of Middle Pleistocene hominids from Atapuerca/Ibeas, Spain, on the incisors of La Quina 5, and on one isolated I 1 from Cova Negra, Spain. Macro- and microscopic studies of these striations, together with those striations produced in an experimental study suggest that scratching of these hominid anterior teeth was indeed the result of ante-mortem tool use, producing striations indicating right- (normally) or left-handedness (rarely). These results provide indirect evidence for lateralization of the brain of Middle and early Upper Pleistocene hominids.