David S. Moore

Mental Rotation in Human Infants A Sex Difference

A sex difference on mental-rotation tasks has been demonstrated repeatedly, but not in children less than 4 years of age. To demonstrate mental rotation in human infants, we habituated 5-month-old infants to an object revolving through a 240° angle. In successive test trials, infants saw the habituation object or its mirror image revolving through a previously unseen 120° angle. Only the male infants appeared to recognize the familiar object from the new perspective, a feat requiring mental rotation. These data provide evidence for a sex difference in mental rotation of an object through three-dimensional space, consistently seen in adult populations.

Purification and concentration of DNA from aqueous solutions.

This unit presents basic procedures for manipulating solutions of single‐ or double‐stranded DNA through purification and concentration steps. The , using phenol extraction and ethanol precipitation, is appropriate for the purification of DNA from small volumes (<0.4 ml) at concentrations <1 mg/ml. Isopropanol may also be used to precipitate DNA, as described in an alternate protocol. Three support protocols outline methods to buffer the phenol used in extractions, concentrate DNA using butanol, and extract residual organic solvents with ether. An alternative to these methods is nucleic acid purification using glass beads, and is described here. These protocol may also be used for purifying RNA. The final protocols provide modifications to the that are used for concentrating RNA and extracting and precipitating DNA from larger volumes and from dilute solutions, and for removing ow‐molecular‐weight oligonucleotides and triphosphates.

Six-Month-Olds' Categorization of Natural Infant-Directed Utterances.

In this study, the authors demonstrated that 6-month-old infants are able to categorize natural, 650 Hz low-pass filtered infant-directed utterances. In Experiment 1, 24 male and 24 female infants heard 7 different tokens from 1 class of utterance (comforting or approving). Then, some infants heard a novel test stimulus from the familiar class of tokens; others heard a test stimulus from the unfamiliar class. Infants categorized these tokens as evidenced by response recovery to tokens from the unfamiliar class but not to novel tokens from the familiar class. Experiment 2 confirmed that the infants were able to discriminate between closely matched tokens from within each category, supporting the conclusion that the results of Experiment 1 indicated categorization. The authors discuss both a mechanism that might explain the development of this ability and the mutual adaptation seen in parent-infant communication.

Espousing Interactions and Fielding Reactions: Addressing Laypeople's Beliefs About Genetic Determinism

Although biologists and philosophers of science generally agree that genes cannot determine the forms of biological and psychological traits, students, journalists, politicians, and other members of the general public nonetheless continue to embrace genetic determinism. This article identifies some of the concerns typically raised by individuals when they first encounter the systems perspective that biologists and philosophers of science now favor over genetic determinism, and uses arguments informed by that perspective to address those concerns. No definitive statements can yet be made about why genetic determinism has proven so resilient in the face of empirical evidence pointing up its deficiencies, but conveying the essential interdependence of ‘nature’ and ‘nurture’ to the general public will likely require deployment of the arguments that systems theorists ordinarily use to reject genetic determinism. In addition, the elaboration of new metaphors that focus attention on the dynamic nature of trait construction will likely prove valuable, because re-conceptualizing notions like ‘genes’ and ‘nature’ will probably be one of the most effective ways to help students and the general public abandon the genetic determinism that biologists now recognize as indefensible.

Isolation and Purification of Large DNA Restriction Fragments from Agarose Gels

This unit describes methods for recovering and purifying DNA restriction fragments from agarose gels. The first basic protocol describes electroelution of the fragment of interest from standard agarose gels using buffer‐filled dialysis bags, followed by concentration and purification using an Elutip column. This approach can be used effectively for fragments of all sizes from 50 to 20,000 bp. Electrophoresis directly onto NA‐45 paper is also described and provides relatively high yields for fragments smaller than 2000 bp. Protocols are also provided for separating fragments larger than 1000 bp using low gelling/melting agarose gels and purified by phenol extraction, b‐agarase digestion of the gel, or via glass beads extraction. Sieving agarose gels can also be used to resolve very small DNA fragments. Removing linkers from a fragment using a column rather than a gel is included, followed by a method for estimating DNA concentrations in solution.

The effects of delay on neonatal retention of habituated head-turning☆

Abstract Recovery of neonatal head orientation following auditory habituation was used to examine the effects of intertrial delay. One of two words served as stimuli with criterion orienting and habituation established before the delay. Fifty-six full-term neonates were assigned randomly to one of four delay groups: 10 (control), 55, 100, or 145 s. The percentage of head-turns toward the sound source (with one turn per trial) for blocks of three trials served as the principal dependent variable. Recovery of localized head-turning increased as length of delay increased, with the 100- and 145-s groups showing greater recovery than the 10- and 55-s groups. Infants presented with control trials systematically turned away from the sound source following habituation. Selective sensory adaptation, spontaneous recovery, and short-term memory interpretations of these data are considered.

A Very Little Bit of Knowledge: Re-Evaluating the Meaning of the Heritability of IQ

Richardson and Norgate have argued that two unwarranted assumptions underlie many of the conclusions drawn by adoption study researchers, namely that genetic and environmental influences on phenotypic variation are additive, and that adoption studies approximate a simple randomized-effects design in which genetic and environmental influences on variance do not contaminate one another. As they note, this issue is important because the primary conclusions of such studies – that genetic variation accounts for a significant proportion of variation in psychological characteristics such as IQ – have been widely accepted [Maccoby, 2001; Nuffield Council on Bioethics, 2002; Turkheimer, 2005]. To address the inappropriateness of the assumption of additivity, Richardson and Norgate refer to several works that support the ascendant view that biological and psychological characteristics are constructed during development, when genes interact with local environmental factors that can be influenced by the broader environment. However, it is worth noting that the literature in developmental biology is replete with findings that support this view, so much so that the earlier view that some genes are able to independently cause or contribute to developmental outcomes is effectively indefensible [Coen, 1999; Edelman, 1988; Keller, 2000; Gottlieb, 1998; Jablonka & Lamb, 2005; Lewontin, 2000; Lickliter & Honeycutt, 2003; Michel & Moore, 1995; Moore, 2002; Robert, 2004; Schaffner, 1998]. Because gene-environment interactions are now understood to drive the development of all of our characteristics, the assumption of additivity is never warranted [Nijhout, 2002; Robert, 2000]. Likewise, after reviewing the relevant data, Richardson and Norgate conclude that the assumption that adopted children’s genes are uncorrelated with their adoptive developmental environments is probably unwarranted in many cases as well.

Perception precedes computation: can familiarity preferences explain apparent calculation by human babies?

Two studies of 5-month-old infants explored whether a phenomenon reported by K. Wynn (1992) reflects a familiarity preference instead of a mathematical competence. Experiment 1 was a conceptual replication of Wynns study. When data were analyzed with the relatively liberal statistical approach used by Wynn, the original phenomenon was replicated. However, an analysis of variance revealed that girls and boys behaved in different ways, and that boys did not behave as Wynn would have predicted. Experiment 2 was identical to Experiment 1, with one exception that should not have influenced computation: Infants in this study were completely familiarized with the test displays before testing. Again, the data revealed an interaction involving sex: Boys tended to be influenced by their familiarity with the test displays, whereas girls tended to behave as Wynn would have predicted. These findings are discussed with reference to the literature on sex differences--specifically the finding that male infants are typically immature relative to their female peers--as well as to articles that have been critical or supportive of Wynns conclusions.

Current Thinking About Nature and Nurture

Theories about the origins of people’s biological and psychological characteristics have focused for centuries on the contributions of Nature and Nurture to development. Modern psychologists often maintain that it is an error to ask if Nature or Nurture determines the form of a particular trait, because the two types of factors interact during development. Instead, some of them have argued, the question of importance is: how much does each factor contribute to this process? This is the approach adopted by quantitative behavioral geneticists engaged in twin and/or adoption studies—research designed to yield heritability estimates for a wide variety of traits. In contrast, molecular biologists have learned that the dichotomy at the heart of such questions does not stand up to either conceptual or empirical scrutiny. In fact, it makes little sense to attempt to quantify the extent to which Nature versus Nurture contributes to a trait, precisely because these two classes of factors are always essential to—and interactive during—the development of both biological and psychological characteristics. Therefore, the question of importance is: how are our traits built during development? That is, how is it that genetic factors, proteins, cells, organs, organisms, and populations of individuals co-act to produce phenotypes in development? There are a number of related insights at the center of this discussion, including that the environments and experiences we encounter as we develop get inside of us in ways that alter our biological/genetic functioning, and that biological factors collaborate with environmental factors to build all of our organs, including our brains and their associated behaviors, cognitions, and emotions. Although the conceptualization of Nature and Nurture as dichotomous has a long history, evidence from the biological sciences indicates that it has outlived its usefulness. Consequently, those wishing to teach students about genetics, human nature, inheritance, and development would be well advised to refrain from framing their discussions in terms of this obsolete dichotomy.

Behavioral epigenetics: Behavioral epigenetics

Why do we grow up to have the traits we do? Most 20th century scientists answered this question by referring only to our genes and our environments. But recent discoveries in the emerging field of behavioral epigenetics have revealed factors at the interface between genes and environments that also play crucial roles in development. These factors affect how genes work; scientists now know that what matters as much as which genes you have (and what environments you encounter) is how your genes are affected by their contexts. The discovery that what our genes do depends in part on our experiences has shed light on how Nature and Nurture interact at the molecular level inside of our bodies. Data emerging from the worlds behavioral epigenetics laboratories support the idea that a persons genes alone cannot determine if, for example, he or she will end up shy, suffering from cardiovascular disease, or extremely smart. Among the environmental factors that can influence genetic activity are parenting styles, diets, and social statuses. In addition to influencing how doctors treat diseases, discoveries about behavioral epigenetics are likely to alter how biologists think about evolution, because some epigenetic effects of experience appear to be transmissible from generation to generation. This domain of research will likely change how we think about the origins of human nature. WIREs Syst Biol Med 2017, 9:e1333. doi: 10.1002/wsbm.1333