Nature Of Individual Variation Research Articles

Biased Estimates of Environmental Impact in the Negative Footprint Illusion: The Nature of Individual Variation.

People consistently act in ways that harm the environment, even when believing their actions are environmentally friendly. A case in point is a biased judgment termed the negative footprint illusion, which arises when people believe that the addition of “eco-friendly” items (e.g., environmentally certified houses) to conventional items (e.g., standard houses), reduces the total carbon footprint of the whole item-set, whereas the carbon footprint is, in fact, increased because eco-friendly items still contribute to the overall carbon footprint. Previous research suggests this illusion is the manifestation of an “averaging-bias.” We present two studies that explore whether people’s susceptibility to the negative footprint illusion is associated with individual differences in: (i) environment-specific reasoning dispositions measured in terms of compensatory green beliefs and environmental concerns; or (ii) general analytic reasoning dispositions measured in terms of actively open-minded thinking, avoidance of impulsivity and reflective reasoning (indexed using the Cognitive Reflection Test; CRT). A negative footprint illusion was demonstrated when participants rated the carbon footprint of conventional buildings combined with eco-friendly buildings (Study 1 and 2) and conventional cars combined with eco-friendly cars (Study 2). However, the illusion was not identified in participants’ ratings of the carbon footprint of apples (Study 1 and 2). In Studies 1 and 2, environment-specific dispositions were found to be unrelated to the negative footprint illusion. Regarding reflective thinking dispositions, reduced susceptibility to the negative footprint illusion was only associated with actively open-minded thinking measured on a 7-item scale (Study 1) and 17-item scale (Study 2). Our findings provide partial support for the existence of a negative footprint illusion and reveal a role of individual variation in reflective reasoning dispositions in accounting for a limited element of differential susceptibility to this illusion.

Toward an individual-difference perspective on phonologization

Phonologization is often understood to be a process along the pathway of sound change where low-level physiological or perceptual variation that gives rise to sound patterns is explicitly encoded in the grammar. The nature of this transition and how it comes about remain largely unclear. The broad theoretical goal of this paper is to argue that phonologization should be defined at the level of the individual; it takes place whenever an individual acquires a so-called “phonetic precursor” as an intended, and controlled, pattern in the language, even if the pattern exhibits gradient properties. To illustrate this perspective, a case study on the nature of individual variation in vowel duration as a function of vowel height in Cantonese is presented, offering evidence that some Cantonese speakers have phonologized the height-dependent vowel duration effect and discussing the implications of this result for understanding intrinsic vowel duration as a phonetic precursor to sound change. The article closes with a discussion regarding the current proposal in relation to past models of phonologization and offers suggestions for future directions in phonologization research.

Dexterity and technique in termite fishing by chimpanzees (Pan troglodytes troglodytes) in the Goualougo Triangle, Republic of Congo

Although the phenomenon of termite fishing by chimpanzees (Pan troglodytes) has historical and theoretical importance for primatology, we still have a limited understanding of how chimpanzees accomplish this activity, and in particular, about details of skilled actions and the nature of individual variation in fishing techniques. We examined movements, hand positions, grips, and other details from remote video footage of seven adult and subadult female chimpanzees using plant probes to extract Macrotermes muelleri termites from epigeal nests. Six chimpanzees used exclusively one hand (left or right) to grip the probe during termite fishing. All chimpanzees used the same repertoire of actions to insert, adjust, and withdraw the probe but differed in the frequency of use of particular actions. Chimpanzees have been described as eating termites in two ways—directly from the probe or by sweeping them from the probe with one hand. We describe a third technique: sliding the probe between the digits of one stationary hand as the probe is extracted from the nest. The sliding technique requires complementary bimanual coordination (extracting with one hand and grasping lightly with the other, at the same time). We highlight the importance of actions with two hands—one gripping, one assisting—in termite fishing and discuss how probing techniques are correlated with performance. Additional research on digital function and on environmental, organismic, and task constraints will further reveal manual dexterity in termite fishing.

A multi‐trait, field‐based examination of personality in a semi‐aquatic turtle

AbstractStudies documenting and quantifying personality traits are common in animal behavior. Such studies often consider the nature of individual variation and personality as correlated with a variety of natural history, physiological, or ecological traits, and therefore consider the importance of personality for strategies in wild systems. Though such studies have contributed markedly to our understanding of the important aspects of personality that may covary with a variety of factors that might affect fitness, much of the research on animal personalities is taxonomically limited. To supplement and compliment the laboratory study of reptile personality, we examined the patterns of multiple personality traits in wild Eastern painted turtles (Chrysemys picta) in the field. We examined patterns of aggression, sociability, and boldness across these traits in different contexts in 103 adult, wild‐caught turtles. We found strong correlations both within and among the focal behavioral axes, representing robust evidence for personality in this species. Specifically, we found strong relationships among many measures of aggression, as well as relationships between aggression and our measures of boldness. Finally, we note a tendency for sociability in our turtles, with animals scoring high on sociability showing lower tendency toward aggression. Overall, our study provides robust evidence for correlated suites of behavioral traits, or personality, in a semi‐aquatic turtle surveyed in the wild. Future work should continue to expand the range of traits examined to more fully consider the ecological consequences of variation in personality in this and similar species.

Analysis of Individual Variability among Older Adults on the Stroop Color Word Interference Test

The present study examines systematic variation in the pattern of response to the Stroop test among a sample of older adults (N = 41), as well as the extent to which various configural patterns of response are related to other individual difference factors. Pattern analysis identified four reasonably prototypic patterns of performance. Three significant discriminant functions, capable of differentiating the four response patterns, were significantly and uniquely related to age, level of cautiousness, and verbal intelligence, respectively. The analyses suggest that performance on the Stroop test is multidimensional with significant variation among older adults, and that different components of performance are differentially related to unique individual difference variables. The findings reinforce the importance of recognizing and understanding the nature of individual variation among elderly individuals in aging research.

Variation and control of specific antigen-binding cell populations in individual fetal mice.

To determine the extent and nature of individual variation in the development of specific antigen-binding cells, the numbers of cells specific for each of two antigens in the spleens of individual random-bred Swiss-L and inbred CBA/J and BALB/c fetal mice were measured as a function of spleen size. For Swiss-L fetuses, the ratio of antigen-binding cells to nucleateated cells varied more than would arise from sampling fluctuation. For each inbred strain, however, the number of cells specific for a given antigen was a constant proportion of the total number of nucleated cells within sampling error. These proportions varied from antigen to antigen, and from strain to strain. The ratio of the proportions of cells specific for the two antigens, however, differed no more from CBA/J to BALB/c mice than would be expected in repeated samples of cells from the spleen of a single fetus. These results confirm at the level of the individual fetus the uniform pattern of development seen for populations of fetuses. They reveal a surprising precision in the proliferation of specific antigen-binding cell populations and suggest that the development of these cells may be subject to strong genetic controls.