Findings

Picking a Side

Kevin Lewis

December 27, 2009

Right movies on the right seat: Laterality and seat choice

Matia Okubo
Applied Cognitive Psychology, January 2010, Pages 90-99

Abstract:
Various forms of lateral preferences are found in human behaviour. Conducting two experiments, we investigated the lateral preference for seat choice exhibited by people at the movie theatre. The right-handed participants (N = 269) tended to choose seats to the right of the screen when they were positively motivated to see the movie. This rightward bias disappeared when they were negatively motivated. In addition, the non-right-handed participants (N = 105) did not show any substantial bias in their seat choice. It is well known that visual and emotional information is better processed in the right hemisphere. Considering the visual and emotional nature of movie experiences, the rightward seating bias among right-handers appears to be determined by their motivation to effectively utilize their right-hemisphere functions.

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Embodiment of Abstract Concepts: Good and Bad in Right- and Left-Handers

Daniel Casasanto
Journal of Experimental Psychology: General, August 2009, Pages 351-367

Abstract:
Do people with different kinds of bodies think differently? According to the body-specificity hypothesis, people who interact with their physical environments in systematically different ways should form correspondingly different mental representations. In a test of this hypothesis, 5 experiments investigated links between handedness and the mental representation of abstract concepts with positive or negative valence (e.g., honesty, sadness, intelligence). Mappings from spatial location to emotional valence differed between right- and left-handed participants. Right-handers tended to associate rightward space with positive ideas and leftward space with negative ideas, but left-handers showed the opposite pattern, associating rightward space with negative ideas and leftward with positive ideas. These contrasting mental metaphors for valence cannot be attributed to linguistic experience, because idioms in English associate good with right but not with left. Rather, right- and left-handers implicitly associated positive valence more strongly with the side of space on which they could act more fluently with their dominant hands. These results support the body-specificity hypothesis and provide evidence for the perceptuomotor basis of even the most abstract ideas.

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Influence of handedness and bilateral eye movements on creativity

Elizabeth Shobe, Nicholas Ross & Jessica Fleck
Brain and Cognition, December 2009, Pages 204-214

Abstract:
We investigated the effects of increased inter-hemispheric interaction (IHI) on five creativity dimensions (appropriateness, detail, categorical distinctiveness, fluency, and originality) of the Alternate Uses Task. Two methods were used to indicate degree of IHI. Trait IHI was indicated by individual differences in handedness, mixed-handers showing greater IHI than strong-handers. State IHI was directly manipulated by central (control group) and bilateral viewing conditions of a 30 s eye movement task (EM). Results indicate significantly higher creativity for mixed-handers, as compared to strong-handers, for all five sub-scores separately and linearly combined. Bilateral EM increased originality and categorical distinctiveness (i.e., flexibility) of strong-handers, but had no effect on mixed-handers. Strong-handers in the bilateral EM group were not different from mixed-handers. Additionally, the bilateral EM effect on strong-handers had different durations for originality (up to 7-9 min) and categorical distinctiveness (up to 3 min). The results suggest that greater IHI can facilitate creativity of strong-handers, but that the characteristically higher IHI of mixed-handers was unaffected by the bilateral EM manipulation.

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Organizational effects of fetal testosterone on human corpus callosum size and asymmetry

Lindsay Chura, Michael Lombardo, Emma Ashwin, Bonnie Auyeung, Bhismadev Chakrabarti, Edward Bullmore & Simon Baron-Cohen
Psychoneuroendocrinology, January 2010, Pages 122-132

Abstract:
Previous theory and research in animals has identified the critical role that fetal testosterone (FT) plays in organizing sexually dimorphic brain development. However, to date there are no studies in humans directly testing the organizational effects of FT on structural brain development. In the current study we investigated the effects of FT on corpus callosum size and asymmetry. High-resolution structural magnetic resonance images (MRI) of the brain were obtained on 28 8-11-year-old boys whose exposure to FT had been previously measured in utero via amniocentesis conducted during the second trimester. Although there was no relationship between FT and midsaggital corpus callosum size, increasing FT was significantly related to increasing rightward asymmetry (e.g., Right > Left) of a posterior subsection of the callosum, the isthmus, that projects mainly to parietal and superior temporal areas. This potential organizational effect of FT on rightward callosal asymmetry may be working through enhancing the neuroprotective effects of FT and result in an asymmetric distribution of callosal axons. We suggest that this possible organizational effect of FT on callosal asymmetry may also play a role in shaping sexual dimorphism in functional and structural brain development, cognition, and behavior.

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Is Your Product on the Right Side? The "Location Effect" on Perceived Product Heaviness and Package Evaluation

Xiaoyan Deng & Barbara Kahn
Journal of Marketing Research, December 2009, Pages 725-738

Abstract:
The authors show that location of the product image on a package facade influences consumers' perceptions of the visual heaviness of the product and evaluations of the package. The "heavier" ("lighter") locations are on the bottom (top), right (left), and bottom-right (top-left) of the package. For products for which heaviness is considered a positive attribute, packages with the product image placed at heavy locations are preferred, whereas for products for which heaviness is considered a negative attribute, packages using light locations are preferred. Furthermore, in the former category (e.g., snacks), a salient health goal, as opposed to a neutral goal, weakens the preference for packages using heavy locations, though this moderating effect of goal is weaker for healthful snacks than for regular snacks. Store shelf context is a boundary condition, such that the location effects on perceived product heaviness and package evaluation appear in a contrasting context but disappear in an assimilating context. Moreover, perceived product heaviness mediates (1) the location effect on package evaluation and (2) the moderating role of store shelf context (i.e., mediated moderation).

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Visual Experience Affects Handedness

Sebastian Ocklenburg, Corinna Bürger, Christine Westermann, Daniel Schneider, Heiner Biedermann & Onur Güntürkün
Behavioural Brain Research, forthcoming

Abstract:
In birds, a lateralised visual input during early development importantly modulates morphological and functional asymmetries of vision. We tested the hypothesis that human handedness similarly results from a combination of inborn and experience-driven factors by analysing sidedness in children suffering from congenital muscular torticollis. These children display a permanently tilted asymmetric head posture to the left or to the right in combination with a contralateral rotation of face and chin, which could lead to an increased visual experience of the hand contralateral to the head tilt. Relative to controls, torticollis-children had a higher probability of right- or left-handedness when having a head tilt to the opposite side. No statistical significant relation between head position and direction of functional asymmetries was found for footedness and eye-preference, although the means show a non-significant trend in the same direction as was observed for handedness. Thus, an increased visual control of the hand during early childhood seems to modulate handedness and possibly other lateral preferences to a lesser extent. These findings not only show that human handedness is affected by early lateralised visual experience but also speak in favour of a combined gene-environment model for its development.

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The Left Hand Doesn't Know What the Right Hand Is Doing: The Disruptive Effects of Attention to the Hands in Skilled Typewriting

Gordon Logan & Matthew Crump
Psychological Science, October 2009, Pages 1296-1300

Abstract:
Everyone knows that attention to the details disrupts skilled performance, but little empirical evidence documents this fact. We show that attention to the hands disrupts skilled typewriting. We had skilled typists type words preceded by cues that told them to type only the letters assigned to one hand or to type all of the letters. Cuing the hands disrupted performance markedly, slowing typing and increasing the error rate (Experiment 1); these deleterious effects were observed even when no keystrokes were actually inhibited (Experiment 3). However, cuing the same letters with colors was not disruptive (Experiment 2). We account for the disruption with a hierarchical control model, in which an inner loop controls the hands and an outer loop controls what is typed. Typing letters using only one hand requires the outer loop to monitor the inner loop's output; the outer loop slows inner-loop cycle time to increase the likelihood of inhibiting responses with the unwanted hand. This produces the disruption.

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Hormone exposure and functional lateralisation: Examining the contributions of prenatal and later life hormonal exposure

Victoria Bourne & Dawn Gray
Psychoneuroendocrinology, September 2009, Pages 1214-1221

Abstract:
An increasing amount of research has shown a relationship between hormonal exposure and functional lateralisation. In this study different sources of hormonal exposure were examined: prenatal exposure, estimated using the 2D:4D ratio, and later life exposure through examining the effects of hormone replacement therapy. In addition to considering multiple sources of hormonal exposure, three tests of functional lateralisation were used: two versions of the chimeric faces test, one using positive emotion and the other using negative emotion, and the landmark task. The same effects were found across all three measures of lateralisation. Lower 2D:4D ratios, which indicate high levels of prenatal testosterone exposure, were associated with stronger right hemisphere dominance. Later life hormonal exposure was not found to be associated with any of the lateralisation measures. This finding suggests a relationship between prenatal hormonal exposure and brain organisation.


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