Lynn Wright

The valence-specific laterality effect in free viewing conditions: The influence of sex, handedness, and response bias

The right hemisphere has often been viewed as having a dominant role in the processing of emotional information. Other evidence indicates that both hemispheres process emotional information but their involvement is valence specific, with the right hemisphere dealing with negative emotions and the left hemisphere preferentially processing positive emotions. This has been found under both restricted (Reuter-Lorenz & Davidson, 1981) and free viewing conditions (Jansari, Tranel, & Adophs, 2000). It remains unclear whether the valence-specific laterality effect is also sex specific or is influenced by the handedness of participants. To explore this issue we repeated Jansari et al.s free-viewing laterality task with 78 participants. We found a valence-specific laterality effect in women but not men, with women discriminating negative emotional expressions more accurately when the face was presented on the left-hand side and discriminating positive emotions more accurately when those faces were presented on the right-hand side. These results indicate that under free viewing conditions women are more lateralised for the processing of facial emotion than are men. Handedness did not affect the lateralised processing of facial emotion. Finally, participants demonstrated a response bias on control trials, where facial emotion did not differ between the faces. Participants selected the left-hand side more frequently when they believed the expression was negative and the right-hand side more frequently when they believed the expression was positive. This response bias can cause a spurious valence-specific laterality effect which might have contributed to the conflicting findings within the literature.

Are left-handers really more anxious?

Research examining anxiety and handedness is inconclusive. Davidson and Schaffer (1983) found left-handers had higher trait anxiety, while Beaton and Moseley (1991) found no state or trait differences. Such studies potentially have methodological issues, and we have argued that handedness related reactivity differences (Wright & Hardie, 2011) suggest that state anxiety needs to be measured within a context. Thus the current study investigated state and trait anxiety levels in an experimental situation. We found left-handers had significantly higher state scores, supporting the right hemispheres role in negative affect and inhibition. It also fits with predictions based on the behavioural inhibition systems role in the revised reinforcement sensitivity theory (rRST). No trait differences were found, but there was a significant relationship between trait and state anxiety. Using ANCOVA to control for the influence of trait anxiety on state anxiety, we still found a handedness effect. When participants trait anxiety levels were similar, left-handers showed a relatively larger state response. We conclude that in the context of an experiment, state anxiety was directly correlated with trait anxiety but that the relatively higher reactivity of left-handers may be a major influence on how they respond in a new situation.

Differences between left- and right-handers in approach/avoidance motivation: influence of consistency of handedness measures.

Hand preference is often viewed as a troublesome variable in psychological research, with left-handers routinely excluded from studies. Contrary to this, a body of evidence has shown hand preference to be a useful variable when examining human behavior. A recent review argues that the most effective way of using handedness as a variable, is a comparison between individuals who use their dominant hand for virtually all manual activities (consistent handers) versus those who use their other hand for at least one activity (inconsistent handers). The authors contend that researchers should only focus on degree of handedness rather than direction of preference (left versus right). However, we argue that the field suffers from a number of methodological and empirical issues. These include a lack of consensus in choice of cut-off point to divide consistent and inconsistent categories and importantly a paucity of data from left-handers. Consequentially, researchers predominantly compare inconsistent versus consistent right-handers, largely linked to memory, cognition and language. Other research on response style and personality measures shows robust direction of handedness effects. The present study examines both strength and direction of handedness on self-reported behavioral inhibition system (BIS) and behavioral activation system (BAS) scores, using evidence from a large (N = 689) dataset including more than 200 left-handers. There were degree of handedness effects on BIS and BAS-Fun Seeking, but effects are largely driven by differences between consistent left-handers and other groups. Choice of cut-off point substantively influenced results, and suggests that unless a suitable sample of left-handers is included, researchers clarify that their degree of handedness effects are applicable only to right-handers. We concur that strength of hand preference is an important variable but caution that differences related to consistency may not be identical in right and left-handers.

Pause before you respond: handedness influences response style on the Tower of Hanoi task

Comparative laterality research has indicated that marmoset monkeys with a right‐hand preference take less time to respond to novel objects within a novel environment (Cameron & Rogers, 1999). This suggests that right hemisphere dominance may be associated with a more cautious cognitive style in novel situations. The present study tested this hypothesis using right‐ and left‐handed human participants to complete a three‐disk Tower of Hanoi (TOH) task. It was hypothesised that left‐handers would be slower to initiate responding. A total of 84 participants (42 left‐handers, 42 right‐handers) took part and the time taken to make the first move, completion time, and the number of moves taken to complete the task were recorded. Analysis of Variance revealed a significant main effect of handedness, with left‐handers taking longer to move the first disk and significantly fewer moves to complete the task. However, left‐handers were not significantly faster at completing the TOH, although males completed the task more quickly than females. These initial findings support the hypothesis that left‐hand dominance is associated with a more cautious cognitive style in novel problem‐solving situations.

The enigma of facial asymmetry: is there a gender-specific pattern of facedness?

Although facial symmetry correlates with facial attractiveness, human faces are often far from symmetrical with one side frequently being larger than the other (Kowner, 1998). Smith (2000) reported that male and female faces were asymmetrical in opposite directions, with males having a larger area on the left side compared to the right side, and females having a larger right side compared to the left side. The present study attempted to replicate and extend this finding. Two databases of facial images from Stirling and St Andrews Universities, consisting of 180 and 122 faces respectively, and a third set of 62 faces collected at Abertay University, were used to examine Smiths findings. Smiths unique method of calculating the size of each hemiface was applied to each set. For the Stirling and St Andrews sets a computer program did this automatically and for the Abertay set it was done manually. No significant overall effect of gender on facial area asymmetry was found. However, the St Andrews sample demonstrated a similar effect to that found by Smith, with females having a significantly larger mean area of right hemiface and males having a larger left hemiface. In addition, for the Abertay faces handedness had a significant effect on facial asymmetry with right-handers having a larger left side of the face. These findings give limited support for Smiths results but also suggest that finding such an asymmetry may depend on some as yet unidentified factors inherent in some methods of image collection.

“Not ready to sort it yet”: Revised reinforcement sensitivity theory (rRST) predicts left-handed behavioural inhibition during a manual sorting task

Wright, Hardie, and Rodway (2004) showed that left-handers were slower to respond initially to the Tower of Hanoi, and proposed that this was due to either anxious or inhibited behaviour in their approach or to right hemisphere superiority in spatial tasks. The revised reinforcement sensitivity theory (Gray & McNaughton, 2000) offers a rationale for the influence of anxiety, and Wright, Hardie, and Wilson (2009) demonstrated a behavioural inhibition system (BIS) difference related to handedness, arguing that, due to their increased BIS sensitivity, left-handers may show more anxiety-induced goal conflict and should take longer to initiate any novel task. On the basis of this, the current study tested the prediction of increased left-handed inhibition of action, using a manual sorting task. A total of 78 participants took part and analyses revealed that left-handers took significantly longer to move the first card. A significant handedness×sex interaction was found for task completion time. The significant initiation difference further supports the idea that rBIS sensitivity differences may be the source of divergent responses in novel tasks, rather than hemispheric dominance related withdrawal (Davidson, 1995), and provides support for the new role of BIS in the revised rather than original reinforcement sensitivity theory (Gray, 1982).

Handedness and social anxiety: Using Bryden's research as a catalyst to explore the influence of familial sinistrality and degree of handedness

ABSTRACT Phil Brydens work has impacted on many areas of laterality, including degree and measurement of hand preference, as well as influences of familial sinistrality (FS). For example, Bryden[(1977). Measuring handedness with questionnaires. Neuropsychologia, 15, 617–624] is a well-cited and influential paper that remains relevant to this day. Inspired by this we extended our analysis of the relationship between handedness and anxiety in a number of ways. We used familial handedness and strength of handedness to examine their potential influences on anxiety, and extended our research by exploring their relationship to social anxiety, using the Social Phobia Inventory (SPIN). Inconsistent left-handers (ILH) were found to be more socially anxious. In all categories of SPIN except avoidance, ILH were significantly more anxious than consistent right- and left-handers. There were FS differences between ILH with a first degree left-handed relative (FS+) compared to ILH with no first degree left-handed relative (FS−) on all categories of anxiety scores. Within FS+ participants, ILH had significantly higher anxiety scores, compared with consistent handers across all categories. This suggests that ILHs social anxiety may be influenced by a close left-handed relative. Inspired by examining Brydens work for this special issue, we will continue to add both strength of preference and familial handedness to our work.

Left-handers look before they leap: handedness influences reactivity to novel Tower of Hanoi tasks

A sample of 203 task naïve left- and right-handed participants were asked to complete a combination of the 3- and 4-disk Towers of Hanoi (ToH), manipulating novelty and complexity. Self-reported state anxiety and latency to respond (initiation time) were recorded before each ToH. Novelty had a major effect on initiation time, particularly for left-handers. Left-handers had a longer latency to start and this was significantly longer on the first trial. Irrespective of hand-preference, initiation time reduced on the second trial, however, this was greatest for left-handers. Condition of task did not systematically influence initiation time for right handers, but did for left-handers. State anxiety was influenced by task novelty and complexity in a more complicated way. During the first trial, there was a significant handedness × number of disks interaction with left-handers having significantly higher state anxiety levels before the 3-disk ToH. This suggests that the initial reaction to this task for left-handers was not simply due to perceived difficulty. On their second trial, participants completing a novel ToH had higher state anxiety scores than those completing a repeated version. Overall, left-handers had a larger reduction in their state anxiety across trials. Relating to this, the expected strong positive correlation between state and trait anxiety was absent for left-handed females in their first tower presentation, but appeared on their second. This was driven by low trait anxiety individuals showing a higher state anxiety response in the first (novel) trial, supporting the idea that left-handed females respond to novelty in a way that is not directly a consequence of their trait anxiety. A possible explanation may be stereotype threat influencing the behavior of left-handed females.

Monochrome Males and Colorful Females: Do Gender and Age Influence the Color and Content of Drawings?

Influences of educational level and gender were examined through free drawings. A total of 216 participants were recruited ranging from nursery school to university students. Using an adaptation of Turgeon’s methodology, participants were given a standardized set of colored pens and asked to draw a picture. Pictures were analyzed for the area of the page covered, colors used, number of colors used, and content. Overall, females covered more of the page, and used more colors than males. Females drew significantly more sky, flowers/trees and buildings (in most cases houses), and males drew more people and vehicles. In relation to educational level, nursery children used fewer colors than the other groups and secondary school children used more colors than primary school children. It was concluded that gender differences in content, and color, of drawings exist and these differences remain stable into adulthood. Results are discussed in terms of social and evolutionary theory.

On the Other Hand: Left and Right Brain, Mental Disorder and History

The book opens with a quote by Michael Corballis relating to the fact that there is very little agreement on defining and measuring handedness, yet individuals clearly identify as right- or left-ha...