Historical changes in everyday human lifestyles and their effects on hemispheric activation: Speculations on McGilchrist's The Master and His Emissary.

McGilchrist [McGilchrist, I. (2009). The master and His emissary: The divided brain and the making of the modern world. Yale University Press] argued that Western society has undergone a population-level shift from greater right hemisphere influence on cognition to increasingly greater left hemisphere influence over the past few centuries. Four historical lifestyle changes that replaced behaviours associated with right hemisphere activation with behaviours associated with left hemisphere activation may be responsible: (i) shifts from standing to sitting, (ii) from being outdoors to indoors, (iii) from communal to solitary activities, and (iv) from analogue/concrete to holistic/abstract representations.

Differences Between Consistent and Inconsistent Handedness Remain Consistently Interesting: Ten Years of Research on the Consistency of Handedness With the Edinburgh Handedness Inventory.

Almost 10 years ago Prichard et al. (2013) published a literature review on consistency of handedness. They described how consistency of handedness, typically measured by the Edinburgh Handedness Inventory (EHI), predicted outcomes in memory and decision-making paradigms better than direction of handedness. In the last 10 years, new research has extended these findings and added new theoretical perspectives. The goal of this short form review is to highlight and summarize some of these more intriguing findings and to encourage researchers in the fields of memory and decision making to incorporate handedness as a variable in future research.

Righty-tighty, lefty-loosey: relation between societal tightness scores, left-handedness rates, and COVID-19 outcomes in US states.

As the percentage of right-handers increases in a state, the tightness of that state's culture, as measured, also increases. The relations between handedness, tightness, and various COVID measures (cases per 100,000, vaccination rates, hospitalization rates, death rates, and mask wearing adherence) were examined. Left-handedness rates and tightness both marginally predicted COVID cases and significantly predicted vaccination rates (more right-handers and more tightness associated with higher COVID rates and lower vaccination rates), only left-handedness rates predicted mask wearing adherence (more left-handers associated with increased adherence), only tightness predicted death rates (more tightness associated with higher death rates), and neither handedness or tightness predicted hospitalizations. Results are discussed in terms of the connection between consistent right-handedness and decreased cognitive flexibility and its implication for sociopolitical outcomes, and implications for the framing of public health messaging are presented.

Awe Correlates With Resilience to COVID-19 Stressors Independent of Religiosity.

Awe is an emotion defined by an experience of vastness and cognitive accommodation that is unique among other positive emotions in that its cognitive effects are more similar to those of negative emotions. The current study posits that because of its unique cognitive effects, awe may related to resilience to stressors introduced by the COVID-19 pandemic. It was hypothesized that awe would significantly correlate with resilience to COVID-19 even when controlling for religiosity. Religiosity was included in the analyses because of strong support in previous research connecting it to both awe and resilience. Regression analyses revealed that awe and religiosity were both significant correlates of resilience but when placed in the same model, the relationship between religiosity and resilience disappeared. An exploratory mediation analysis was conducted to further explore this result. Implications for understanding resilience in the face of COVID-19 and directions for future research are discussed.

Memory Effects of Manipulating Text Column Width: Eye-Movement Induced Attentional Processes Interfere With Prose Encoding Among Consistent Handers.

Performing bilateral saccadic eye-movements has enhanced subsequent verbal recall among consistent handers (people who use their dominant hands for virtually all tasks) but not inconsistent handers (people who use their non-dominant hands for some tasks); but eye-movements prior to encoding have disrupted recall in consistent handers. We sought to better understand how this research might be applied to recalling written text presented in ways that differentially affected eye movements. We manipulated text column width in order to test whether induced eye movements and resultant right hemisphere activations would lead consistent handed (versus inconsistent handed) readers to experience encoding disruptions and poorer recall of the written passage. We presented participants, divided by handedness consistency and gender, with a story about a fictional island in which the lines of text were either ∼28 or ∼120 characters wide. We later asked participants to answer 20 questions about the story and measured their memory performance by both their percentage of correct answers and by their correct answers adjusted for a guessing tendency. We found a handedness by text width interaction. Consistent handers who read the story in a narrower column width showed poorer recall than both inconsistent handers and consistent handers who read the story in the wider text column. We suggest a chain of events such that text width altered eye-movements that, in turn, activated right hemisphere brain processes associated with orienting attention and attentional control, competing with consistent handers' encoding.

Authoritarianism, Conspiracy Beliefs, Gender and COVID-19: Links Between Individual Differences and Concern About COVID-19, Mask Wearing Behaviors, and the Tendency to Blame China for the Virus.

The present study investigated variables potentially associated with a lack of concern about COVID-19 and belief in the conspiracy theory that China is responsible for the virus. In particular, the study looked at Authoritarianism, Conspiracy Beliefs, gender, and consistency of handedness as predictors of nine Likert-type items gauging attitudes, behavior, and beliefs regarding the virus. Initial analyses showed that Authoritarianism predicted less concern about the impact of the virus on health, less mask wearing, and a stronger belief in China's responsibility for the illness. Conspiracy Beliefs were associated with a stronger belief in China's responsibility. Women expressed greater degrees of concern about their own and others' health and about the financial wellbeing of others. In order to reduce the number of dimensions, and thus the number of tests that could yield a type one error, the nine items were then submitted to a principal components analysis which yielded a "Concern about COVID" factor and a "Blame for China" factor. Authoritarianism is generally associated with less concern about the virus. In addition, men showed less concern about the virus overall than women. Both Authoritarianism and Conspiracy Beliefs accounted for unique variance in blame on China for the virus.

Handedness and the 2016 U.S. Primaries: consistent handedness predicts support for Donald Trump among republicans, but gender predicts support for Hillary Clinton among democrats.

A growing number of studies demonstrate that consistent handers, people who use their dominant hand for all or most manual tasks, are less cognitively flexible than inconsistent handers, people who use their non-dominant hands at least some of the time. A recent hypothesis suggests that differences in handedness emerged evolutionarily because populations benefited from a balance between cognitively rigid and cognitively flexible people. One expectation is that cognitively rigid consistent handers would support more authoritarian policies or candidates. To test this idea, we looked at handedness, gender, and political affiliation as predictors of support for Donald Trump, a candidate whose supporters self-report being more authoritarian, in the 2016 primary. Our data show that in the Republican Primary, consistent handers report more support than inconsistent for Donald Trump. When authoritarianism was added as a covariate, the handedness effect disappeared. Further analyses showed that authoritarianism mediates the relationship between handedness and support for Donald Trump. In the Democratic Primary, there was a main effect of gender. Women reported more support than men for Hillary Clinton.

The Pen Is Not Always Mightier: Different Ways of Measuring Handedness With the Edinburgh Handedness Inventory Yield Different Handedness Conclusions.

Although consistency of handedness (the strength of dominant hand preference) is increasingly recognized as an important individual difference, there are questions about how to best measure it. A recent meta-analysis showed that researchers have often failed to report details of responses and response formats to handedness test items. In addition to measuring handedness direction (i.e., left versus right handedness), there can be utility to dichotomizing the Edinburgh Handedness Inventory (EHI) into consistent and inconsistent dominant handedness, despite controversy over the best means of doing so. In this study, we performed a discriminant function analysis of EHI items to determine which items best predicted handedness consistency versus handedness direction. Although the same discriminant function accounted for most of the variance for both dependent measures, writing and drawing EHI items were the strongest predictors of handedness direction and combing and opening jars items were the strongest predictors of handedness consistency. As different items on the EHI predicted these different handedness dimensions, we discuss the implications of dichotomizing EHI items into both relevant dimensions for both biological and environmental theories of the basis of handedness and for future handedness research.

The association between inconsistent handedness and psychopathy does not extend to the domain of moral reasoning.

A recent study [Shobe, E., & Desimone, K. (2016). Inconsistent handers show higher psychopathy than consistent handers. Laterality: Asymmetries of Body, Brain and Cognition, 21(2), 143-160. doi:10.1080/1357650X.2015.1089879] found an association between inconsistent handedness (the use of one's non-dominant hand for some tasks) and psychopathy. Because this provides evidence for an association between an individual difference and a trait that is perceived negatively, the present study set out to (1) attempt to replicate the finding and (2) determine whether inconsistent handedness and psychopathy predict similar patterns of moral reasoning. An Mturk sample of 344 adults took the Edinburgh Handedness Inventory, the Short Dark Triad Questionnaire, and the Moral Foundations Questionnaire. The finding of a modest association between handedness and psychopathy was replicated. However, handedness and psychopathy predicted totally different response patterns on the Moral Foundations Questionnaire, with psychopathy predicting less concern for others and fairness and inconsistent handedness predicting less respect for authority and less in group loyalty.

Inconsistent-handed advantage in episodic memory extends to paragraph-level materials.

Past research using handedness as a proxy for functional access to the right hemisphere demonstrates that individuals who are mixed/inconsistently handed outperform strong/consistently handed individuals when performing episodic recall tasks. However, research has generally been restricted to stimuli presented in a list format. In the present paper, we present two studies in which participants were presented with paragraph-level material and then asked to recall material from the passages. The first study was based on a classic study looking at retroactive interference with prose materials. The second was modelled on a classic experiment looking at perspective taking and the content of memory. In both studies, the classic effects were replicated and the general finding that mixed/inconsistent-handers outperform strong/consistent-handers was replicated. This suggests that considering degree of handedness may be an empirically useful means of reducing error variance in paradigms looking at memory for prose level material.

Need for cognition moderates paranormal beliefs and magical ideation in inconsistent-handers.

A growing literature suggests that degree of handedness predicts gullibility and magical ideation. Inconsistent-handers (people who use their non-dominant hand for at least one common manual activity) report more magical ideation and are more gullible. The current study tested whether this effect is moderated by need for cognition. One hundred eighteen university students completed questionnaires assessing handedness, self-reported paranormal beliefs, and self-reported need for cognition. Handedness (Inconsistent vs. Consistent Right) and Need for Cognition (High vs. Low) were treated as categorical predictors. Both paranormal beliefs and magical ideation served as dependent variable's in separate analyses. Neither set of tests yielded main effects for handedness or need for cognition. However, there were a significant handedness by need for cognition interactions. Post-hoc comparisons revealed that low, but not high, need for cognition inconsistent-handers reported relatively elevated levels of paranormal belief and magical ideation. A secondary set of tests treating the predictor variables as continuous instead of categorical obtained the same overall pattern.

Factor analysis of the Edinburgh Handedness Inventory: Inconsistent handedness yields a two-factor solution.

While neuropsychology has long focused on direction (left versus right) of handedness, a growing body of evidence indicates that degree (inconsistent versus consistent) of handedness is at least as important. A promising feature of this new emphasis on degree of handedness is its greater concordance with extant genetic models of handedness, which posit a continuum from inconsistent-handedness to consistent right-handedness, not a continuum from left- to right-handedness. Specifically, departures away from consistent-right-handedness are thought to reflect the action of a neutral genetic factor that leaves handedness up to random environmental influences. To test whether handedness in inconsistent-handers reflects the presence of multiple factors (compared to the presence of a single factor only in consistent-right-handers), factor analyses of handedness inventory scores were conducted on data from 987 right-handers, divided into consistent- versus inconsistent-handers. Consistent with predictions, analyses of inconsistent- versus consistent-handers yielded two versus one factor solutions, respectively. Results are discussed in terms of their potential implications for genetic models of handedness and for researchers interested in consistency of handedness as a neuropsychological variable.

Individual differences in information order effects: the importance of right-hemisphere access in belief updating.

The order in which information is received alters the evaluation of causal hypotheses. Specifically, research suggests that the last piece of information oftentimes has the greatest impact on the evaluation and that the difference in subjective value between two pieces of information is an important factor influencing the magnitude of this recency effect. The present paper extends this line of work by exploring individual differences in this phenomenon via one's degree of handedness. Two hundred and five participants were given two hypothetical scenarios and related causal hypotheses accompanied by two pieces of additional information and asked to revise their belief in each hypothesis as information accumulated. Results confirmed predictions that 1) inconsistent/mixed-handers (those who use their non-dominant hand for at least some activities) show a larger effect with two pieces of inconsistent weak or strong information, and 2) neither mixed-handers nor consistent/strong-handers (those who use their dominant hand for almost all activities) show an effect with strong and weak pieces of consistent information. Mixed-handers' susceptibility to persuasive arguments and Ramachandran's (1995; Ramachandran and Blakeslee, 1998) belief-updating theory centered around communication between the two halves of the brain and functional access to the right hemisphere are used to account for these data.