John D. Jasper

Individual differences in risk perception versus risk taking: handedness and interhemispheric interaction.

Research indicates that right-hemisphere mechanisms are specifically sensitive to and averse to risk. Research also indicates that mixed degree of handedness is associated with increased access to right hemisphere processing. Accordingly, it was predicted that mixed-handers would exhibit greater risk aversion. Participants were presented with various risky activities and were asked to rate (i) the perceived risk, (ii) the perceived benefit, and (iii) their likelihood to engage in each activity. No handedness differences were found for any of these ratings. Regression analyses, however, indicated that the likelihood to engage in risky activities was predicted primarily by the perceived risks in mixed-handers and by the perceived benefits in strong-handers.

Individual differences in ambiguous-figure perception: degree of handedness and interhemispheric interaction.

Research has shown that persons with strong right-hand preference (ie who report using their dominant hand for all manual activities) display a decreased tendency to update bodily and conceptual representations, possibly arising from decreased interaction between the left and right cerebral hemispheres. Current experiments extend these findings to the domain of perceptual representations. In experiments 1 and 2, strong right-handedness was associated with a decreased ability to update perceptual representations in response to gradually changing perceptual input. In experiment 3, strong right-handedness was associated with lower spontaneous reversal rates during the extended viewing of ambiguous figures, and experiment 4 ruled out an explanation in terms of response bias.

Individual differences in semantic switching flexibility: Effects of handedness

The semantic fluency task is a widely used assessment tool for evaluating memory-related cognitive deficits in neurological and neuropsychiatric disorders. The present study investigates individual differences in performance on this task in a normal population. The aim is to explore handedness differences in switching and clustering tendencies when performing this task. Consistent with our prediction, when asked to produce as many animal names as possible in 1 min, mixed handers demonstrated greater switching between different subcategories of animals than strong handers. These findings are interpreted in terms of the more diffuse spread of activation among conceptual representations in the right hemisphere, and greater access to right hemisphere processes in mixed handers. The findings have implications for the research communities using the semantic fluency task, irrespective of whether or not they are looking at handedness differences per se.

Inaction Inertia, the Sunk Cost Effect, and Handedness: Avoiding the Losses of Past Decisions.

Strength of handedness, or the degree to which an individual prefers to use a single hand to perform various tasks, is a neurological marker for brain organization and has been shown to be linked to episodic memory, attribute framing, and anchoring, as well as other domains and tasks. The present work explores the relationship of handedness to both inaction inertia (the inclination to resist an action after previously bypassing a similar action) as well as to the sunk cost effect (the tendency to continue to engage in a behavior after an initial investment of time or money has been made). In Experiment 1, mixed-handers displayed a larger inaction inertia effect than strong-handers. In Experiment 2, they displayed a larger sunk cost effect than strong-handers. Experiments 3 and 4 extended the sunk cost finding into a different domain and explored how mixed- and strong-handers react to additional information designed to increase the comparative advantage of terminating, rather than continuing, a failed project. Overall, we found that mixed-handers were more likely to show inertia effects because of an increased aversion to losses. The results of Experiment 4 suggest that, when provided with additional information that made it clear that continuing a project would be a greater loss than terminating it, mixed-handers no longer showed a larger sunk cost effect than strong-handers, highlighting the importance of carefully considering exactly how sunk cost scenarios are worded and providing additional information on how mixed- and strong-handers differ in belief updating.

Responding to framed health messages: Different strokes for different (handedness) folks

Research has shown that strength of handedness – a proxy variable for the degree of interaction between the left and right brain hemispheres – predicts differences in a variety of cognitive domains. The present paper extends this work to message (or goal) framing effects in which persuasive health communications emphasise positive vs. negative outcomes. One hundred fifty-six participants read pamphlets containing statements emphasising either the gains of using or the losses of not using sunscreen. Replicating previous research, non-users of sunscreen were more affected by framed messages than users. However, we found a loss- rather than gain-framed advantage, and mixed (inconsistent)-handers seemed to drive these effects more so than strong (consistent)-handers. These results suggest that a ‘one-size-fits-all’ approach may be inadequate in crafting effective educational messages about health behaviours, and that theories centring around one’s regulatory focus orientation as well as new methods in laterality research may be useful in reaching the widest range of individuals.

Handedness differences in information framing.

Previous research has shown that strength of handedness predicts differences in sensory illusions, Stroop interference, episodic memory, and beliefs about body image. Recent evidence also suggests handedness differences in the susceptibility to common decision biases such as anchoring and sunk cost. The present paper extends this line of work to attribute framing effects. Sixty-three undergraduates were asked to advise a friend concerning the use of a safe allergy medication during pregnancy. A third of the participants received negatively-framed information concerning the fetal risk of the drug (1-3% chance of having a malformed child); another third received positively-framed information (97-99% chance of having a normal child); and the final third received no counseling information and served as the control. Results indicated that, as predicted, inconsistent (mixed)-handers were more responsive than consistent (strong)-handers to information changes and readily update their beliefs. Although not significant, the data also suggested that only inconsistent handers were affected by information framing. Theoretical implications as well as ongoing work in holistic versus analytic processing, contextual sensitivity, and brain asymmetry will be discussed.

Interhemispheric interaction and egocentrism: The role of handedness in social comparative judgement

Previous research has shown that people are egocentrically biased when making judgements that require a self-to-peer comparison - leading to above-/below-average effects and comparative optimism/pessimism. Two experiments examined whether interhemispheric brain connectivity (assessed via strength of handedness) is associated with egocentrism in the comparative judgement process. In Experiment 1, strong handers (SH) and mixed handers (MH) made percentile rank judgements about their abilities in easy and hard domains. In Experiment 2, SH and MH judged their likelihoods of outperforming a co-participant in easy and hard tasks. Both experiments showed that SH were more egocentric than MH and thus showed (a) more above- and below-average effects when estimating their abilities (Experiment 1) and (b) generally larger optimism biases when predicting performances in a competition (Experiment 2). Taken together, these experiments provide evidence that underlying interhemispheric connectivity shapes egocentrism in comparative judgement.

Handedness predicts motivation to switch from the status quo

Degree of handedness is a correlate of structural brain asymmetries and predicts individual differences in episodic memory, belief updating and various biases in decision-making. We examined whether handedness moderated the status quo bias given previous research suggests that both constructs are related to loss aversion. Participants answered hypothetical scenarios in which they decided either to stay with the status quo or to switch. Results indicated that consistent and inconsistent right-handers both exhibited status quo bias (Experiment 1; N = 180), but inconsistent right-handers were more (or less) likely to stick with the status quo when informed of a positive (or negative) past experience. When provided with more equivocal information about the quality of the status quo and alternative, consistent-handers (CH) were more likely to show a status quo bias (Experiment 2; N = 222). Compared to CH, we argue that inconsistent-handers (IH) more readily update their beliefs in a manner consistent with how the status quo and alternative options are presented—switching when finding a reason to favour the alternative and staying when the status quo is described more favourably. These handedness differences fit a motivational account explaining status quo bias rather than a loss aversion account.

The effects of varying levels of hemispheric activation on episodic memory

ABSTRACT Bilateral saccadic eye movements enhance episodic memory retrieval; however, this usually only occurs for consistent-handed, not inconsistent-handed, individuals. It was hypothesized that inconsistent-handers begin closer to the peak of a Yerkes–Dodson-type inverted-U curve and increasing activation pushes them along the curve eventually decreasing performance, while consistent-handers start at a lower baseline and therefore increasing activation increases their performance. The current study tested this hypothesis by using hand clenching (grip strength) to increase activation at 5 different levels for both consistent- and inconsistent-handers. A total of 316 participants were presented with a list of 36 words after which they squeezed a hand dynamometer to induce cortical activation, and then recalled as many of the words as they could. Results showed that, as predicted, both inconsistent- and consistent-handers demonstrated an inverted-U pattern of memory performance as the strength of squeeze increased with inconsistent-handers peaking at a lower level of grip strength than consistent-handers. These results may help explain past findings, not only with episodic memory but also a variety of other cognitive tasks. They may also have interesting theoretical and real-world implications, which are discussed.

Enhanced activation of the left hemisphere promotes normative decision making

Previous studies have reported that enhanced activation of the left cerebral hemisphere reduces risky-choice, attribute, and goal-framing effects relative to enhanced activation of the right cerebral hemisphere. The present study sought to extend these findings and show that enhanced activation of the left hemisphere also reduces violations of other normative principles, besides the invariance principle. Participants completed ratio bias (Experiment 1, N = 296) and base rate neglect problems (Experiment 2, N = 145) under normal (control) viewing or with the right or left hemisphere primarily activated by imposing a unidirectional gaze. In Experiment 1 we found that enhanced left hemispheric activation reduced the ratio bias relative to normal viewing and a group experiencing enhanced right hemispheric activation. In Experiment 2 enhanced left hemispheric activation resulted in using base rates more than normal viewing, but not significantly more than enhanced right hemispheric activation. Results suggest that hemispheric asymmetries can affect higher-order cognitive processes, such as decision-making biases. Possible theoretical accounts are discussed as well as implications for dual-process theories.