Joël Dickinson

Sex and genetic background influence Superoxide dismutase (cSOD) related phenotypic variation in Drosophila melanogaster

Mutations often have drastically different effects in different genetic backgrounds; understanding a gene’s biological function then requires an understanding of its interaction with genetic diversity. The antioxidant enzyme cytosolic copper/zinc superoxide dismutase (cSOD) catalyzes the dismutation of the superoxide radical, a molecule that can induce oxidative stress if its concentration exceeds cellular control. Accordingly, Drosophila melanogaster lacking functional cSOD exhibit a suite of phenotypes including decreased longevity, hypersensitivity to oxidative stress, impaired locomotion, and reduced NADP(H) enzyme activity in males. To date, cSOD-null phenotypes have primarily been characterized using males carrying one allele, cSodn108red, in a single genetic background. We used ANOVA, and the effect size partial eta squared, to partition the amount of variation attributable to cSOD activity, sex, and genetic background across a series of life history, locomotor, and biochemical phenotypes associated with the cSOD-null condition. Overall, the results demonstrate that the cSOD-null syndrome is largely consistent across sex and genetic background, but also significantly influenced by both. The sex-specific effects are particularly striking and our results support the idea that phenotypes cannot be considered to be fully defined if they are examined in limited genetic contexts.

Do You 'See' What I 'See'? Differentiation of Visual Action Words

Dickinson and Szeligo (Can J Exp Psychol 62(4):211–222, 2008) found that processing time for simple visual stimuli was affected by the visual action participants had been instructed to perform on these stimuli (e.g., see, distinguish). It was concluded that these effects reflected the differences in the durations of these various visual actions, and the results were compared to participants’ subjective ratings of word meaning but it was also possible that word characteristics like length might have influenced response times. The present study takes advantage of word length differences between French and English visual action words in order to address this issue. The goals of the present study were to provide evidence that (1) the processing time differences previously found were due to differences in the cognitive actions represented by these words (and not due to characteristics to the words themselves), and (2) that individuals subjectively differentiate visual action words in such a way that allows for predictable differences in behaviour. Participants differentiated 14 French visual action words along two dimensions. Four of these words were then used in the instructions for a size-discrimination task. Processing time depended on the visual action word in the instruction to the task and differed in a predictable manner according to word meaning but not word length.

Examining the Utility of the New Raney Vocabulary Measure Alongside the WAIS-III

Psychometric tests related to vocabulary assessments are, for the most part, restricted in their use by trained professionals and/or are costly. These restrictions limit their use, especially for research purposes. To circumvent these limitations, the Raney Vocabulary Measure was created for assessing vocabulary proficiency, specifically for research purposes. The measure consists of 30 questions where participants were instructed to choose the best definition of each word. The purpose of the study was to examine the utility of the new measure using the highly standardized but protected Wechsler Adult Intelligence Scale. Results from the linear combination of the subscales revealed the significant prediction of the Raney Vocabulary Measure, with the Vocabulary subtest contributing most to the unique variance. These results support that the test examines vocabulary ability. The current results are promising as the test would allow for greater accessibility for researchers who do not have access to restricted psychometric tests.

The use of the Duchenne marker and symmetry of the expression in the judgment of smiles in schizophrenia

Research has recurrently shown that individuals with schizophrenia have impairments in emotional facial recognition and this deficit has been associated with aberrant visual scanning of the face. Because human beings have the ability to control the expression of emotion, the communication process becomes more complex. The goal of the current study was to conduct a systematic examination of the response pattern and perceptual-attentional processing in distinguishing smiles with the presence and absence of the Duchenne marker and symmetry and asymmetry of the activation in individuals with schizophrenia. Sixteen individuals diagnosed with schizophrenia and 16 control individuals were asked to judge whether the smiles were really happy or not. Individuals with schizophrenia produced fewer expected responses than controls in judging the symmetric non-Duchenne smile as not really happy. In addition, like their healthy counterparts, individuals with schizophrenia showed difficulty with the judgement of asymmetric Duchenne smiles. In addition to not being as sensitive to the cues, individuals with schizophrenia show differences in their viewing patterns. While the current study does not provide clear links between these viewing patterns and judgment responses, future research should explore other explanations, such as explicit knowledge, for the differences in results.

Distinction between fear and surprise: an interpretation-independent test of the perceptual-attentional limitation hypothesis

ABSTRACT The perceptual-attentional limitation hypothesis posits that the confusion between emotional facial expressions of fear and surprise may be due to their visual similarity, with shared muscle movements. In Experiment 1 full face images of fear and surprise varying as a function of distinctiveness (mouth index, brow index, or both indices) were displayed in a gender oddball task. Experiment 2, in a similar task, directed attention toward the eye or mouth region with a blurring technique. The current two studies used response time and event-related potentials (ERP) to test the perceptual-attentional limitation hypothesis. While ERP results for Experiment 1 suggested that individuals may not have perceived a difference between the emotional expressions in any of the conditions, response time results suggested that individuals processed a difference between fear and surprise when a distinctive cue was in the mouth. With directed attention in Experiment 2, ERP results indicated that individuals were capable of detecting a difference in all the conditions. In effect, the current two experiments suggest that participants display difficulty in distinguishing the prototypes of fear and surprise with the eye region, which may be due to a lack of attention to that region, providing support for the attentional limitation hypothesis.

Using Implicit Instructional Cues to Influence False Memory Induction

Previous research has shown that explicit cues specific to the encoding process (endogenous) or characteristic of the stimuli themselves (exogenous) can be used to direct a reader’s attentional resources towards either relational or item-specific information. By directing attention to relational information (and therefore away from item-specific information) the rate of false memory induction can be increased. The purpose of the current study was to investigate if a similar effect would be found by manipulating implicitly endogenous cues. An instructional manipulation was used to influence the perceptual action participants performed on word stimuli during the encoding of DRM list words. Results demonstrated that the instructional conditions that encouraged faster processing also led to an increased rate of false memory induction for semantically related words, supporting the hypothesis that attention was directed towards relational information. This finding supports the impoverished relational processing account of false memory induction. This supports the idea that implicitly endogenous cues, exogenous cues (like font) or explicitly endogenous cues (like training) can direct attentional resources during encoding.