Ashok Jansari

Non-random associations of graphemes to colours in synaesthetic and non-synaesthetic populations

This study shows that biases exist in the associations of letters with colours across individuals both with and without grapheme-colour synaesthesia. A group of grapheme-colour synaesthetes were significantly more consistent over time in their choice of colours than a group of controls. Despite this difference, there were remarkable inter-subject agreements, both within and across participant groups (e.g., a tends to be red, b tends to be blue, c tends to be yellow). This suggests that grapheme-colour synaesthesia, whilst only exhibited by certain individuals, stems in part from mechanisms that are common to us all. In addition to shared processes, each population has its own distinct profile. Synaesthetes tend to associate higher frequency graphemes with higher frequency colour terms. For control participants, choices are influenced by order of elicitation, and by exemplar typicality from the semantic class of colours.

Hemispheric perception of emotional valence from facial expressions.

The authors previously reported that normal subjects are better at discriminating happy from neutral faces when the happy face is located to the viewers right of the neutral face; conversely, discrimination of sad from neutral faces is better when the sad face is shown to the left, supporting a role for the left hemisphere in processing positive valence and for the right hemisphere in processing negative valence. Here, the authors extend this same task to subjects with unilateral cerebral damage (31 right, 28 left). Subjects with right damage performed worse when discriminating sad faces shown on the left, consistent with the prior findings. However, subjects with either left or right damage actually performed superior to normal controls when discriminating happy faces shown on the left. The authors suggest that perception of negative valence relies preferentially on the right hemisphere, whereas perception of positive valence relies on both left and right hemispheres.

Things that go bump in your life : Explaining the reminiscence bump in autobiographical memory

Two experiments explore the reminiscence bump (RB)--the disproportionately higher recall of early-life memories--by older adults. In Experiment 1, participants in the age ranges of 36-40, 46-50, and 56-60 recalled events freely or under instructions to avoid recent memories. Constraint did not affect older participants but resulted in the appearance of an RB in younger participants. In Experiment 2, recall was constrained to particular life periods. Memories from these periods were compared for ease of retrieval and along subjective dimensions (e.g. vividness). Memories from early life were more easily retrieved, but this was not due to differences in subjective qualities. A higher proportion of memories for first-time events were identified from early life, and these memories were more easily retrievable. The results are discussed in relation to an existing model of autobiographical memory, and a revised model is put forward.

A valence-specific lateral bias for discriminating emotional facial expressions in free field.

Findings from subjects with unilateral brain damage, as well as from normal subjects studied with tachistoscopic paradigms, argue that emotion is processed differently by each brain hemisphere. An open question concerns the extent to which such lateralised processing might occur under natural, freeviewing conditions. To explore this issue, we asked 28 normal subjects to discriminate emotions expressed by pairs of faces shown side-by-side, with no time or viewing constraints. Images of neutral expressions were shown paired with morphed images of very faint emotional expressions (happiness, surprise, disgust, fear, anger, or sadness). We found a surprising and robust laterality effect: When discriminating negative emotional expressions, subjects performed significantly better when the emotional face was to the left of the neutral face; conversely, when discriminating positive expressions, subjects performed better when the emotional face was to the right. We interpret this valence-specific laterality effect as consistent with the idea that the right hemisphere is specialised to process negative emotions, whereas the left is specialised to process positive emotions. The findings have important implications for how humans perceive facial emotion under natural conditions.

Assessing the functional significance of ecstasy-related memory deficits using a virtual paradigm.

Previous research shows that the use of ecstasy results in working memory and executive impairments in some users. The present study sought to assess the functional significance of such deficits using a virtual reality task.

Mental imagery and synaesthesia: Is synaesthesia from internally-generated stimuli possible?

Previous studies provide empirical support for the reported colour experience in grapheme-colour synaesthesia by measuring the synaesthetic experience from an externally presented grapheme. The current study explored the synaesthetic experience resulting from a visual mental image of a grapheme. Grapheme-colour synaesthetes (N=6) and matched controls (N=10 per synaesthete) completed a visual mental imagery task that involved visualising a letter and making a size-based decision about it. The background colour that the grapheme was visualised against was manipulated so that it was congruent or incongruent with the synaesthetic colour for the grapheme being visualised. Compared to matched controls, an effect of colour condition was found for four of the six synaesthetes, although importantly the direction of the effect varied between synaesthetes. In addition, a significant effect of group was found, as the synaesthetes were all faster than the matched controls at the imagery task, regardless of background colour. We conclude that there is some support for subjective reports of imagery-induced synaesthesia, but there are important individual differences. These findings are discussed in relation to both the visual imagery and synaesthesia literature.

The effects of a modest dose of alcohol on executive functioning and prospective memory

Acute alcohol intoxication selectively impairs executive functioning and prospective memory (PM). Much previous researches in this area have used laboratory‐based tasks that may not mimic functions that individuals with dysexecutive syndrome have problems with in their everyday life. The present study aimed to assess the effects of a modest dose of alcohol on executive functioning and PM using a virtual reality task and investigate the role of executive planning in PM performance.

Identifying facial emotions: valence specific effects and an exploration of the effects of viewer gender

The valence hypothesis suggests that the right hemisphere is specialised for negative emotions and the left hemisphere is specialised for positive emotions (Silberman & Weingartner, 1986). It is unclear to what extent valence-specific effects in facial emotion perception depend upon the gender of the perceiver. To explore this question 46 participants completed a free view lateralised emotion perception task which involved judging which of two faces expressed a particular emotion. Eye fixations of 24 of the participants were recorded using an eye tracker. A significant valence-specific laterality effect was obtained, with positive emotions more accurately identified when presented to the right of centre, and negative emotions more accurately identified when presented to the left of centre. The valence-specific laterality effect did not depend on the gender of the perceiver. Analysis of the eye tracking data showed that males made more fixations while recognising the emotions and that the left-eye was fixated substantially more than the right-eye during emotion perception. Finally, in a control condition where both faces were identical, but expressed a faint emotion, the participants were significantly more likely to select the right side when the emotion label was positive. This finding adds to evidence suggesting that valence effects in facial emotion perception are not only caused by the perception of the emotion but by other processes.

Cannabis-related deficits in real-world memory

Research shows that cannabis users exhibit deficits in prospective memory (PM) and executive function, which persist beyond acute intoxication. However, many studies rely on self‐reports of memory failures or use laboratory‐based measures that may not mimic functional deficits in the real world. The present study aimed to assess real‐world memory functioning.

An inability to exclude visual noise in migraine.

PURPOSE People with migraine are relatively poor at judging the direction of motion of coherently moving signal dots when interspersed with noise dots drifting in random directions, a task known as motion coherence. Although this has been taken as evidence of impoverished global pooling of motion signals, it could also arise from unreliable coding of local direction (of each dot), or an inability to segment signal from noise (noise-exclusion). The aim of this study was to determine how these putative limits contribute to impoverished motion processing in migraine. METHODS Twenty-two participants with migraine (mean age, 34.7 ± 8.3 years; 16 female) and 22 age- and sex-matched controls (mean age, 34.4 ± 6.2 years) performed a motion-coherence task and a motion-equivalent noise task, the latter quantifying local and global limits on motion processing. In addition, participants were tested on analogous equivalent noise paradigms involving judgments of orientation and size, so that the specificity of any findings (to visual dimension) could be ascertained. RESULTS Participants with migraine exhibited higher motion-coherence thresholds than controls (P = 0.01, independent t-test). However, this difference could not be attributed to deficits in either local or global processing since they performed normally on all equivalent noise tasks (P > 0.05, multivariate ANOVA). CONCLUSIONS These findings indicate that motion perception in the participants with migraine was limited by an inability to exclude visual noise. We suggest that this is a defining characteristic of visual dysfunction in migraine, a theory that has the potential to integrate a wide range of findings in the literature.