Non-binary and binary transgender youth: Comparison of mental health, self-harm, suicidality, substance use and victimization experiences.

Background : Little research has compared the mental health and victimization experiences of non-binary youth depending on their sex assigned at birth (SAAB), or compared these two groups with binary transgender youth. Aims : To compare mental health, self-harm and suicidality, substance use and victimization experiences between non-binary and binary transgender young adults, both male assigned at birth (MAAB) and female assigned at birth (FAAB). Methods : Online survey data from 677 participants from the "Youth Chances" community study of 16 to 25 year olds in the United Kingdom was analyzed, comparing across binary participants (transgender females (n = 105) and transgender males (n = 210)) and non-binary participants (MAAB (n = 93) and FAAB (n = 269)). Results : Female SAAB participants (binary and non-binary) were more likely to report a current mental health condition and history of self-harm than male SAAB participants (binary and non-binary). Similarly, female SAAB participants (binary and non-binary) were more likely to report childhood sexual abuse than male SAAB participants (binary and non-binary); the reverse pattern was found for lifetime physical assault relating to being LGBTQ. Non-binary MAAB participants were less likely than the other groups to report past suicide attempts and previous help-seeking for depression/anxiety. Binary participants reported lower life satisfaction than non-binary participants. For all four groups, mental health problems, self-harm, suicidality, alcohol use and victimization experiences were generally higher than that of youth in general population studies. Conclusions : These findings highlight the importance of considering both non-binary versus binary gender identity and SAAB in relation to mental health problems, self-harm, suicidality and substance use in transgender youth. The roles of sexual abuse, other abuse and discrimination in contributing to increased rates of mental illness and self-harm in non-binary and binary transgender individuals, particularly those who were assigned female at birth, relative to those assigned male, require investigation.

Overestimation of stereo thresholds by the TNO stereotest is not due to global stereopsis.

PURPOSE: It has been repeatedly shown that the TNO stereotest overestimates stereo threshold compared to other clinical stereotests. In the current study, we test whether this overestimation can be attributed to a distinction between 'global' (or 'cyclopean') and 'local' (feature or contour-based) stereopsis. METHODS: We compared stereo thresholds of a global (TNO) and a local clinical stereotest (Randot Circles). In addition, a global and a local psychophysical stereotest were added to the design. One hundred and forty-nine children between 4 and 16 years old were included in the study. RESULTS: Stereo threshold estimates with TNO were a factor of two higher than with any of the other stereotests. No significant differences were found between the other tests. Bland-Altman analyses also indicated low agreement between TNO and the other stereotests, especially for higher stereo threshold estimates. Simulations indicated that the TNO test protocol and test disparities can account for part of this effect. DISCUSSION: The results indicate that the global - local distinction is an unlikely explanation for the overestimated thresholds of TNO. Test protocol and disparities are one contributing factor. Potential additional factors include the nature of the task (TNO requires depth discrimination rather than detection) and the use of anaglyph red/green 3D glasses rather than polarizing filters, which may reduce binocular fusion.

Efficient estimation of stereo thresholds: What slope should be assumed for the psychometric function?

Bayesian staircases are widely used in psychophysics to estimate detection thresholds. Simulations have revealed the importance of the parameters selected for the assumed subject's psychometric function in enabling thresholds to be estimated with small bias and high precision. One important parameter is the slope of the psychometric function, or equivalently its spread. This is often held fixed, rather than estimated for individual subjects, because much larger numbers of trials are required to estimate the spread as well as the threshold. However, if this fixed value is wrong, the threshold estimate can be biased. Here we determine the optimal slope to minimize bias and maximize precision when measuring stereoacuity with Bayesian staircases. We performed 2- and 4AFC disparity detection stereo experiments in order to measure the spread of the disparity psychometric function in human observers assuming a Logistic function. We found a wide range, between 0.03 and 3.5 log10 arcsec, with little change with age. We then ran simulations to examine the optimal spread using the empirical data. From our simulations and for three different experiments, we recommend selecting assumed spread values between the percentiles 60-80% of the population distribution of spreads (these percentiles can be extended to other type of thresholds). For stereo thresholds, we recommend a spread around the value σ = 1.7 log10 arcsec for 2AFC (slope ß = 4.3 /log10 arcsec), and around σ = 1.5 log10 arcsec for 4AFC (ß = 4.9 /log10 arcsec). Finally, we compared a Bayesian procedure (ZEST using the optimal σ) with five Bayesian procedures that are versions of ZEST-2D, Psi, and Psi-marginal. In general, for the conditions tested, ZEST optimal σ showed the lowest threshold bias and highest precision.

Two choices good, four choices better: For measuring stereoacuity in children, a four-alternative forced-choice paradigm is more efficient than two.

PURPOSE: Measuring accurate thresholds in children can be challenging. A typical psychophysical experiment is usually too long to keep children engaged. However, a reduction in the number of trials decreases the precision of the threshold estimate. We evaluated the efficiency of forced-choice paradigms with 2 or 4 alternatives (2-AFC, 4-AFC) in a disparity detection experiment. 4-AFC paradigms are statistically more efficient, but also more cognitively demanding, which might offset their theoretical advantage in young children. METHODS: We ran simulations evaluating bias and precision of threshold estimates of 2-AFC and 4-AFC paradigms. In addition, we measured disparity thresholds in 43 children (aged 6 to 17 years) with a 4-AFC paradigm and in 49 children (aged 4 to 17 years) with a 2-AFC paradigm, both using an adaptive weighted one-up one-down staircase. RESULTS: Simulations indicated a similar bias and precision for a 2-AFC paradigm with double the number of trials as a 4-AFC paradigm. On average, estimated threshold of the simulated data was equal to the model threshold, indicating no bias. The precision was improved with an increasing number of trials. Likewise, our data showed a similar bias and precision for a 2-AFC paradigm with 60 trials as for a 4-AFC paradigm with 30 trials. Trials in the 4-AFC paradigm took slightly longer as participants scanned more alternatives. However, the 4-AFC task still ended up faster for a given precision. CONCLUSION: Bias and precision were similar in a 4-AFC task compared to a 2-AFC task with double the number of trials. However, a 4-AFC paradigm was more time efficient and is therefore recommended.

Nestling testosterone is associated with begging behaviour and fledging success in the pied flycatcher, Ficedula hypoleuca.

Animal signals are hypothesized to be costly in order to honestly reflect individual quality. Offspring solicitation signals given by nestling birds are thought to have evolved to advertise either need or individual quality. We tested the potential role of testosterone (T) in controlling the intensity of these signals by measuring begging behaviour as: (i) duration of the begging display and (ii) maximum height of the begging stretch, and by sampling endogenous T levels in nestling blood. We tested nestling pied flycatchers (Ficedula hypoleuca) using well-established experimental paradigm involving transient food deprivation to encourage begging behaviour and then blood-sampled nestlings at the end of these tests for T levels. Our results show that individual nestlings with the most intense begging displays had the highest circulating levels of T immediately after testing. In addition, we found substantial differences between broods in terms of circulating T. Finally, we found evidence that broods with higher levels of T showed increased fledging success, indicating a benefit for increased T production in nestlings. The potential trade-offs involved in T-mediated begging behaviour are discussed.

Was basking important in the evolution of mammalian endothermy?

The first mammals were small, nocturnal, and presumably had low metabolic rates and were therefore probably unable to maintain a constant high body temperature throughout cool nights. How these animals, without sufficient heat production for endogenous rewarming, were able to become warm and active again before the next activity period remains unresolved. However, we discovered that, similar to reptiles, the carnivorous marsupial mammal Pseudantechinus macdonnellensis (body mass 30.8 +/- 5.0 g) uses the morning sun to rewarm from low (26.3 +/- 4.5 degrees C) body temperatures during torpor. Our findings provide the first evidence of basking during rewarming from torpor in mammals and may provide an alternative explanation as to how ancestral mammals could have become nocturnal to avoid diurnal predators despite their small size and a low endogenous heat production.