Evolution of an instinct under long-term divergent selection for geotaxis in domesticated populations of Drosophila melanogaster

Long-term divergent selection for geotaxis in lines of Drosophila melanogaster (the fruit fly) is described. After 26 years (600+ generations) of intermittent selection, the mean geotactic scores now remain stable upon relaxed selection, a result suggesting that evolutionary changes have occurred in these lines. Because the stability is not due to genetic fixation (homozygosity) of the lines, it must be due to either close linkage of genes associated with geotaxis (which would not result in enduring change) or the development of new coadapted gene complexes utilizing genes associated with extreme geotaxis expression (which should result in enduring change). Better evidence for the latter hypothesis is obtained from the low, than from the high, line. The notions of coadaptation and genetic homeostasis are considered, as well as the prospective use of the geotaxis lines to study such concepts experimentally. The geotactic behavior expressed in each line is defined as "instinctive": It increases reproductive success and is characteristic of a population.     

Dispositional and explanatory style optimism as potential moderators of the relationship between hopelessness and suicidal ideation

To test the hypothesis that higher levels of optimism reduce the association between hopelessness and suicidal ideation, 284 college students completed self-report measures of optimism and Beck scales for hopelessness, suicidal ideation, and depression. A statistically significant interaction between hopelessness and one measure of optimism was obtained, consistent with the hypothesis that optimism moderates the relationship between hopelessness and suicidal ideation. Hopelessness is not inevitably associated with suicidal ideation. Optimism may be an important moderator of the association. The development of treatments to enhance optimism may complement standard treatments to reduce suicidality that target depression and hopelessness.     

Inducing an interpretation bias changes self-imagery: a preliminary investigation

Prior work suggests that variations in self-imagery can influence the emotional interpretations people make about social situations. The current experiment investigated the converse possibility: that inducing an inferential bias can change the content of self-related images. The effects of repeated practice in accessing either negative or positive social outcomes was tested by having participants report on self-images generated during subsequent experience with ambiguous social situations. Participants and independent judges rated the content of participants’ self-images as being more negative after prior practice in accessing negative rather than positive social outcomes. Furthermore, participants who practiced accessing negative outcomes rated their anticipated anxiety in an imagined stressful social situation as being greater, and their expected social performance as poorer than participants in the positive outcome group. Groups did not differ in state anxiety levels when making their ratings, so it is unlikely that any observed differences between groups can be attributed to mood effects. We suggest that this finding is consistent with the hypothesis that inferential biases and content of self-images can interact with each other and may together serve to maintain social anxiety.