Can attention select only a fixed number of objects at a time?

Several previous studies have suggested that we may attend only a fixed number of 'objects' at a time. However, whereas findings from two-target experiments suggest that we can attend only one object at a time, other results from object-tracking and enumeration paradigms point instead to a four-object limit. Here, we note that in these previous studies the number of objects covaried with the overall size and complexity of the stimulus, such that apparent one-object or four-object limits in those tasks may reflect changes in the complexity of attended stimuli, rather than the number of objects per se. Accordingly, in the current experiments we employ stimuli in which the number of objects varies, while overall size and complexity are held constant. Using these refined measures of object-based effects, we find no evidence for a one-object or four-object limit on attention. Indeed, we conclude that the number of attended objects does not affect how efficiently we can attend a given stimulus. We propose and test an alternative approach to object-based attention limitations based on within-object and between-object feature-binding mechanisms in human vision.     

Certification change versus actual behavior change in teenage suicide rates, 1955-1979

National data on firearm suicides and accidental firearm deaths for persons aged 15-19 from 1955 to 1979 were examined to test hypotheses of increases in reported suicide rates as resulting from (1) improved accuracy in the determination and certification of suicide in equivocal firearm deaths; (2) actual increases in the rate of firearm suicides among teens; or (3) some combination of these factors. Data presented support the hypothesis of certification changes as the primary factor influencing suicide rates during the first 12-year segment, but suggest a period of actual growth combined with continued certification change from 1967 to 1979.     

Anorexia Nervosa,Major Depression,and Suicide Attempts: Shared Genetic Factors

The extent to which genetic and environmental factors influenced anorexia nervosa (AN), major depressive disorder (MDD), and suicide attempts (SA) were evaluated. Participants were 6,899 women from the Swedish Twin Study of Adults: Genes and Environment. A Cholesky decomposition assessed independent and overlapping genetic and environmental contributions to AN, MDD, and SA. Genetic factors accounted for a substantial amount of liability to all three traits; unique environmental factors accounted for most of the remaining liability. Shared genetic factors may underlie the coexpression of these traits. Results underscore the importance of assessing for signs of suicide among individuals with AN.