Stability,breadth and guidance

Much recent work on explanation in the interventionist tradition emphasizes the explanatory value of stable causal generalizations—i.e., causal generalizations that remain true in a wide range of background circumstances. We argue that two separate explanatory virtues are lumped together under the heading of `stability’. We call these two virtues breadth and guidance respectively. In our view, these two virtues are importantly distinct, but this fact is neglected or at least under-appreciated in the literature on stability. We argue that an adequate theory of explanatory goodness should recognize breadth and guidance as distinct virtues, as breadth and guidance track different ideals of explanation, satisfy different cognitive and pragmatic ends, and play different theoretical roles in (for example) helping us understand the explanatory value of mechanisms. Thus keeping track of the distinction between these two forms of stability yields a more accurate and perspicuous picture of the role that stability considerations play in explanation.     

Backward visual masking in children and adolescents: sensory transmission, accrual rate and asymptotic performance.

We have applied the Lagged Accrual Model of visual backward masking to a group of children (aged 10) and a group of adolescents (aged 15). The two groups did not differ on sensory transmission time, indicating that the speed of sensory transmission has already attained its maximum by age 10. The older group showed a significantly greater rate of information accrual and a greater amount of information extraction. An application of the model to previously published data revealed that very young children (aged 5) have slower sensory transmission times.     

Hedonic capacity and schizotypy revisited: a taxometric analysis of social anhedonia

P. E. Meehl (1962) originally conjectured that hedonic capacity was an indicator of the latent class or taxon of schizotypy. However, P. E. Meehl (1989, 1990) subsequently diminished the role of hedonic capacity in his theory, indicating that hypohedonia is one of a dozen normal-range (nontaxonic) individual-differences factors that may potentiate the expression of schizophrenia. This dimensional-only view of hedonic capacity was tested by applying taxometric procedures to the Revised Social Anhedonia Scale (RSAS; M. L. Eckblad, L. J. Chapman, J. P. Chapman, & M. Mishlove, 1982) in a sample of college students (N = 1,526). Analyses indicated that the construct measured by the RSAS is taxonic in nature with a base rate approximating .10. These data are interpreted in the context of other findings suggesting that social anhedonia is an indicator of schizotypy.     

Posttraumatic stress and depressive symptoms in a college population one year after the September 11 attacks: the effect of proximity

As a follow-up to our earlier report [Behav. Res. Ther., in press] on the level of posttraumatic stress symptoms (PTSS), depressive symptoms, and frequency of diagnoses of probable posttraumatic stress disorder (PTSD) among college students at three public universities (Albany, NY, Augusta, GA, and Fargo, ND) resulting from the September 11, 2001. Terrorist attacks, we surveyed comparable groups of students (total, n = 1313) from these three institutions in the weeks following the first anniversary (2002) of the attacks. We found proximity effects (Albany higher than Augusta which was higher than Fargo) for PTSS and depressive symptoms but not for frequency of diagnoses of probable PTSD. Within the Albany site data, proximity of county of residence to New York City (NYC) also showed a proximity effect on PTSS. Although depressive symptoms were significantly different in 2002 versus 2001, the arithmetic differences in PTSS or in frequency of diagnoses of probable PTSD were not significant. The September 11 attacks continued to exert a psychic toll on college students even a year later.     

Defensive behaviors in rats following septal and septal--amygdala lesions

Rats with anterior septal lesions showed a pattern of consistent enhancement of defensive behaviors normally elicited by threatening conspecifics, with no enhancement of attack or general reactivity. Further division of this group indicated that damage to sites anterior and ventral to the septal area, sites previously implicated in the "septal syndrome," produces maximal effect on these behaviors. When amygdala lesions are combined with septal damage this enhanced defensive responding is almost completely eliminated. These results were interpreted as indicating that the septal syndrome represents hyperdefensiveness to conspecific threat stimuli rather than aggression or increased general reactivity, and that amygdaloid mechanisms are also involved in the regulation of conspecific defensive behaviors.