Mice: the initiation and maintenance of pregnancy-induced aggression following thelectomy

Two experiments were conducted in order to assess the effects of thelectomy (i.e., nipple removal) on the display of pregnancy-induced aggression in Rockland-Swiss (R-S) albino mice. Pregnant animals, thelectomized on Gestation Day (GD) 12, exhibit a high incidence and intensity of aggression toward adult R-S male intruders during tests conducted on GDs 14, 16, and 18 (i.e., during the last third of gestation in this species). Since thelectomized dams display levels of aggression (i.e., 63% incidence) equivalent to those of sham-operated and nonoperated animals (53 and 67% incidence, respectively), it would appear that nipple presence is not a critical factor for the maintenance of pregnancy-induced aggression in mice (Experiment 1). To examine the effects of nipple deprivation on the initiation of pregnancy-induced aggression, virgin animals were thelectomized prior to mating, then repeatedly tested for aggression at 2-day intervals of gestation. Unlike nipple-intact dams, pregnant mice, deprived of nipples prior to conception, rarely exhibit (less than 17% incidence) agonistic behaviors toward intruder males (Experiment 2). These findings suggest that the development and self-stimulation of nipples early in pregnancy may be important conditions for the display of heightened aggression with advancing pregnancy in mice.     

Predicting parental sunscreen use: Disentangling the role of action planning in the intention–behavior relationship

Structural equation modeling was used to examine antecedents of parental sunscreen use (N = 436) in a longitudinal design. The influence of a volitional planning cognition was assessed in several path models, investigating potential mediation and moderation of the intention–behavior relationship. Premotivational and motivational variables accounted for 55.1% of the variance in intention to use sunscreen. Intention emerged as the most powerful predictor of behavior, followed by action planning and self-efficacy expectations, together explaining 35.4% of parental sunscreen use after five months. Strong support was found for both mediating and moderating influences of action planning on the intention–behavior relationship. Action planning also partially mediated the impact of self-efficacy on behavior. The results support theoretical considerations to add postintentional cognitions to current health behavior models. Although action planning is an important component in the transition from intention to behavior, the impact of intention and of other premotivational and motivational variables should not be overlooked when developing health educational interventions.