The startle response may interrupt information processing (interruption hypothesis), and prepulse inhibition of startle (PPI) may protect that processing from interruption (protection hypothesis). These hypotheses were tested by measuring startle eyeblinks during an Attention Network Test (ANT), a combined flanker and cue reaction time (RT) task that measures the efficiency of multiple attentional networks. ANT trials with and without startle stimuli presented in the interval between the visual cue (prepulse) and target were compared. Results showed that the startle stimulus served as an alerting stimulus, speeding RT in the ANT. However, this reaction time speeding was most pronounced on trials with no startle response (100% PPI). This suggests that the alerting effect of the startle stimulus was attenuated by the startle response, and that PPI decreased the degree of this interference, in support of the interruption and protection hypotheses.

Participant selection is an important step in research on individual differences. If detecting an effect of a personality variable is predicated on the use of extreme groups, then mistakenly including participants who are not in the extremes may weaken the ability to see an effect. In this study, changes in trait worry were evaluated in 68 undergraduate students reporting low or high levels of worry. Participants completed the abbreviated Penn State Worry Questionnaire (PSWQ-A) three times: 1) at the beginning of the semester; 2) 3 -13 weeks later; and 3) 1 hr later, following a psychophysiological assessment session. Test-retest reliability across the three administrations was high, but almost half of the sample no longer met the pre-defined criteria for classification as low or high worriers at the second administration. That is, scores were reliable, but not stable, across time. Instability of self-report worry was significantly greater for high worriers than for low worriers, and this effect was predicted by trait anxiety at the beginning of the semester. These findings suggest that the PSWQ-A is sensitive to factors other than trait worry, which may result in dilution of effects when participants are selected for extreme worry scores. This also suggests that screening participants weeks before the actual study should be supplemented by readministration of the screening questionnaire, to identify participants who no longer meet criteria for inclusion.