Typical delay determines waiting time on periodic-food schedules: Static and dynamic tests

Pigeons and other animals soon learn to wait (pause) after food delivery on periodic-food schedules before resuming the food-rewarded response. Under most conditions the steady-state duration of the average waiting time, t, is a linear function of the typical interfood interval. We describe three experiments designed to explore the limits of this process. In all experiments, t was associated with one key color and the subsequent food delay, T, with another. In the first experiment, we compared the relation between t (waiting time) and T (food delay) under two conditions: when T was held constant, and when T was an inverse function of t. The pigeons could maximize the rate of food delivery under the first condition by setting t to a consistently short value; optimal behavior under the second condition required a linear relation with unit slope between t and T. Despite this difference in optimal policy, the pigeons in both cases showed the same linear relation, with slope less than one, between t and T. This result was confirmed in a second parametric experiment that added a third condition, in which T + t was held constant. Linear waiting appears to be an obligatory rule for pigeons. In a third experiment we arranged for a multiplicative relation between t and T (positive feedback), and produced either very short or very long waiting times as predicted by a quasi-dynamic model in which waiting time is strongly determined by the just-preceding food delay.     

Context-dependent shifts in self-regulatory personality processes during COVID-19: Changes in control predict dynamic shifts in goal reengagement capacity

The ability to reengage with new attainable goals after major setbacks is a core self-regulatory trait linked to health and well-being. Yet little is known about the extent to which such goal reengagement capacities may shift over time in response to changing contextual circumstances. Using a nationally-representative sample of U.S. adults aged 18–80 (n = 293), the present 1-year study examined whether changes in opportunity to influence life circumstances (perceived control) were coupled with dynamic shifts in goal reengagement capacity for individuals who differed in their levels of control at pandemic onset. Results from multilevel models showed that within-person increases in perceived control during the pandemic predicted corresponding within-person increases in goal reengagement capacity. Moderation models showed that the positive within-person association between perceived control and goal reengagement was pronounced for individuals with lower levels of control at pandemic onset who may be particularly sensitive to periods of opportunity to pursue new attainable goals. Findings inform theories of personality and self-regulation in pointing to contextual circumstances under which goal reengagement capacity exhibits dynamic shifts in populations who differ in their perceived opportunities for control.     

A Commodore 64-based interface system for the operant laboratory

A system of interfaces for the Commodore 64 (C-64) microcomputer for use in the operant laboratory is described. This system frees the experimenter from limitations on the number of I/O lines available on the user port of the C-64 and offers the control of operant chambers for a low cost. Subroutines in machine code to control the interfaces, offering millisecond timing of external events, are presented. A sample BASIC program demonstrates how the subroutines are called from BASIC to run a simple discrimination experiment.     

Are research subjects adequately protected? A review and discussion of studies conducted by the Advisory Committee on Human Radiation Experiments

In light of information uncovered about human radiation experiments conducted during the Cold War, an important charge for the Advisory Committee on Human Radiation Experiments was to assess the current state of protections for human research subjects. This assessment was designed to enhance the Committee's ability to make informed recommendations for the improvement of future policies and practices for the protection of research subjects. The Committee's examination of current protections revealed great improvement over those from the past, yet some problems remain. Although the data collected by the Committee highlight specific areas in need of attention, the Committee's work should be viewed in part as the beginning of a series of ongoing assessments of the adequacy and effectiveness of the protections afforded to human subjects.     

Prepulse effects on magnitude estimation of startle-eliciting stimuli and startle responses

The present studies investigated the relationship between prepulse effects on the modification of the brainstem startle reflex and magnitude estimates of startle-eliciting stimuli. In Experiment 1, startle eyeblink responses were elicited in 24 students, half of whom were instructed to estimate the loudness of the startle stimulus (actual intensities of 80, 90, and 100 dB) and half of whom were instructed to estimate the magnitude of their eyeblink. When weak acoustic prepulses preceded the startle-eliciting stimulus, eyeblink amplitude was inhibited, and estimates of response magnitude decreased, but estimates of startle stimulus magnitude decreased only when 100-dB startle stimuli were presented. In Experiment 2, the same startle stimuli were preceded on some trials by a vibrotactile prepulse to the hand. In conditions in which startle amplitude was inhibited, startle stimulus magnitude estimates were not affected. This suggests that the effect of acoustic prepulses on 100-dB startle stimuli in Experiment 1 may have been due to loudness assimilation, an effect independent of the prepulse inhibition of startle responding.