Adaptation to auditory motion in the horizontal plane: Effect of prior exposure to motion on motion detectability

Thresholds for auditory motion detectability were measured in a darkened anechoic chamber while subjects were adapted to horizontally moving sound saurces of various-velocities. All stimuli were 500-Hz lowpass noises presented at a level of 55 dBA. The threshold measure employed was the minimum audible movement angle(MAMA)—that is, the minimum angle a horizontally moving sound must traverse to be just discriminable from a stationary sound. In an adaptive, two-interval forced-choice procedure, trials occurred every 2-5 sec (Experiment 1) or every 10–12 sec (Experiment 2). Intertrial time was “filled” with exposure to the adaptor—a stimulus that repeatedly traversed the subject’s front hemifield at ear level (distance: 1.7 m) at a constant velocity (?150°/secto + 150°/sec)during a run. Average MAMAs in the control condition, in which the adaptor was stationary (0°/sec), were 2.4° (Experiment 1) and 3.0° (Experiment 2). Three out of 4 subjects in each experiment showed significantly elevated MAMAs (by up to 60%), with some adaptors relative to the control condition. However, there were large intersubject differences in the shape of the MAMA versus adaptor velocity functions. This loss of sensitivity to motion that most subjects show after exposure to moving signals is probably one component underlying the auditory motion aftereffect (Grantham, 1989), in which judgmentsof the direction-afmoving sounds are biased in the direction opposite to that of a previously presented adaptor.     

Broken-Backed Naturalism

Willem Drees's stated purpose in Religion, Science and Naturalism is to maintain the continuing importance of religion in human life while being honest to the sciences. His preferred way of doing that is an example of what John Dewey once called "broken-backed naturalism." In contrast, Deweyan humanism accomplishes Drees's purpose in a more thoroughly naturalistic way. It does not bifurcate the world into the domain of the sciences—the natural world—and the domain of religion—the provider of answers to limit questions about the world as a whole, which fall outside the scope of the sciences.     

A decision tree approach to selecting an appropriate observation reliability index

Based on the conceptual framework outlined by Cone (1986) and Suen (1988), a practical decision tree is developed as an aid for the selection of observational reliability indices.     

Discrimination by olfactory cues in albino rats reflecting familiarity and relatedness among conspecifics

The present investigation sought to determine whether albino rat pups could discriminate among familiar siblings, nonfamiliar siblings, familiar nonsiblings (foster littermates), and nonfamiliar nonsiblings (unrelated agemates) using only olfactory cues. Pairing all possible combinations of familiarity and kinship variables (six), the odors were presented in paired combinations to each of twelve experimental subjects. Results from dependent t tests indicated that the albino rat pups could discriminate between the following pairs of odors using only the olfactory sensory modality: (a) familial siblings and nonfamiliar siblings, (t = 3.41, p = .006); (b) familiar siblings and nonfamiliar nonsiblings, (t = 9.62, p = .001); (c) nonfamiliar siblings and nonfamiliar nonsiblings, (t = 3.15, p = .009); and (d) familiar nonsiblings and nonfamiliar nonsiblings (t = 2.58, p = .026).     

Partial reinforcement effects in instrumental escape conditioning

In Experiment I acquisition and extinction of instrumental escape conditioning with rats (N = 64) were studied as a function of reinforcement magnitude under conditions of partial and continuous reinforcement. In Experiment II the effects of partial and continuous reinforcement were studied in rats (N = 96) during acquisition followed by small, medium, and large reductions in reinforcement magnitude. A water-tank escape apparatus was used with temperature as the relevant variable. It was found that (1) with large reinforcement magnitude a continuously reinforced group was superior in acquisition to one that was partially reinforced; there were no differences with small reinforcement; (2) disruptive effects of a nonreinforced trial (a) appear early in learning, (b) are quite strong after each nonreinforced trial, and (c) persist through several succeeding reinforced trials; (3) major competing behaviors persist throughout acquisition for small reinforcement magnitude regardless of schedule, decline with large reinforcement (more so with continuous than with partial), and return to a high level in extinction for all conditions; (4) the partial reinforcement extinction effect occurs after large reinforcement but not after small, and it appears only with large reductions in reinforcement magnitude which approach extinction conditions. Only the first part of the last finding appears to be consistent with the appetitive conditioning literature.     

Reminder-induced recovery of associations to an overshadowed stimulus

The possibility of reversing the deficit produced by overshadowing through the use of memory reactivation was investigated. Using lick suppression as a measure of associative strength, water-deprived rats were conditioned in a Pavlovian paradigm which produced reliable overshadowing of a flashing light by a tone. It was found, however, that exposure to the overshadowed stimulus outside of the conditioning context during the retention interval (reminder treatment) caused an increase in lick suppression during testing in animals that had undergone overshadowing, relative to nonreminded overshadowed animals. Subjects that received the reminder treatment but were conditioned without overshadowing showed no increase in lick suppression. Additional control groups ensured that the increase in suppression observed in the overshadowed subjects following reminder treatment was not due to nonspecific fear. The results suggest that the performance deficit produced by overshadowing is due at least in part to a reversible failure to efficiently retrieve associations to the overshadowed stimulus at the time of testing, rather than a failure to form those associations during conditioning.