The extent of active processing of a long-duration stimulus modulates the scalp-recorded sustained potential

A long-duration stimulus will elicit a negative sustained potential (SP) that is maximum in amplitude over fronto-central areas of the scalp. This study examines how the duration of active attentional processing of the stimulus might also elicit a nonsensory contingent negative variation (CNV) that overlaps and summates to the SP. Subjects were presented with either a low- or high-pitched 1.4s duration stimulus. In different conditions, a 20 ms gap occurred either 300 or 1300 ms after stimulus onset in half the stimuli. The subject's task was to button press upon detection of the gap in the low-pitched stimulus. The subject was not required to respond to the gap occurring in the high-pitched tone. In a separate Ignore condition, subjects ignored all stimuli and read a book. In the Ignore condition, a SP was apparent to the long-duration stimuli. In the Attend condition, a large amplitude slow wave, probably the CNV, overlapped and summated with the SP. The extent of the overlapping CNV was dependent on whether the gap occurred early or late. The CNV was not apparent following presentation of the high-pitched tone, when the gap did not need to be detected. Consistent with previous studies, a SP was thus elicited even when active processing of the stimulus was not required. The morphology of the scalp-recorded SP was, nevertheless, much modified by an overlapping and summating CNV, depending on the extent to which active processing of the long-duration stimulus was required.     

Cradling side preference is associated with lateralized processing of baby facial expressions in females

Women’s cradling side preference has been related to contralateral hemispheric specialization of processing emotional signals; but not of processing baby’s facial expression. Therefore, 46 nulliparous female volunteers were characterized as left or non-left holders (HG) during a doll holding task. During a signal detection task they were then asked to detect the emotional baby faces in a series of baby portraits with neutral and emotional facial expressions, presented either to the left or the right visual field (VFP). ANOVA revealed a significant HG × VFP interaction on response bias data (p < .05). Response bias was lowest when emotional baby faces were presented in the visual field of cradling side preference, suggesting that women’s cradling side preference may have evolved to save cognitive resources during monitoring emotional baby face signals.     

Duration comparison: relative stimulus differences stimulus age, and stimulus predictiveness.

Under a psychophysical trials procedure, pigeons were presented with a red light of one duration followed by a green light of a second duration. Eight geometrically spaced base durations were paired with one of four shorter and four longer durations as the alternate member of a duration pair, with different pairs randomly intermixed. One choice was reinforced if red had lasted longer than green, and a second choice was reinforced if green had lasted longer. Performance was compared when all the base durations and their pair members were included (entire-range condition) or when only the four longest base durations and their comparison durations (restricted-range condition) were used. Discrimination sensitivity decreased for longer duration pairs under both conditions, supporting a memory-based account. Sensitivity was lower under the restricted-range condition. Under both conditions, a bias to report "green as longer" increased as the second green duration increased. Bias changed as a matching function of the green-duration predictiveness of the correct choice. The results are related to a quantitative model of timing and remembering proposed by Staddon.     

Education and testing strategy for large-scale cystic fibrosis carrier screening

Population-based screening for cystic fibrosis carrier mutations presents a number of challenges for genetic counselors, owing primarily to the inability of current DNA testing technology to identify all possible mutations and the difficulty involved in conveying the concept of residual risk to those patients who test negative. To address these issues, we are conducting a pilot study, as part of a consortium established by the National Center for Human Genome Research, to explore the efficacy, acceptance, and psychosocial impact of various approaches to carrier screening in an ethnically diverse Southern California population. This article reports the patient instructional and screening strategies we developed in the initial phase of the project in order to optimize our chances of answering these questions and delivering this service on a large scale.     

Signal detection and matching: analyzing choice on concurrent variable-interval schedules.

Pigeons' pecks on a red key and a green key were followed by access to grain according to pairs of concurrent independent variable-interval schedules in a combined signal detection/matching law paradigm. Pecks on the red key were reinforced by the richer variable-interval schedule if a short-duration tone had been presented; pecks on the green key were reinforced by the richer variable-interval schedule if a long-duration tone had been presented. Pecks on the green key given a short-duration tone, or on the red key given a long-duration tone, were reinforced by the leaner variable-interval schedule. The data were analyzed according to both signal detection's and the matching law's separate measures of, first, the discrimination of the choices and, second, the bias to make one response or another. Increasing the difficulty of the tone-duration discrimination decreased both methods' measures of the discrimination of the choices and did not change both methods' measures of the bias to make one response or another. Changing the leaner variable-interval schedule so that it approached the richer variable-interval schedule decreased signal detection's measure of discrimination but left its measure of response bias and the matching law measures unchanged. Data collected only until a subject's first changeover response following presentation of a long or a short tone showed higher values for both methods' measures of discrimination, no change in signal detection's measure of response bias, and lower values for the matching law's measure of response bias. Relationships between the matching law's and signal detection's methods of analyzing choice are discussed. It is concluded that a signal detection analysis is more efficient for examining changes in the difficulty of a discrimination, whereas a matching law analysis is more effective for examining the effects of changes in relative reinforcer frequency.     

The excitatory state in the triangular constant method

The Triangular Constant Method was designed for the measurement of discriminability between sensory stimuli. Its original model assumes a steady excitatory detection state. The purpose of this paper is to elaborate on the consequences of assuming a variable excitatory state and to formulate the concomitant model.     

Stimuli, reinforcers, and behavior: an integration

We propose that a fundamental unit of behavior is the concurrent discriminated operant, and we discuss in detail a quantitative model of the concurrent three-term contingency that is based on the notion that an animal's behavior is controlled to differing extents by both stimulus—behavior and behavior—reinforcer relations. We show how this model can describe performance in a variety of experimental procedures: conditional discrimination and matching to sample, both with and without reinforcement for responses that are traditionally identified as errors; conditional discrimination with more than two stimuli and choice alternatives; delayed matching to sample and delayed reinforcement in matching to sample; second-order and complex conditional discrimination; and multiple and concurrent schedules. Although the model is incomplete in its coverage, and may be incorrect, we believe that this conceptual approach will bear fruit in the development of behavior theory.     

Effects of varying stimulus disparity and the reinforcer ratio in concurrent-schedule and signal-detection procedures.

The present study measured the effects of stimulus and reinforcer variations on pigeons' behavior in two different choice procedures. Two intensities of white light were presented as the stimuli on the main key in a switching-key concurrent schedule and as the sample stimuli in a signal-detection procedure. Under both procedures, the scheduled rate of reinforcement was varied across conditions to produce various ratios of obtained reinforcement. These ratios were obtained for seven pairs of light intensities. In the concurrent schedules, the effects of reinforcer-ratio variations were positively correlated with the physical disparity between the two light intensities. In the signal-detection procedure, changes in the reinforcer ratio produced greater effects on performance when stimulus disparity was very low or very high compared to those found at intermediate levels of stimulus disparity. This discrepancy creates a dilemma for existing behavioral models of signal-detection performance.