Biasing the pacemaker in the behavioral theory of timing

In the behavioral theory of timing, pacemaker rate is determined by overall rate of reinforcement. A two-alternative free-operant psychophysical procedure was employed to investigate whether pacemaker period was also sensitive to the differential rate of reinforcement. Responding on a left key during the first 25 s and on a right key during the second 25 s of a 50-s trial was reinforced at variable intervals, and variable-interval schedule values during the two halves of the trials were varied systematically. Responding on the right key during the first 25 s and on the left key during the second 25 s was not reinforced. Estimates of pacemaker period were derived from fits of a function predicted by the behavioral theory of timing to right-key response proportions in consecutive 5-s bins of the 50-s trial. Estimates of pacemaker period were shortest when the differential reinforcer rate most strongly favored right-key responses, and were longest when the differential reinforcer rate most strongly favored left-key responses. The results were consistent with the conclusion that pacemaker rate is influenced by relative reinforcer rate.     

Persistent crying and parenting: Search for a butterfly in a dynamic system

The risks and causes of persistent crying in early infancy are discussed on the basis of a study of 61 infants referred to the Munich Interdisciplinary Research and Intervention Program for Fussy Babies for persistent crying between 1 and 6 months of age, and of a community sample of 51 infants of the same age. Particular attention was paid to pre-verbal parent-infant communication, the development of which was interpreted in terms of a dynamic interactional system including both regulatory and communicative predispositions in infants and intuitive competence for supporting infant predispositions in parents. Neither a gut problem nor any other single causal factor was identified for persistent crying in the majority of cases. In contrast, persistent crying was significantly associated with multiple biological and psychosocial risk factors for both parents and infants. Neurological immaturity, difficult temperament and sleep problems in infants, and impaired psychological conditions, limited resources and failures of intuitive competences in mothers were found to threaten the developmental process in infants and give rise to ‘vicious circles’ which were destabilizing the interactional systems. Increased attention to intuitive parental competences is recommended as one effective model for therapeutic interventions.     

Infants' sensitivity to arbitrary object-odor pairings

The ability of 4-month-old infants to learn the arbitrary relationship between an object and a distinctive odor was assessed. Infants were familiarized with two objects while one of them was paired with a cherry odor. Results indicated that only female subjects showed evidence of matching. They increased their looking to the target object in the presence of the odor but not in the absence of the odor, relative to baseline levels.     

Communication in preterm infants: Why is it different?

The present paper selectively reviews the literature which compares full-term and preterm infants' communication with their mothers in the first year of life. The review is focused not only on what differences are found between full-term and preterm infants, but also why such differences exist. Particular emphasis is placed on the importance of interpreting the findings in the light of the developmental phase of the infants, the heterogeneity of the preterm population and the situation in which communication is studied. Most studies were not designed to consider these issues in any detail. Differences with respect to these factors can be found between studies, however, which may have contributed to the often contradictory findings. Consequently, comparisons between these studies provide clues about the effects of these factors on communicative development. The ultimate goal of this review is to point to important directions for future research on early communication in preterm infants.     

A PRELIMINARY PROCEDURE FOR PREDICTING THE POSITIVE AND NEGATIVE EFFECTS OF REINFORCEMENT-BASED PROCEDURES

In the current investigation, a modification was made to the preference assessment described by Pace, Ivancic, Edwards, Iwata, and Page (1985) to predict the effects of stimuli when used in a differential-reinforcement-of-other-behavior (DRO) schedule for 2 clients with severe self-injurious behavior (SIB) and profound mental retardation. Based on the results of the preference assessment, three types of stimuli were identified: (a) high-preference stimuli associated with high rates of SIB (HP/HS), (b) high-preference stimuli associated with relatively lower rates of SIB (HP/LS), and (c) low-preference stimuli associated with low rates of SIB (LP/LS). Consistent with the results of the preference assessment, the DRO schedule with HP/HS stimuli resulted in increased SIB, and the DRO schedule with LP/LS stimuli resulted in no changes in SIB. HP/LS stimuli were demonstrated reinforcers but did not result in a change in SIB when used in a DRO schedule. Thus, the stimulus preference assessment may be useful clinically in some situations for predicting both the beneficial and the negative side effects of stimuli in DRO procedures.     

Effects of differential reinforcement on the behavior and self-esteem of children with emotional and behavioral disorders

Students in a residential special school for children with emotional and behavioral disorders participated in a study designed to reduce their levels of inappropriate behavior. The residential care staff rated the students' behavioral problems and their class teachers rated their overt self-esteem pre and post intervention. In addition, the students completed self-ratings of their self-esteem. The students were divided into two groups, experimental and control. A multiple baseline across behaviors design was used to assess behavioral changes in the experimental group. Both groups received tangible rewards to the same level but only the experimental group received them contingent upon behaving appropriately. Results showed that the experimental group students made substantial reductions in their levels of inappropriate behavior, which were maintained at a three-month followup. Also, ratings of their behavioral problems by residential child care staff suggested that this improvement in behavior had generalized beyond the classroom to the residential setting. However, no significant differences were found between the pre- and post-intervention ratings of their self-esteem or teacher ratings of their overt self-esteem.     

From visual-motor anticipation to conceptualization: Reaction to solid and hollow objects and knowledge of the function of containment

This research investigates the development of visual-manual coordination during infancy with respect to the spatial property of concavity and the development of the capacity to expect or understand that a hollow object affords specific manual behaviors. Tumblers closed at the top by a plexiglas plate were used: They seemed to be open but resisted introduction of the hand. Infants' behavior towards these deceptive objects was compared with their behavior towards identical objects that looked and felt closed or open. The results show that from the 8th month infants exhibit to the deceptive objects an anticipatory visuomotor behavior and from ninth month they exhibit exploratory behavior that suggests that they are trying to understand the discrepancy between the objects' visual and tactile properties. It can therefore be concluded that a rudimentary conceptualization of containment appears to be elaborated by infants from ninth month.     

Effects of signaled and unsignaled shock on schedule-controlled lever pressing and schedule-induced licking: Shock intensity and body weight

Schedule-controlled lever pressing and schedule-induced licking were studied in rats under a multiple fixed-interval fixed-interval schedule of food reinforcement. Following acquisition of stable rates of pressing and licking, a multiple variable-time variable-time schedule of electric-shock delivery was superimposed upon the baseline schedule. In only one component of the multiple schedule, a 5-sec stimulus preceded each shock (signaled shock). In the other component shock was unsignaled. Several shock intensities (Experiment 1) and body weights (Experiment 2) were studied. Lever pressing and licking were affected similarly by experimental manipulations, although with parametric differences. Depending upon shock intensity and body weight, rates of lever pressing and licking were hardly suppressed, suppressed primarily in the unsignaled shock component (differential suppression), or markedly suppressed in both components. Differential suppression during components with signaled and unsignaled shock and conditioned suppression of responding during the preshock stimulus appeared not to be functionally related. Differential suppression depended more on the discriminability of shock-free time, and on shock intensity, body weight, and the type of response than on the “preparatory” behavior preceding shock.     

Essential independence and likelihood-based ability estimation for polytomous items

A definition ofessential independence is proposed for sequences of polytomous items. For items satisfying the reasonable assumption that the expected amount of credit awarded increases with examinee ability, we develop a theory ofessential unidimensionality which closely parallels that of Stout. Essentially unidimensional item sequences can be shown to have a unique (up to change-of-scale) dominant underlying trait, which can be consistently estimated by a monotone transformation of the sum of the item scores. In more general polytomous-response latent trait models (with or without ordered responses), anM-estimator based upon maximum likelihood may be shown to be consistent for under essentially unidimensional violations of local independence and a variety of monotonicity/identifiability conditions. A rigorous proof of this fact is given, and the standard error of the estimator is explored. These results suggest that ability estimation methods that rely on the summation form of the log likelihood under local independence should generally be robust under essential independence, but standard errors may vary greatly from what is usually expected, depending on the degree of departure from local independence. An index of departure from local independence is also proposed.This work was supported in part by Office of Naval Research Grant N00014-87-K-0277 and National Science Foundation Grant NSF-DMS-88-02556. The author is grateful to William F. Stout for many helpful comments, and to an anonymous reviewer for raising the questions addressed in section 2. A preliminary version of section 6 appeared in the author's Ph.D. thesis.