Amplitude and Width Manipulations in Fitts' Paradigm: Comment on Heath et al. (2011) and Heath et al. (2016)

Heath, Weiler, Marriott, Elliott, and Binstead (2011 Heath, M., Weiler, J., Marriott, K. A., Elliott, D., &; Binstead, G. (2011). Revisiting Fitts and Peterson (1964): Width and Amplitude manipulations to the reaching environment elicit dissociable movement times. Canadian Journal of Experimental Psychology, 65, 259–268.1.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]) and Heath, Samani, Tremblay, and Elliott (2016 Heath, M., Samani, A., Tremblay, L., &; Elliott, D. (2016). Fitts' theorem in oculomotor control: Dissociable movement times for amplitude and width manipulations. Journal of Motor Behavior, 48, 489–499.[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]) have claimed that there are dissociable movement times for amplitude and width manipulations in the Fitts' paradigm. This may to some extent be true, but the Heath et al. (2011 Heath, M., Weiler, J., Marriott, K. A., Elliott, D., &; Binstead, G. (2011). Revisiting Fitts and Peterson (1964): Width and Amplitude manipulations to the reaching environment elicit dissociable movement times. Canadian Journal of Experimental Psychology, 65, 259–268.1.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]) and Heath et al. (2016 Heath, M., Samani, A., Tremblay, L., &; Elliott, D. (2016). Fitts' theorem in oculomotor control: Dissociable movement times for amplitude and width manipulations. Journal of Motor Behavior, 48, 489–499.[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]) data do not support that contention, as shown in this comment. It is shown that data from the research of Heath et al. is not in the range of index of difficulty where ongoing visual control would be used and hence their fits of data to Fitts' law are spurious. The data of Heath et al. (2011 Heath, M., Weiler, J., Marriott, K. A., Elliott, D., &; Binstead, G. (2011). Revisiting Fitts and Peterson (1964): Width and Amplitude manipulations to the reaching environment elicit dissociable movement times. Canadian Journal of Experimental Psychology, 65, 259–268.1.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]) for arm movements and for the primary eye saccade submovements of Heath et al. (2016 Heath, M., Samani, A., Tremblay, L., &; Elliott, D. (2016). Fitts' theorem in oculomotor control: Dissociable movement times for amplitude and width manipulations. Journal of Motor Behavior, 48, 489–499.[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]) are well correlated by the ballistic movement time equation of Hoffmann (1981 Hoffmann, E. R. (1981). An ergonomic approach to predetermined motion time systems. Proceedings of the 9th National Conference of the Institute of Industrial Engineers, Australia, 30–47. [Google Scholar]) and Gan and Hoffmann (1988 Gan, K.-C. &; Hoffmann, E. R. (1988). Geometrical conditions for ballistic and visually controlled movements. Ergonomics, 31, 829–839.[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]). When the ballistic equation is used to model data for constant amplitude and constant target width conditions, the effects of the amplitude and width manipulations disappear. Other research indicates that the independent effects of movement amplitude occur due to changes in the time for the distance-covering phase of the movement.     

Reinforcing effects of caffeine in coffee and capsules.

In a residential research ward the reinforcing and subjective effects of caffeine were studied under double-blind conditions in volunteer subjects with histories of heavy coffee drinking. In Experiment 1, 6 subjects had 13 opportunities each day to self-administer either a caffeine (100 mg) or a placebo capsule for periods of 14 to 61 days. All subjects developed a clear preference for caffeine, with intake of caffeine becoming relatively stable after preference had been attained. Preference for caffeine was demonstrated whether or not preference testing was preceded by a period of 10 to 37 days of caffeine abstinence, suggesting that a recent history of heavy caffeine intake (tolerance/dependence) was not a necessary condition for caffeine to function as a reinforcer. In Experiment 2, 6 subjects had 10 opportunities each day to self-administer a cup of coffee or (on different days) a capsule, dependent upon completing a work requirement that progressively increased and then decreased over days. Each day, one of four conditions was studied: caffeinated coffee (100 mg/cup), decaffeinated coffee, caffeine capsules (100 mg/capsule), or placebo capsules. Caffeinated coffee maintained the most self-administration, significantly higher than decaffeinated coffee and placebo capsules but not different from caffeine capsules. Both decaffeinated coffee and caffeine capsules were significantly higher than placebo capsules but not different from each other. In both experiments, subject ratings of "linking" of coffee or capsules covaried with the self-administration measures. These experiments provide the clearest demonstrations to date of the reinforcing effects of caffeine in capsules and in coffee.     

Oral self-administration of pentobarbital by rhesus monkeys: relative reinforcing effects under concurrent fixed-ratio schedules.

During daily 3-hr sessions, orally delivered pentobarbital solutions and water, or two separate pentobarbital solutions, were concurrently available to rhesus monkeys according to fixed-ratio schedules of mouth contacts with a spout. First water, and then each of four "comparison-concentration" pentobarbital solutions (0.0625, 0.25, 1, and 4 mg/mL), was successively available from one spout for a block of sessions under a fixed-ratio-64 (three monkeys) or fixed-ratio-16 (one monkey) schedule. Under an identically sized fixed-ratio schedule, deliveries of a "standard-concentration" pentobarbital solution were concurrently available from a second spout. The concentration of the standard solution remained unchanged throughout testing of the series of comparison solutions. Each of three pentobarbital concentrations (4, 1, and 0.25 mg/mL) in turn served as the standard concentration. Within each pair of concurrently available solutions, the higher drug concentration maintained more behavior than the lower concentration. Thus when monkeys were provided with concurrent access to different pentobarbital concentrations, relative reinforcing effects were directly related to drug concentration. Further, the amount of behavior maintained by a particular drug concentration was dependent on the concentration of the concurrently available drug solution. Thus, the relative effectiveness of a reinforcer in maintaining behavior is a function of both the reinforcer's magnitude and the availability of alternative reinforcers in the environment.     

A rasch model for continuous ratings

A unidimensional latent trait model for continuous ratings is developed. This model is an extension of Andrich's rating formulation which assumes that the response process at latent thresholds is governed by the dichotomous Rasch model. Item characteristic functions and information functions are used to illustrate that the model takes ceiling and floor effects into account. Both the dichotomous Rasch model and a linear model with normally distributed error can be derived as limiting cases. The separability of the structural and incidental parameters is demonstrated and a procedure for estimating the parameters is outlined.     

EFFECTS AND SIDE EFFECTS OF DRO AS TREATMENT FOR SELF-INJURIOUS BEHAVIOR

A three-part controlled case study is presented in which severe and longstanding self-injurious behavior exhibited by a 9-year-old-boy was treated successfully with differential reinforcement of other behavior. In Phase 1, an experimental analysis demonstrated that the boy's scratching was not maintained by environmental contingencies; instead, it appeared that the self-injurious behavior was a stereotypic (automatically reinforced) response. In Phase 2, the effects of an escalating differential-reinforcement-of-other-behavior schedule mediated through token reinforcement (pennies) were evaluated in a reversal design. Results showed that differential-reinforcement-of-other-behavior eliminated self-injurious behavior very quickly and for periods of time as long as 30 min. A noteworthy side effect observed during Phase 2 was the occurrence of crying behavior following the nondelivery of reinforcement. In Phase 3, the token program was gradually extended in 30-min increments throughout the day. Additionally, results of a brief multielement manipulation showed that the effects of token reinforcement were superior to those of a more easily administered differential reinforcement of other behavior based on social reinforcement, which differed little from baseline.     

Issues associated with repeated neuropsychological assessments

Distinguishing practice effects from other factors in repeated neuropsychological assessments are discussed in the context of research studies and clinical/forensic assessments. Potential methodological procedures for reducing the impact of practice effects in research settings are outlined. In contrast, the potential clinical utility and interpretation of practice effects in clinical assessments and forensic evaluations are highlighted.