Behavioral variability in an evolutionary theory of behavior dynamics

McDowell’s evolutionary theory of behavior dynamics (McDowell, 2004) instantiates populations of behaviors (abstractly represented by integers) that evolve under the selection pressure of the environment in the form of positive reinforcement. Each generation gives rise to the next via low‐level Darwinian processes of selection, recombination, and mutation. The emergent patterns can be analyzed and compared to those produced by biological organisms. The purpose of this project was to explore the effects of high mutation rates on behavioral variability in environments that arranged different reinforcer rates and magnitudes. Behavioral variability increased with the rate of mutation. High reinforcer rates and magnitudes reduced these effects; low reinforcer rates and magnitudes augmented them. These results are in agreement with live‐organism research on behavioral variability. Various combinations of mutation rates, reinforcer rates, and reinforcer magnitudes produced similar high‐level outcomes (equifinality). These findings suggest that the independent variables that describe an experimental condition interact; that is, they do not influence behavior independently. These conclusions have implications for the interpretation of high levels of variability, mathematical undermatching, and the matching theory. The last part of the discussion centers on a potential biological counterpart for the rate of mutation, namely spontaneous fluctuations in the brain's default mode network.     

Evaluating the efficacy of the Headsprout© reading program with children who have spent time in care

This study investigated whether Headsprout©, an internet‐based phonics program designed on behavioral principles, is an effective supplementary tool to improve literacy skills of children who have spent time in care and are at risk of reading failure. Participants were 8 children (aged 5 to 10) who had spent over 3 years in care and were fully adopted at the time of the study. Participants' literacy skills were assessed prior to intervention using 2 standardized reading attainment tests. Participants were then randomly assigned to either treatment or a waiting list comparison group. There were 2 Headsprout© treatments, but all participants in the treatment group completed 1 HeadsproutStartCopTextStartCopText© lesson 4 times per week, under the supervision of the first author, while participants in the comparison group interacted with the first author 4 times per week engaging in nonliteracy‐based computer activities. Results from 2 standardized reading attainment tests showed an improvement in word recognition age and oral reading fluency for the HeadsproutStartCopTextStartCopText© learners but scores either remained the same or decreased over a 4‐month period for participants in the comparison group. The findings support the wider use of HeadsproutStartCopTextStartCopText© with at‐risk children though more research is clearly warranted at this time.     

A COMPUTATIONAL THEORY OF SELECTION BY CONSEQUENCES APPLIED TO CONCURRENT SCHEDULES

Virtual organisms animated by a computational theory of selection by consequences responded on symmetrical and asymmetrical concurrent schedules of reinforcement. The theory instantiated Darwinian principles of selection, reproduction, and mutation such that a population of potential behaviors evolved under the selection pressure exerted by reinforcement from the environment. The virtual organisms' steady‐state behavior was well described by the power function matching equation, and the parameters of the equation behaved in ways that were consistent with findings from experiments with live organisms. Together with previous research on single‐alternative schedules (McDowell, 2004; McDowell & Caron, 2007) these results indicate that the equations of matching theory are emergent properties of the evolutionary dynamics of selection by consequences.     

Much Ado about Nothing: Karl Barth's Being Unable to Do Nothing about Nothingness

Often a source of concern to commentators about the adequacy of Barth's theology is his treatment of evil, in particular Church Dogmatics III/3 §50 with its depiction of evil as das Nichtige (the nothingness). Against the impression that Barth has little time in his systematic theology for doing justice to evil it is worth attempting a reading that indicates the importance of this section and what it seems that Barth is doing with it. Das Nichtige belongs to a conflictual and dramatic account, and talk of its, for Barth, 'absurd'existence' belongs there. The dramatic flavour of this discussion further impresses that there is more to be said about 'Barth on evil' than any focus on the paradoxical and negative language used to depict it could express – this 'more' should come specifically through ethics.     

Falsification of matching theory: changes in the asymptote of Herrnstein''s hyperbola as a function of water deprivation.

Five rats pressed levers on variable-interval schedules of water reinforcement at various levels of water deprivation. In one phase of the experiment, three deprivation conditions that replicated conditions in Heyman and Monaghan (1987) were arranged, along with three less extreme deprivation conditions. In a second phase, water deprivation was arranged so that subjects were exposed to a greater range of access to water per day. Herrnstein's hyperbola described the rats' response-rate data well. The y asymptote, k, of the hyperbola appeared roughly constant over the conditions that replicated those of Heyman and Monaghan, but decreased markedly when less extreme deprivation conditions were included. In addition, k varied systematically when the second method of arranging deprivation was used. These results falsify a strong form of matching theory and confirm predictions made by linear system theory.