On the role of covarying functions in stimulus class formation and transfer of function

This experiment investigated whether directly trained covarying functions are necessary for stimulus class formation and transfer of function in humans. Initial class training was designed to establish two respondent-based stimulus classes by pairing two visual stimuli with shock and two other visual stimuli with no shock. Next, two operant discrimination functions were trained to one stimulus of each putative class. The no-shock group received the same training and testing in all phases, except no stimuli were ever paired with shock. The data indicated that skin conductance response conditioning did not occur for the shock groups or for the no-shock group. Tests showed transfer of the established discriminative functions, however, only for the shock groups, indicating the formation of two stimulus classes only for those participants who received respondent class training. The results suggest that transfer of function does not depend on first covarying the stimulus class functions.     

Training staff to conduct a paired-stimulus preference assessment

Three staff members were trained to conduct stimulus preference assessments using a paired-stimulus format with 8 children with autism. Staff were trained to mastery level using brief instruction, a video model, and rehearsal with verbal feedback. Training took about 80 min per staff member. Results demonstrated that staff rapidly learned to correctly perform paired-stimulus preference assessments with children.     

Assessing object-to-picture and picture-to-object matching as prerequisite skills for pictorial preference assessments

Tangible and pictorial paired-stimulus (PPS) preference assessments were compared for 6 individuals with developmental disabilities. During tangible and PPS assessments, two edible items or photographs were presented on each trial, respectively, and approach responses were recorded. Both assessments yielded similar preference hierarchies for 3 participants who could match pictures and objects but different hierarchies for 3 participants who could not. Reinforcer assessments verified that items identified as high preference on PPS assessments functioned as reinforcers only for participants with matching skills.     

Speed contingencies, number of stimulus presentations, and the nodality effect in equivalence class formation.

Two experiments compared performances on conditional discrimination tasks using single-participant designs with and without speed contingencies. Experiment 1 was a systematic replication of Spencer and Chase (1996). Experiment 2 presented equal numbers of training and testing trials. In each experiment, 2 female undergraduates participated. Each formed three five-member and three seven-member equivalence classes in Experiments 1 and 2, respectively. Response speed was an inverse function of nodal number and relational type in Experiment 1, but only of relational type (i.e., baseline, symmetry, transitivity, and equivalence) in Experiment 2, with and without the speed contingency. Accuracy tended to peak without the speed contingency in both experiments. Adding the speed contingency increased response speeds in both experiments, more so in Experiment 2 with a lower limited hold for I participant. The results of Experiment 2 cast doubt on previous reports of the nodality effect and on the notion of "relatedness" among class members, and they support a reinforcement-contingency, rather than a structural, account of equivalence class formation.     

Rapid acquisition of preference in concurrent chains

We report two experiments using a concurrent-chains procedure in which one terminal-link schedule was fixed-interval 8 s and the alternative schedule changed randomly from day to day. In Experiment 1, the alternative schedule varied between 4 s and 16 s according to a pseudorandom binary sequence similar to the one used by Hunter and Davison (1985). Similar to results with concurrent schedules, pigeons' response allocation in the initial link was most sensitive to the schedules arranged in the current session, although some effect of prior history was evident. Overall sensitivity was lower than for comparable data from steady-state research. In Experiment 2, a unique value between 2 s and 32 s was used for the alternative-schedule delay in each session. Sensitivity levels were similar to Experiment 1 and remained unchanged across 61 sessions of training. For all subjects, sensitivity was greater when the alternative-schedule delay was greater than 8 s compared with when it was less than 8 s. Generalized-matching plots revealed evidence of clustering of data points into two groups for some pigeons, suggesting that a process similar to a categorical discrimination may have at least partly determined response allocation. Overall, this research shows that pigeons' initial-link response allocation can adjust rapidly to frequent changes in the terminal links.     

Stimulus generalization of behavioral history

Undergraduates responded under a variable-ratio 30 schedule in the presence of a 25-mm long line and on a differential-reinforcement-of-low-rate 6-s schedule when a 13-mm long line was present. Following this, a line-length continuum generalization test was administered under a fixed-interval 6-s schedule (Experiment 1) or extinction (Experiment 2). In both experiments, obtained generalization gradients conformed to typical postdiscrimination gradients. Responses were frequent under stimuli physically similar to the 25-mm line and infrequent under stimuli physically similar to the 13-mm line. The generalization gradients were generally asymmetric with peak response rates occurring at line lengths greater than 25 mm.     

An analysis of generalized contextual control of conditional discriminations

This research asked whether performance engendered by contextual control procedures would generalize to novel matching-to-sample stimulus arrangements. Two studies were conducted with young adult participants. In Study 1, participants first were trained to perform the contextually controlled conditional discrimination, X-AB, where the sample-comparison relations A1B1 and A2B2 were reinforced in the presence of contextual stimulus X1, but the relations A1B2 and A2B1 were reinforced in the presence of X2. Then, a new conditional discrimination, CD, was established via an unreinforced-conditional-selection procedure. Next, participants were tested for X-CD contextual control performance. Participants selected the originally established CD relations in the presence of X1, but the opposite relations in the presence of X2. Next, an additional conditional relation, EF, was established. Then, participants received trials consisting of entirely novel contextual stimuli, Z1 and Z2, and EF samples and comparisons. Selections were consistent with contextual control; that is, participants selected the originally established EF relations in the presence of one of the novel contextual Z stimuli, but selected the opposite EF relations in the presence of the other contextual Z stimulus. Study 2 systematically replicated these results with naive participants and demonstrated the necessity of first establishing a conditional discrimination prior to tests for generalized contextual control. The findings are discussed in terms of unreinforced conditional selection, stimulus classes, and new ways in which contextual control performances can emerge.     

Preference reversals with food and water reinforcers in rats

Rats were given a choice between a smaller, immediately available reward and a larger reward available after a delay. In one phase, the reward was food and in another phase, the reward was water. Constant delays were added between the choice presentation and the delivery of the reward alternatives. As the time between choice and reward delivery increased from 0 to 25 s, all rats (except one in the water phase) reversed their preference from the smaller, sooner alternative to the larger, later alternative. These findings extend the generality of the preference-reversal animal model to qualitatively different reinforcers. Furthermore, the presence of both impulsive and self-control choices within the same animal is consistent with the view that self-control may be understood as choice behavior, and that species differences in self-control may be differences in degree, not kind.     

Parent treatment of complex pica in a teen with autism

Pica is a severe behavior disorder involving the persistent consumption of nonnutritive substances. Due to health complications and risks for fatality, designing effective behavioral treatments that are feasible for implementation by family members at home is imperative. This case report presents a parent-conducted functional analysis and treatment evaluation of automatically maintained pica in a teenager with autism spectrum disorder. Initial treatment with a competing stimulus was effective when paired with response interruption and redirection. Although effective, this combination of treatment components required very close parental proximity and led to increases in untargeted body-oriented pica (e.g., ingestion of skin, hair, and nails). Upon extending treatment to include the second topography of pica, both the originally targeted (object-oriented) pica and body-oriented pica decreased. Nonetheless, treatment effects were not sustained while fading parent proximity. The treatment was then augmented a third time with response cost. This final treatment package produced clinically significant reductions in all pica, facilitated parent proximity fading until the participant was alone, extended to their home, and maintained over a year of follow up.     

Interpersonal consequences of joint food consumption for connection and conflict

For centuries, the preparation and eating of a meal has brought people together, making food consumption an inherently social process. Yet the way in which people connect over food is changing. Rising health concerns, due in part to the increase in food allergies and obesity, have shifted attention away from the social aspects of food to food's nutritional aspects. Recognizing the social context in which food consumption takes place, this article reviews research highlighting the interpersonal consequences of joint food consumption. We first examine research on how sharing food connects people together, both via the type of food consumed (e.g., incidental food similarity) and the manner in which people serve and eat food (e.g., from shared vs. separate plates). We then turn to research that addresses the opposite side of the coin, discussing how the inability to share in a meal can be isolating, as well as how people navigate conflicting preferences when making food decisions with others. We conclude with a discussion of promising future directions for research on joint food consumption.