Presession attention affects the acquisition of tacts and intraverbals

This study examined the effects of presession attention on the acquisition of tacts (Experiment 1) and intraverbals (Experiment 2) in children diagnosed with autism. Each participant experienced 3 conditions. In the first 2 conditions, participants experienced a 15-min interval of either presession attention (PA) or no presession attention (NPA) followed by a teaching session. The third condition was a control condition. Across experiments, all participants acquired the verbal operants assigned to the NPA condition, whereas only 4 of the 6 participants acquired the verbal operants assigned to the PA condition. Five of the 6 participants required fewer sessions to meet the mastery criterion and a shorter duration of training for the verbal operants assigned to the NPA condition as compared to the PA condition. These outcomes suggest that antecedent manipulations traditionally reserved for mand training can positively affect the acquisition of other verbal operants. Theoretical implications are discussed.     

Discrimination thresholds for haptic perception of volume, surface area, and weight

The present study investigated the human ability to discriminate the size of 3-D objects by touch. Experiment 1 measured the just noticeable differences (JNDs) for three tasks: (1) discrimination of volume without availability of weight information, (2) discrimination of volume with weight information available, and (3) discrimination of surface area. Stimuli consisted of spheres, cubes, and tetrahedrons. For all shapes, two reference sizes were used (3.5 and 12 cm(3)). No significant effect of task on the discriminability of objects was found, but the effects of shape and size were significant, as well as the interaction between these two factors. Post hoc analysis revealed that for the small reference, the Weber fractions for the tetrahedron were significantly larger than the fractions for the cube and the sphere. In Experiment 2, the JNDs for haptic perception of weight were measured for the same objects as those used in Experiment 1. The shape of objects had no significant effect on the Weber fractions for weight, but the Weber fractions for the small stimuli were larger than the fractions for the large stimuli. Surprisingly, a comparison between the two experiments showed that the Weber fractions for weight were significantly larger than the fractions for volume with availability of weight information. Taken together, the results reveal that volume and weight information are not effectively combined in discrimination tasks. This study provides detailed insight into the accuracy of the haptic system in discriminating objects' size. This substantial set of data satisfies the need for more fundamental knowledge on haptic size perception, necessary for a greater understanding of the perception of related properties, as well as of more general perceptual processes.