Effects on stereotypy and other challenging behavior of matching rates of instruction to free-operant rates of responding.

Research has shown that when individuals are in situations that do not occasion one form of motoric responding, they will engage in another so that the overall level of motoric responding is homeostatic. The purpose of this study was to test whether students would substitute task-related behaviors for stereotypic or other challenging behaviors when the opportunity for active responding did or did not match the level of motoric responding in a free-operant baseline. Four students with mental retardation participated. Results showed that they did substitute behaviors, with stereotypic and other challenging behaviors occurring 1.5-14 times as much in the Non-matched condition for the four students. Further analysis showed considerably more of these behaviors in passive than in active tasks (by a factor up to 21 times as much). Results were discussed in terms of homeostasis, functional assessment, and opportunities to improve educational behaviors.

Discrimination training: a comparison of two procedures for presenting multiple examples within a fading and non-fading paradigm.

When teaching discriminations, many researchers and practitioners recommend presenting multiple examples of both the correct and incorrect stimuli. To test this suggestion, we compared two procedures for presenting multiple examples. In one, multiple examples across trials (ME, Across), one correct (S+) and one incorrect (S-) stimulus were presented each trial; examples then changed across trials. In another procedure, multiple examples within trials (ME, Within), three stimuli (either 2 S+'s and 1 S-, or 1 S+ and 2 S-'s) were presented each trial; examples again changed across trials. Two experiments were conducted to test these procedures. The first procedure used a non-fading program to teach discrimination; the second used a fading procedure. In the first experiment, we taught 10 persons to identify words under these two procedures. The former procedure was superior in acquisition; the latter procedure, however, was better under generalization for most participants. In the second experiment, we presented the two procedures within a fading paradigm. The results replicated those in Experiment 1: ME, Across was better for acquisition, but ME, Within was better for generalization. Results were discussed and follow-up studies suggested.

Ancient DNA analysis of mid-holocene individuals from the Northwest Coast of North America reveals different evolutionary paths for mitogenomes.

To gain a better understanding of North American population history, complete mitochondrial genomes (mitogenomes) were generated from four ancient and three living individuals of the northern Northwest Coast of North America, specifically the north coast of British Columbia, Canada, current home to the indigenous Tsimshian, Haida, and Nisga'a. The mitogenomes of all individuals were previously unknown and assigned to new sub-haplogroup designations D4h3a7, A2ag and A2ah. The analysis of mitogenomes allows for more detailed analyses of presumed ancestor-descendant relationships than sequencing only the HVSI region of the mitochondrial genome, a more traditional approach in local population studies. The results of this study provide contrasting examples of the evolution of Native American mitogenomes. Those belonging to sub-haplogroups A2ag and A2ah exhibit temporal continuity in this region for 5000 years up until the present day. Of possible associative significance is that archaeologically identified house structures in this region maintain similar characteristics for this same period of time, demonstrating cultural continuity in residence patterns. The individual dated to 6000 years before present (BP) exhibited a mitogenome belonging to sub-haplogroup D4h3a. This sub-haplogroup was earlier identified in the same general area at 10300 years BP on Prince of Wales Island, Alaska, and may have gone extinct, as it has not been observed in any living individuals of the Northwest Coast. The presented case studies demonstrate the different evolutionary paths of mitogenomes over time on the Northwest Coast.