THIS PAPER is concerned with the nature of the tutorial process; the means whereby an adult or "expert" helps somebody who is less adult or less expert. Though its aim is general, it is expressed in terms of a particular task: a tutor seeks to teach children aged 3, 4 and 5 yr to build a particular three-dimensional structure that requires a degree of skill that is initially beyond them. It is the usual type of tutoring situation in which one member "knows the answer" and the other does not, rather like a "practical" in which only the instructor "knows how". The changing interaction of tutor and children provide our data.A great deal of early problem solving by the developing child is of this order. Although from the earliest months of life he is a "natural" problem solver in his own right (e.g. Bruner, 1973) it is often the ease that his efforts are assisted and fostered by others who are more skilful than he is (Kaye, 1970). Whether he is learning the procedures that constitute the skills of attending, communicating, manipulating objects, locomoting, or, indeed, a more effective problem solving procedure itself, there are usually others in attendance who help him on his way. Tutorial interactions are, in short, a crucial feature of infancy and childhood. Our species, moreover, appears to be the only one in which any "intentional" tutoring goes on (Bruner, 1972;Hinde, 1971). For although it is true that many of the higher primate species learn by observation of their elders (Hamburg, 1968; van Lawick-Goodall, 1968), there is no evidence that those elders do anything to instruct their charges in the performance of the skill in question. What distinguishes man as a species is not only his capacity for learning, but for teaching as well. It is the main aim of this paper to examine some of the major implications of this interactive, instructional relationship between the developing child and his elders for the study of skill acquisition and problem solving.The acquisition of skill in the human child can be fruitfully conceived as a hierarchical program in which component skills are combined into "higher skills" by appropriate orchestration to meet new, more complex task requirements (Bruner, 1973). The process is analogous to problem solving in which mastery of "lower order" or constituent problems in a sine qua non for success with a larger jjroblcm, each level influencing the other-as with reading where the deciphering of words makes possible the deciphering of sentences, and sentences then aid in the deciphering of particular words (F. Smith, 1971). Given persistent intention in the young learner, given a "lexicon" of constituent skills, the crucial task is often one of com-

Porcine small intestinal submucosa (SIS) has been recommended as a cell-free, biocompatible biomaterial for the repair of rotator cuff tendon tear. However, we have observed noninfectious edema and severe pain in patients who have undergone SIS implantation for tendon repair. The aim of this study was to conduct an independent assessment of the safety and efficacy of Restore SIS membrane. The Restore orthobiologic implant was examined by histology and the nested PCR technique using porcine immunoreceptor DAP12 gene to examine if SIS membrane contained porcine cells or DNA, respectively. The material was also implanted into mice and rabbits for the evaluation of biological reaction and inflammatory response. Restore SIS was found to contain multiple layers of porcine cells. Chloroacetate esterase staining showed that some of these cells were mast cells. Nested PCR of the DAP12 gene demonstrated that Restore SIS contained porcine DNA material. Subcutaneous implantation of Restore SIS membrane in mice, and in rabbits for rotator cuff tendon repair, showed that the membrane caused an inflammatory reaction characterized by massive lymphocyte infiltration. In conclusion, Restore SIS is not an acellular collagenous matrix, and contains porcine DNA. Our results contradict the current view that Restore SIS is a cell-free biomaterial, and that no inflammatory response is elicited by its implantation. We suggest that further studies should be conducted to evaluate the clinical safety and efficacy of SIS implant biomaterials.

This study examines the interactions between 12 mothers and their children in a problem‐solving situation. Each child tries to assemble a construction toy, and his mother attempts to help him in such a way that he will eventually be able to do it alone. The paper introduces a system for describing the course of these interactions and it tests and confirms hypotheses relating to the underlying determinants of effective instruction. Those mothers who systematically changed their instructions on the basis of the child's response to earlier interventions (and the system of analysis enables such changes to be identified and related) were most likely to see their child perform effectively after instruction. They were also the most likely to determine and concentrate upon the child's ‘region of sensitivity to instruction’ — a hypothetical measure of the child's current task ability and his ‘readiness’ for different types of instruction. The study shows that effective instructing is a dynamic, interactive process somewhat akin to problem‐solving. It elaborates the view that the process of intellectual development must be viewed as a social, interactive one.

The outcomes of this randomized trial demonstrate a safe and effective accelerated rehabilitation protocol as well as a regimen that provides comparable, if not superior, clinical outcomes to patients throughout the postoperative timeline.