Effects of prior experimenter-subject relationships on reinforced reaction time of schizophrenics and normals.

The hypothesis was tested that deficits in schizophrenics' responses to positive social reinforcers would be reduced if reinforcers were delivered by an E who had first related to the Ss in a warm and accepting manner. Reaction times of 39 chronic schizophrenics and 39 normal adults were tested without and with reinforcement after exposure to 1 of 3 conditions of contact with E: (a) no contact, (b) contact with an unresponsive and aloof E, and (c) contact with a warm and accepting E. Schizophrenics had slowest reaction times after c. Normals had slowest reaction times after c until reinforced; on reinforced trials there were no differences between conditions for normal Ss. The results indicate that chronic schizophrenics can be motivated to gain approval but that such motivation in schizophrenics is more dependent upon immediate social circumstances than it is in normal adults. (29 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Unified Representation of Differential Pulse-Code Modulation (DPCM) and Transform Coding Systems

We consider a transform coding system that uses a lower-triangular transformation to uncorrelate the data. Based on this transformation we propose a generalized differential pulse code modulation (DPCM) system and show that at high bit rates it performs almost as well as coding by the method of principal components (Karhunen-Loeve transformation). This study connects the transform coding system to the DPCM encoder by showing that the proposed system simplifies to a standard DPCM encoder for Markov data.