Diminished weight loss and behavioral compliance during repeated diets in obese patients with type II diabetes.

Compared weight losses during first and second bouts of a very low calorie diet (VLCD) and examined whether decreased compliance might in part explain the decrease in weight loss during the second bout. Forty-five Type II diabetic patients participated in a year-long behavioral weight-reduction program that incorporated a VLCD (400 to 500 kcal/day) during Weeks 1 to 12 and 28 to 40. Weight losses decreased dramatically from the first to the second VLCD (15.54 vs. 1.42 kg, p less than .0001). There was also markedly diminished adherence as assessed by weeks ketonuric, attendance, and completeness of self-monitoring records. The percentage of weeks subjects were in ketosis dropped from 61% during VLCD 1 to 13% during VLCD 2 (p less than .0001). Similarly, subjects attended significantly fewer treatment meetings during VLCD 2 and self-monitored less during VLCD 2 than during VLCD 1. Weeks ketonuric and initial weight accounted for 63% of the variance in weight loss during VLCD 1 (p less than .0001); weeks ketonuric and attendance predicted weight loss during VLCD 2 (p less than .0001), accounting for 54% of the variance. These results suggest the importance of behavioral factors in explaining poorer performance on a repeated diet.     

Symmetry, gestalt and information theory: A critique

A criticism of a recent analysis of matrix pattern perception is advanced. It is pointed out that a fair test of the equivalence for performance of different forms of redundancy must be framed in terms of the measure of transmitted information.     

Multidimensional encoding of visual form

The encoding of stimulus dimensions of visual form in the human S was investigated under conditions of threshold exposure durations. Three stimulus dhnensions defined on a spatial grating were investigated: spatial line frequency, grating orientation, and orientation of a transverse break in the lines of grating. Results support the conclusion that, within the general category of visual form, different primary stimulus dimensions such as spatial frequency and orientation may be encoded simultaneously, whereas, when the two stimulus components for report are defined on the same dimension (orientation), overall performance is consistent with the predictions of a single channel model.     

Statistical dependence in response timing: A critique of reece 1976

The existence of an error is pointed out in the theoretical development of Reece's (1976) article ‘A model of temporal tracking’. Because his data presentation consists entirely of estimates based on an incorrect equation, his article fails to make an empirical contribution and his conclusions should be discounted.     

Preference for simple interval schedules of reinforcement in concurrent chains: Effects of segmentation ratio

A concurrent-chains procedure was used to examine pigeons' preferences between segmented and unsegmented terminal-link schedules of reinforcement. During the initial link, a pair of independent, concurrent variable-interval 60-s schedules was in effect. In the terminal link, reinforcement was provided by a chain fixed-interval fixed-interval schedule on one key and by a simple fixed-interval schedule with an equal interreinforcement interval in the other. The relative duration between the first and second components (segmentation ratio) in the terminal-link chained schedule was systematically varied while the terminal-link duration was kept constant at either 15 s or 30 s in two sets of conditions. With few exceptions, the simple schedule was preferred to the chained schedule. Furthermore, this preference was inversely related to the size of the segmentation ratio in the segmented schedule. When the segmentation ratio was smaller than 1:1, preference was more extreme for a 30-s condition than for a 15-s condition. However, preference decreased more rapidly in conditions with the longer terminal-link duration when the ratio increased. Taken together, these results were consistent with previous findings concerning the effect of the terminal-link duration on choice between segmented and unsegmented schedules. In addition, the data suggested that segmentation ratio in a segmented schedule constitutes another potent factor influencing preference for the unsegmented schedule.     

Effects on weight reduction of strong monetary contracts for calorie restriction or weight loss

Thirty-one severely obese adults participated in behavioral weight control groups. In three groups utilizing powerful monetary contracts, subjects deposited substantial sums of money which were returned contingent on either attendance, calorie restriction, or weight loss. Subjects in a fourth no-contract control condition made no monetary deposits. Weight and calorie contract groups lost an average of nearly 20 lb in 10 weeks. They did not differ from each other, but both produced significantly more weight loss than the attendance contract group. High dropout rates in the no-contract condition precluded statistical evaluation of this group. Results are discussed in terms of the potential clinical value of contracting procedures.