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.     

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.     

Accuracy of parents' reports of height and weight

The accuracy of parents' reports of their own height and weight and the height and weight of their obese children, who were about to enter a weight control program, was assessed. Measured height and weights of 146 mothers, 55 fathers, and 150 children who attended a screening session were compared to the heights and weights they had previously reported on a demographic questionnaire. Eighty-four percent of the reported weights were accurate within ±5 lbs.; 71% of the reported heights were accurate within ±1 in. Parents' reports of weight tended to underestimate actual weights, with the magnitude of underestimation greater for mothers than for fathers, while reported heights overestimated actual height, with the magnitude of overestimation greatest for fathers. Errors in the parents' reports of children's weight were related to the child's actual weight and body mass index (BMI), with substantial underestimation of actual weight in the heaviest decile of children in the sample.Preparation of this paper was supported in part by Grant HDMH12520-01 from the National Institute of Child Health and Human Development and Mental Health. Reprints can be obtained from Rena R. Wing, Western Psychiatric Institute and Clinic, 3811 O'Hara Street, Pittsburgh, PA 15261.     

Inertia and memory in ambiguous visual perception

Perceptual multistability during ambiguous visual perception is an important clue to neural dynamics. We examined perceptual switching during ambiguous depth perception using a Necker cube stimulus, and also during binocular rivalry. Analysis of perceptual switching time series using variance–sample size analysis, spectral analysis and time series shuffling shows that switching times behave as a 1/f noise and possess very long range correlations. The long memory feature contrasts sharply with the traditional satiation models of multistability, where the memory is not incorporated, as well as with recently published models of multistability and neural processing, where memory is excluded. On the other hand, the long memory feature favors the concept of “dynamic core” or coalition of neurons, where neurons form transient coalitions. Perceptual switching then corresponds to replacement of one coalition of neurons by another. The inertia and memory measures the stability of a coalition: a strong and stable coalition has to be won over by another similarly strong and stable coalition, resulting in long switching times. The complicated transient dynamics of competing coalitions of neurons may be addressable using a combination of functional imaging, measurement of frequency-tagged magnetoencephalography and frequency-tagged encephalography, simultaneous recordings of groups of neurons in many areas of the brain, and concepts from statistical mechanics and nonlinear dynamics theory.