On the estimation of parameters in latent structure analysis

In this note, we describe the iterative procedure introduced earlier by Goodman to calculate the maximum likelihood estimates of the parameters in latent structure analysis, and we provide here a simple and direct proof of the fact that the parameter estimates obtained with the iterative procedure cannot lie outside the allowed interval. Formann recently stated that Goodman's algorithm can yield parameter estimates that lie outside the allowed interval, and we prove in the present note that Formann's contention is incorrect.This research was supported in part by Research Contract No. NSF SOC 76-80389 from the Division of the Social Sciences of the National Science Foundation. The author is indebted to C. C. Clogg for helpful comments and for the numerical results reported here (see, e.g., Table 1).     

Liquid-specific stimulus properties can be used for haptic perception of the amount of liquid in a vessel put in motion

We investigated whether people can use haptic liquid-specific information made available by shaking the vessel containing the liquid. In experiment 1 we studied to what extent people can discriminate between liquid and solid substances and determine the amount of substance in the shaken vessel, as well as the effects of exploratory procedures on these abilities. Exploratory procedures including horizontal shaking of the vessel produced accurate identification of the content and more precise judgments for a liquid than for a solid, but vertical lifting produced an overestimation of the amount of liquid. In experiment 2 we demonstrated that people can discriminate between the amount of liquid and the amount of solid in the same vessel. Three theories of what liquid-specific stimulus properties are picked up by shaking the vessel are preliminarily examined.     

Three-month-olds' visual preference for faces and its underlying visual processing mechanisms

This study was aimed at investigating the face preference phenomenon and its underlying mechanisms at 3 months of age. Using an eye-tracker apparatus, Experiment 1 demonstrated that 3-month-olds prefer natural face images to unnatural ones, replicating and extending previous evidence obtained with schematic facelike stimuli. Experiments 2 and 3 showed that the general mechanisms that induce face preference in newborns could not explain the same phenomenon at 3 months of age, when infants are attracted by perceptual cues more specific to faces. This suggests that signs of a process of cognitive specialization are already present in 3-month-olds' visual behavior toward faces.     

Colour, polarity, disparity, and texture contributions to motion segregation

We measured how different cues are combined in motion-segregation processes by using motion stimuli where randomly distributed target dots were organised in global revolving motion while the remaining noise dots performed random motion. Target dots were cued with a different colour, polarity, disparity depth, or texture orientation than the noise dots, or they were the same as the noise dots. The stimuli were presented with a prolonged static cue preview which provided position cues to target dots or, briefly with static pre-target and post-target noise frames, which provided false position cues (no preview). All cues efficiently facilitated global motion segregation in cued-preview conditions. Colour completely failed to facilitate global motion segregation in no-preview conditions. Polarity and disparity facilitated segregation in no-preview conditions, although sensitivities were lower than in the preview conditions. Remarkably, texture orientation largely facilitated motion segregation by the same amount in both cued-preview and no-preview conditions. So, colour provides only position cues to the motion-segregation task whereas texture orientation, disparity, and to a lesser extent polarity are integrated with the segregation process.     

A program for fitting two-phase segmented-curve models with an unknown change point,with an application to the analysis of strategy shifts in a cognitive task

A program is described for fitting a regression model in which the relationship between the dependent and the independent variables is described by two regression equations, one for each of two mutually exclusive ranges of the independent variable. The point at which the change from one equation to the other occurs is often unknown, and thus must be estimated. In cognitive psychology, such models are relevant for studying the phenomenon of strategy shifts. The program uses a (weighted) least squares algorithm to estimate the regression parameters and the change point. The algorithm always finds the global minimum of the error sum of squares. The model is applied to data from a mental-rotation experiment. The program’s estimates of the point at which the strategy shift occurs are compared with estimates obtained from a nonlinear least squares minimization procedure in SPSSX.     

The experimental determination of unique green in the spectrum

The notion is gaining currency that observers who are distributed normally with respect to commonly measured indices of color vision, may be bimodally distributed with respect to the spectral locus of unique green. Experimental conditions which can produce such deviations from a normal distribution are explored, and it is concluded that the “bimodality” results reported in the literature may reflect differential chromatic adaptation effects. Experimental conditions which guarantee a neutral state of adaptation yield spectral unique green loci that show no evidence of bimodality.     

The variance of the number of mutual choices in sociometry

The variance of the number of mutual dyads in a sociometric situation where each member of a group chooses independently and at random is derived for unrestricted numbers of choices per group member, as well as for a fixed number of choices. The distribution of the number of mutuals is considered.We are indebted to Robert Bush and Hartley Rodgers of Harvard University for helpful criticisms.