An improved shocking surface for pigeons and rats

A resistive shocking surface and an appropriate power supply are described. The efficacy of the system is illustrated with some data on the activity of pigeons and rats as a function of the voltage applied.     

An improved photoelectric system for two-dimensional eye movement recording

Established photoelectric methods for measuring two-dimensional eye movements exist, but they suffer from a number of practical limitations, including inflexibility of the design, thermal drift, and difficulties in setting up and calibrating the system. In this paper, an improved design of transducer is described, together with a computerized method of calibration. Finally, some performance measurements are presented, showing the system to have an accuracy of a few minutes of arc.     

Classical aversive conditioning of heart rate in curarized rats at different blood gas levels

In an effort to examine whether normal blood gas tensions were essential for conditioning, paralyzed rats received a classical aversive heart rate (HR) conditioning session while respirated at different peak expired CO₃ values. After the session, arterial blood was drawn for analysis. That peak expired CO₂ was effective in manipulating Pco₂ was indicated by a significant correlation (r = 0.594, df = 17, P < 0.05). In addition, only rats with blood gas values similar to those of anesthetized controls displayed a discriminated HR CR. These animals also had lower baseline HRs and greater HR variability. Further, 7 of the 9 rats with normal blood gas values were respirated at peak expired CO₂ values from 5.0–5.1 per cent, and no animal ventilated within this range displayed abnormal values. These findings suggest that previous difficulties in obtaining classical and operant conditioning in paralyzed animals may, in part, be attributable to inadequate ventilation.     

An improved method for tetrachoricr

From the ratio of the cross-products of a fourfold table, with the application of two tabled corrections, tetrachoricr's can be estimated with a mean discrepancy of less than .005 even when splits vary greatly from the medians. The necessary calculations can be handled by slide rule and the correction tables used without interpolation.     

An improved video multiplexer for behavioral research

Wellens and Revert (1979) described a solid-state circuit that allowed two sources of video information to be multiplexed and recorded using one videotape machine. On playback, the demultiplexed video signal allowed the original video channels to be viewed independently on separate television monitors. Recent changes in videocassette recorder technology have improved the playback quality of recorded images but disrupt the demultiplexing process when freeze frame or search options are selected. Improved multiplexing techniques that overcome these limitations are described.     

An improved technique for creating hemifacial chimeras

In numerous studies, facial composites of the right and left hemifaces have been used to explore lateral differences in facial expressions. In the majority of these studies, a single technique has been used to create the stimuli: “Wolff’s split half technique,” which was devised at the beginning of the century. Chimeras thus made are weakened by several confounding factors (e.g., hair form, background, shadows), which are unrelated to the original stimuli and consequently may interfere with the examination of subtle facial expressions. This paper offers a modified method using computer graphics that seems to solve such drawbacks.     

An improved algorithm for predicting free recalls

Laming [Laming, D. (2006). Predicting free recalls. Journal of Experimental Psychology: Learning, Memory, and Cognition, 32, 1146-1163] has shown that, in a free-recall experiment in which the participants rehearsed out loud, entire sequences of recalls could be predicted, to a useful degree of precision, from the prior sequences of stimuli and rehearsals. This article describes an improved predictive algorithm, which is then used to re-analyse two further sets of free-recall data. Prediction is compared, generically, with conventional modelling, represented here by three recent models of free recall that are concerned with recalls only, not with rehearsals. Some implications are drawn, from the use of rehearsal data by the predictive algorithm, for some of the constituent assumptions embodied in those three models.     

An improved circuit for control of LED luminance

The light-emitting diode (LED) is becoming increasingly popular as a luminance source in behavioral research. We describe a simple, inexpensive LED driver circuit that produces luminances almost linearly proportional to an input voltage. Negative feedback provides a stable output. Unlike previous designs, the LED is ground referenced.     

An operant arena for rats

A multiunit operant arena for the study of dispersion patterns in rats is described. Lawful relationships between the spatiotemporal organization of the group and reinforcement schedules have been found. The scientific and humanistic advantages of the system are discussed.