Weber’s Law and the Scalar Property of Timing: A Test of Canine Timing

Domestic dogs completed a temporal bisection procedure that required a response to one lever following a light stimulus of short duration and to another lever following a light stimulus of a longer duration. The short and long durations across the four conditions were (0.5–2.0 s, 1.0–4.0 s, 2.0–8.0 s, and 4.0–16.0 s). Durations that were intermediate, the training durations, and the training durations, were presented during generalization tests. The dogs bisected the intervals near the geometric mean of the short and long-stimulus pair. Weber fractions were not constant when plotted as a function of time: A U-shaped function described them. These results replicate the findings of previous research reporting points of subjective equality falling close to the geometric mean and also confirm recent reports of systematic departures from Weber’s law.

Subhypnotic Doses of Isoflurane Impair Auditory Discrimination in Rats

Background Isoflurane at subhypnotic doses is known to affect cellular and network activity in the auditory pathway, but the behavioral effects of these concentrations of isoflurane on auditory processing have not been tested previously. The authors tested the hypothesis that subhypnotic doses of isoflurane would impair auditory discrimination in rats. Methods Rats were tested on their ability to discriminate up versus down frequency-modulated sweeps using three different pairs of sweeps ("Long," "Med," "Short"), whose frequency range and duration were varied systematically to make the discrimination more difficult. Rats were tested daily in the absence and presence of isoflurane at 0.2% or 0.4%. The effects of isoflurane (0%, 0.2%, and 0.4%) on performance (= % correct) and efficiency (= time/trial) were assessed using regression analysis. Results The effect of isoflurane was stimulus-dependent: performance for the Long stimulus pair was unaffected by isoflurane, performance on the Med stimulus pair was impaired only by 0.4% isoflurane, and performance on the Short stimulus pair was impaired by both 0.2% and 0.4% isoflurane. In contrast, isoflurane decreased efficiency equally for all stimulus pairs at 0.4% and had no effect at 0.2%. Conclusions The stimulus dependence of the effect of isoflurane on performance suggests that it is unlikely this effect was secondary to effects on memory, motivation, or motor function. These data indicate that doses of isoflurane known to produce modest effects on neural responses alter cortical sensory processing.

Apparent Relative Size in the Judgement of Apparent Distance

In experiment 1 judgements of the apparent distance of comparison figures (squares or triangles) were obtained under reduction conditions. These comparison figures were either shaped the same as or different from equidistant standard figures, and were half, equal to, or double the area of the standard figures. Apparent distance was found to be a linear function of the relative area of the comparison figure both in same-shape and different-shape stimulus pair conditions. In addition, apparent distance was found to be a function of perceived area, because in different-shape conditions triangles were generally seen to be closer than squares even when the real area of the standard and comparison was equal. The results of experiment 2 and 3 provide some evidence that the effect of different shapes of standard and comparison on apparent distance is due to the observers' perception of the height rather than the area of figures. The series of experiments shows that the traditional transactionalists' explanation of relative size as a cue for distance is inadequate.

Physical and Name Codes in Auditory Memory: The Pursuit of an Analogy

Subjects decided whether successive auditory stimuli were the same word or not in an RT task. Same decisions tended to be faster when the second stimuli was physically identical. Intonation change and, even more, speaker change slowed some decisions. These voice effects were contributed by the slower responders and they disappeared over the six sessions of testing. Increasing the delay between the stimulus pair slowed RT but delay did not interact with voicing. These results suggest that the auditory analogy with visual physical and name codes is misleading. Non-linguistic information from the speech signal survives in various forms but this fact does not entail the existence of a literal physical code in audition.

Iconic Memory of Dot Patterns: Preliminary Report

Pairs of complementary dot-pattern stimuli whereby each stimulus pair forms a bigram were used in an iconic memory paradigm. The variables of stimulus dutation, interstimulus interval, dot density, and letter field were all shown to affect recognition performance of 15 naive college students.