An interval scale of saturation for the pigeon

Pigeons were required to discriminate between “identical” vs. “different” pairs of lights in a yes/no signal-detection task with a symmetrical payoff matrix. If the two lights projected on the two halves of the bipartite field constituting the center response key in a three-key chamber were identical in wavelength composition, then a single peck on the left key was reinforced with food. If the two lights differed in wavelength composition, then right-key pecks were reinforced. Each pigeon experienced all possible pairs (55) of 11 lights having the same dominant hue (630 nm) but differing in colorimetric purity. The percentage of correct responses was taken as a measure of the dissimilarity between the two lights constituting a pair. The rank-order information available in these dissimilarity measures was used to determine an interval scale of saturation in the pigeon. Saturation was found to be linearly related to colorimetric purity.     

The development of letter processing efficiency

The development of efficiency in letter processing skills was studied using a letter search task. In two experiments, subjects searched for a target letter displayed with items varying in their visual featural or conceptual categorical similarity to the target. Accuracy and reaction time of search were evaluated for evidence of the visual search “category effect.” In order to determine if subjects could efficiently use knowledge of stimulus differences to facilitate search, conditions tested search time as a function of the amount of information to be processed both within the visual display and in short-term memory. In the two experiments, subjects of ages 6 years through adulthood showed the category effect; however, efficiency of letter processing was found to be related to the amount of information that had to be processed in memory. While there were drastic changes in search speed with increasing grade level, patterns of processing were consistent, leading to the conclusion that the knowledge required to process the letter information accurately is acquired very early. Results were discussed in terms of the distinctions among accuracy, automaticity, and efficiency of skill development and the relationship of these to general reading and intellectual development.     

The measurement of loudness using direct comparisons of sensory intervals

Subjects were required in each trial to directly compare two pairs of tones and indicate which pair of tones had the greater loudness difference. Ten 1200 Hz tones differing only in intensity were employed. Subjects made binary comparisons among the 45 tone pairs which can be formed from the set of ten tones. The subjects' binary comparisons of the tone pairs were found to satisfy the transitivity and monotonicity requirements of a positive difference structure. These comparisons of loudness intervals were used to construct a rank order of loudness difference. A loudness scale was constructed from a nonmetric analysis of the rank order of loudness difference for the 45 tone pairs and indicated that loudness was a power function of sound pressure with an exponent of 0.26.     

Requirements for minicomputer operating systems for human experimentation and an implementation on a 4K PDP-8 computer

A programming system is described which considerably simplifies preparation and running of experiments on PDP-8 computers.     

Tables of d’ for detection and localization

A detection and localization (DAL) procedure (Hershman and Lichtenstein, 1967) is one in which at most one of k noisy observation intervals contains a signal. The observer must detect the signal (if present) and locate it in the proper interval. Tables are given for the extraction of d’ values from the percentage of correct responses made in such experiments.     

A two-state analysis of fixed-interval responding in the pigeon

The behavior of pigeons on six geometrically spaced fixed-interval schedules ranging from 16 to 512 sec is described as a two-state process. In the first state, which begins immediately after reinforcement, response rate is low and constant. At some variable time after reinforcement there is an abrupt transition to a high and approximately constant rate. The point of rapid transition occurs, on the average, at about two-thirds of the way through the interval. Response rate in the second state is an increasing, negatively accelerated function of rate of reinforcement in the second state.     

A review of scientific visualization software for the Macintosh computer

Many programs are available for the Macintosh that provide advanced visualization tools. Some of the tools are individual applications, and some are part of mathematical packages. This paper reviews the capabilities, functionality, and ease of use of visualization tools within six software packages: Mathematica, Spyglass Transform/View, Spyglass Dicer, JMP, MacSpin, and SYSTAT.     

The effectiveness of dynamic graphics in revealing structure in multivariate data

Previous work by the authors showed no significant benefit for dynamic graphical presentation as opposed to static scatterplots in determining the number of data clusters present in multidimensional data sets. In the present study, subjects interactively looked for different types of structure, such as linear trends, clusters, or increases in variance of one variable, rather than discriminating number of clusters, to more closely mimic actual exploratory data-analysis features of interest. Searching for structure failed to prove significant benefits for dynamic data presentation.     

Sequences of spaced responses: Behavioral units and the role of contiguity

Sequences of temporally spaced responses were reinforced to investigate the effects of delay of reinforcement on the formation of functional behavioral units. In Experiment 1, rats' two- and three-response demarcated sequences of left and right lever presses were reinforced such that different response distributions would occur depending on whether the sequences themselves or individual responses were functional units. The matching law could thus be obeyed either by individual responses or by sequences, but not by both; intermediate results were possible. Both regular (nonretractable) and retractable levers were used; the retractable levers precluded the occurrence of insufficiently spaced responses. At a minimum interresponse time of 5 s for regular levers and 7 s for retractable ones, matching results were intermediate, with greater evidence of sequence conditionability in the two-response sequences than in the three-response sequences. In Experiment 2, the required minimum interresponse spacing for two-response retractable-lever sequences was varied in an attempt to locate the sequence matching threshold. This attempt was unsuccessful, but the sequences (instead of individual responses) more closely obeyed the matching law. In the shortest spaced condition, conditional probability data on Lag 1 sequence emission order showed marked, highly similar patterning for all rats, indicating sequential control of the sequences. Post hoc definition of the behavioral unit in these studies is ambiguous. Although reinforcement contiguity was important, aspects of the results could support both molar- and molecular-level interpretations.