Information flow in the brain: Computer requirements (A tutorial)

This paper covers mathematical, statistical, and experimental design considerations needed to design a computer system for EEG data acquisition, spectrum, and cross-spectrum analyses. A tutorial approach is used in which no formal proofs are offered. Conclusions are stated simply and in summary fashion, without justifying arguments. References to formal works are given. Conclusions about system design are discussed. Frequently encountered design issues are mentioned with various alternatives.     

Recognition models evaluated: A commentary on Keren and Baggen

In a recent paper (1981), Keren and Baggen proposed two new models for alphanumeric confusion data, based on Tversky’s (1977) feature model of similarity, and compared them with Luce’s (1963) biased choice model. On the basis of their data, they concluded that, although the choice model fit slightly better, their models were to be preferred on grounds of parsimony and interpretability. It is shown here that both of these models are special cases of the Luce model, so that the general Luce model will necessarily fit better. This leads to considerable reinterpretation of Keren and Baggen’s conclusions. Finally, better methods of estimating parameters and evaluating goodness-of-fit are suggested, taking advantage of this relation between the models.     

Power functions of loudness magnitude estimations and auditory brainstem evoked responses

The correspondence between subjective and neural response to change in acoustic intensity was considered by deriving power functions from subjective loudness estimations and from the amplitude and latency of auditory brainstem evoked response components (BER). Thirty-six subjects provided loudness magnitude estimations of 2-sec trains of positive polarity click stimuli, 20/sec, at intensity levels ranging from 55 to 90 dB in 5-dB steps. The loudness power function yielded an exponent of .48. With longer trains of the same click stimuli, the exponents of BER latency measures ranged from -.14 for wave I to -.03 for later waves. The exponents of BER amplitude-intensity functions ranged from .40 to .19. Although these exponents tended to be larger than exponents previously reported, they were all lower than the exponent derived from the subjective loudness estimates, and a clear correspondence between the exponents of the loudness and BER component intensity functions was not found.     

A further study of melodic channeling

Subjects listened to repetitive presentations of C major scale patterns and simple two-part contrapuntal specimens, both dichotically and in a stereophonic free sound field. All scalar and melodic patterns were presented so that successive tones alternated from ear to ear: when a component of one scale or melody was routed through one speaker or headphone, the concurrent member of the other scale or melodic pattern was routed through the other speaker or headphone, and vice versa. The stimulus parameters of spectral contour and envelope characteristics, duration, melodic pattern, and loudness were varied, and a testing procedure was designed to minimize any bias in responses which might be produced by learning, immediate memory, or vocal Limitations of subjects. Virtually all responses (95.2% to scalar stimuli, 99.1% to melodic stimuli) indicated that the subjects channeled stimuli by pitch range, and not by ear of input. When spectral contours routed through the separate headphones or speakers were noticeably dissimilar, no subject perceived that this timbral inequality switched from ear to ear: all subjects heard an overall change in tone quality which pervaded both scalar or melodic sequences, and which apparently emanated from both headphones or speakers.     

The form of analog size information in memory

The information used to choose the larger of two objects from memory was investigated in two experiments that compared the effects of a number of variables on the performance of subjects who either were instructed to use imagery in the comparison task or were not so instructed. Subjects instructed to use imagery could perform the task more quickly if they prepared themselves with an image of one of the objects at its normal size, rather than with an image that was abnormally big or small, or no image at all. Such subjects were also subject to substantial selective interference when asked to simultaneously maintain irrelevant images of digits. In contrast, when subjects were not specifically instructed to use imagery to reach their decisions, an initial image at normal size did not produce significantly faster decisions than no image, or a large or small image congruent with the correct decision. The selective interference created by simultaneously imaging digits was reduced for subjects not told to base their size comparisons on imagery. The difficulty of the size discrimination did not interact significantly with any other variable. The results suggest that subjects, unless specifically instructed to use imagery, can compare the size of objects in memory using information more abstract than visual imagery.     

Visual-feature and response components in a picture-word interference task with beginning and skilled readers

A series of four experiments is reported in which reaction times for naming line drawings were analyzed as a function of the similarity of the print superimposed on the drawings to the printed label for the drawing. This effect was studied as a function of grade level (ages 6, 8, and 11 years) and, hence, reading experience. The studies were designed to determine more precisely the characteristics of the stage of visual feature analysis of word identification and to examine response competition factors in this interference task. Results indicated that a combination of end letters and word shape was important for word identification and that response articulation was a significant distinct interference component in this task.     

SKED-controlled experimentation in an undergraduate instructional laboratory

A SKED-based facility for undergraduate instructional research has been operating for over a year. The two-computer approach, with one machine for programming and the other for running experiments, is used. Criteria for computerized undergraduate research laboratories, benefits of SKED, and the two-computer approach are discussed.     

Book Review

International Journal for Philosophy of Religion -