A new method for calibrating perceptual salience across dimensions in infants: the case of color vs. luminance

We report a new method for calibrating differences in perceptual salience across feature dimensions, in infants. The problem of inter-dimensional salience arises in many areas of infant studies, but a general method for addressing the problem has not previously been described. Our method is based on a preferential looking paradigm, adapted to determine the relative salience of two stimuli. We report here on the case of stimuli differing in color and luminance, though the method has wider potential. We were able to determine on a psychophysical curve the point at which a color contrast was equally salient to infants as a given luminance contrast. We then used these calibrated, 'iso-salient' stimuli in an object memory study. Results showed that 6.5-month-old infants noticed a color, but not a luminance, change while tracking an occluded object. Our method should have numerous applications in the study of bottom-up effects on infant attention and visual working memory.     

An automated eye movement recording system for use with human infants

An infrared corneal reflection eye movement system modified for work with human infants is described. The system generates on-line digital information on eye position at a sampling rate that allows examination of the temporal and spatial characteristics of fixations and eye move-ments. An algorithm for defining fixation and eye movement episodes is described.     

A method for calibrating the spatial coordinates of a visual display to high accuracy

High-resolution CRT displays are subject togeometric distortion: lines that are straight in the internal coordinates of the graphics software and hardware are curved when projected onto a plane in the observer’s line of sight. As the available resolution of CRT screens increases, it becomes more difficult to measure and correct for this distortion. We present a simple, highly accurate method for determining the mapping between internal coordinates and the viewing plane. It requires that an observer, using a calibration program, adjust triples of displayed points until they are collinear. A metal straightedge placed between the observer and the screen aids in this judgment. We describe the calibration of an IBM Enhanced Graphics Display in high-resolution mode (350 × 640 pixels), and illustrate how to use the estimated mapping to choose internal coordinates to draw undistorted figures that are accurate to within 0.5 pixel. The method can be used to assess or to correct the accuracy of visual displays. The method is relevant to experiments in spatial vision, spatial perception, perception of dot patterns, and any application in which geometrically accurate stimuli are required.     

A small pulse generator for calibrating EEG recording systems

A battery-powered pulse generator of uncomplicated circuit arrangement has the advantage of being easily constructed and, also, can be positioned in a confined testing area in order to simulate the low-amplitude signals of a S. It may be especially useful for EEG recording systems for small animals. In this way, the complete recording system, including connecting cables, can be calibrated, and its performance readily assessed with respect to frequency response and to susceptibility to noise pickup.     

Calibration of an eye-movement system for use in reading

A method for measuring horizontal eye movements in the msec range is described. Accurate measurement of horizontal eye movement over a linear range of 12° is achieved by processing the image of the eye illuminated with infrared light and with the head position fixed. The system has given very reliable results, and a resolution of 6 min of visual angle can be achieved with a character space of 45 min of arc. We also describe efficient numerical-data processing which allows the precise determination of the absolute position of the eye.     

A measure of agreement for use with the Holland classification system

A measure of agreement for partially ordered data is suggested that makes use of the k categories with the highest ranks, the ranks of the remaining categories being disregarded. The proposed measure is applied to the Self-Directed Search in order to evaluate its agreement with occupational preference. Other forms of agreement in the Holland classification system can also be assessed by the proposed measure. Examples are congruence and husband-wife and counselor-client agreement.     

A vocal response time system for use with sentence verification tasks

A software system for the reliable detection of vocal response onset is described. The system was designed specifically for the measurement of vocal response times to speech stimuli presented aurally in a sound field in the presence of some background noise. The response time extraction method described here is robust to masking noise and extraneous sounds that may be included in the subject’s recorded response. In addition, the response words do not have to be limited to a small set because the system is able to differentiate the onset of any speech sounds, including low-energy fricatives. The method described here may be implemented with any computer sound system because it relies only on the sound conversion clock for timing accuracy and uses postprocessing of the signal after acquisition for response extraction. The response time extraction technique as currently implemented does not recognize subject’s responses but could be incorporated into an automatic speech recognition system.     

Simulated unit pulses for calibrating

A small battery-powered instrument generates sinusoidal pulses of approximately the shape of neuronal pulses. The output consists of alternate positive and negative pulses across a 10 k ohm source resistance. Such a signal allows a quick assessment of the amplification system and indicates possible losses through shunt capacitances along the connections between S and amplifier input.     

Multiple independent identification decisions: a method of calibrating eyewitness identifications

Two experiments (N = 147 and N = 90) explored the use of multiple independent lineups to identify a target seen live. In Experiment 1, simultaneous face, body, and sequential voice lineups were used. In Experiment 2, sequential face, body, voice, and clothing lineups were used. Both studies demonstrated that multiple identifications (by the same witness) from independent lineups of different features are highly diagnostic of suspect guilt (G. L. Wells & R. C. L. Lindsay, 1980). The number of suspect and foil selections from multiple independent lineups provides a powerful method of calibrating the accuracy of eyewitness identification. Implications for use of current methods are discussed.     

A telemetric method for measuring and recording head rotations in human infants

A simple and reliable apparatus for recording directional head movements of infants is described. The technique permits unrestricted movement and avoids distress associated with mechanical head harnesses.     

An automated identification system for use with computer-controlled tasks

Monkeys of various species can use a joystick to perform a variety of computer-generated tasks. The purpose of this paper is to describe an automated system that determines which subject in a social group has completed a task. The system is based on a microchip that is easily injected into the forearm. The present paper demonstrates the technique with 1 animal that had a different chip in each arm.     

A method for obtaining an ordered metric scale

A method is presented for collecting data which will yield a scale on which the entities are ranked in preference (ordinality), the distances between the entities on the scale are ranked (ordered metric), and all combinations of the distances are ranked (higher-ordered metric). The sources drawn upon are von Neumann and Morgenstern (9), and lattice theory. An empirical example is given in which a higher-ordered metric scale is derived.I am grateful to Professor William L. Lepley (Department of Psychology) and Professor Jack R. Tessman (Department of Physics) for their critical reading of this paper. Paul Hurst and Robert Radlow participated in many discussions on the form of measurement discussed in this paper, and assisted in collecting data. I am also grateful to Professor T. C. Benton (Department of Mathematics) for certain source materials.     

A tachistoscopic software system for use in remote timesharing applications

A program is described that permits the use of an Imlac PDS-1 display computer, in conjunction with a host timeshare system, as a software-controlled tachistoscope. Alphanumeric and graphic message strings are received from the host computer over a telephone line, and are then displayed for specified periods of time in sequence. The display computer records the S’s responses and reaction time and reports this information back to the host computer for recording and analysis. The system is designed so that the burden of software development for the realization of a specific experimental plan is shifted to the large-capacity host machine, and it can utilize all of the features of standard FORTRAN as implemented on the host computer system.     

Memory for melody: infants use a relative pitch code

Pitch perception is fundamental to melody in music and prosody in speech. Unlike many animals, the vast majority of human adults store melodic information primarily in terms of relative not absolute pitch, and readily recognize a melody whether rendered in a high or a low pitch range. We show that at 6 months infants are also primarily relative pitch processors. Infants familiarized with a melody for 7 days preferred, on the eighth day, to listen to a novel melody in comparison to the familiarized one, regardless of whether the melodies at test were presented at the same pitch as during familiarization or transposed up or down by a perfect fifth (7/12th of an octave) or a tritone (1/2 octave). On the other hand, infants showed no preference for a transposed over original-pitch version of the familiarized melody, indicating that either they did not remember the absolute pitch, or it was not as salient to them as the relative pitch.     

Color-function categories that prime infants to use color information in an object individuation task

There is evidence for developmental hierarchies in the type of information to which infants attend when reasoning about objects. Investigators have questioned the origin of these hierarchies and how infants come to identify new sources of information when reasoning about objects. The goal of the present experiments was to shed light on this debate by identifying conditions under which infants’ sensitivity to color information, which is slow to emerge, could be enhanced in an object individuation task. The outcome of Experiment 1 confirmed and extended previous reports that 9.5-month-olds can be primed, through exposure to events in which the color of an object predicts its function, to attend to color differences in a subsequent individuation task. The outcomes of Experiments 2-4 revealed age-related changes in the nature of the representations that support color priming. This is exemplified by three main findings. First, the representations that are formed during the color-function events are relatively specific. That is, infants are primed to use the color difference seen in the color-function events to individuate objects in the test events, but not other color differences. Second, 9.5-month-olds can be led to form more abstract event representations, and then generalize to other colors in the test events if they are shown multiple pairs of colors in the color-function events. Third, slightly younger 9-month-olds also can be led to form more inclusive categories with multiple color pairs, but only when they are allowed to directly compare the exemplars in each color pair during the present events. These results shed light on the development of categorization abilities, cognitive mechanisms that support color-function priming, and the kinds of experiences that can increase infants’ sensitivity to color information.