Millisecond accuracy video display using OpenGL under Linux

To measure people’s reaction times to the nearest millisecond, it is necessary to know exactly when a stimulus is displayed. This article describes how to display stimuli with millisecond accuracy on a normal CRT monitor, using a PC running Linux. A simple C program is presented to illustrate how this may be done within X Windows using the OpenGL rendering system. A test of this system is reported that demonstrates that stimuli may be consistently displayed with millisecond accuracy. An algorithm is presented that allows the exact time of stimulus presentation to be deduced, even if there are relatively large errors in measuring the display time.     

Effects of varying the percentage of key illuminations paired with food in a positive automaintenance procedure

Three pigeons were exposed to a positive automaintenance procedure in which each trial began with a brief tone followed by the transillumination of a small central area of the response key for 10 sec. Key illumination was followed by food on 100%, 50%, 25%, 12.5%, and 0% of the trials. The effects depended on the dependent variable observed. The mean rate of responding during key illumination rapidly increased and then decreased slightly as the percentage of key illuminations paired with food increased. The number of key illuminations during which at least one response occurred increased as a negatively accelerating function of the percentage of key illuminations paired with food, and the mean latency to the first response during the key illuminations decreased as a negatively decelerating function of the percentage condition. The mean rate of sustained responding during key illumination was not systematically affected by changes in the percentage conditions.     

Perceiving minimal distinctions in ASL under normal and point-light display conditions

Perceptual confusions within 36 formationally minimal pairs of signs were assessed for native signers under two conditions of video presentation: (1) normally lighted black-and-white displays and (2) point-light displays constructed by affixing 26 points of retroreflective tape on the fingertips, back knuckles, and wrists and 1 point on the nose of the signer. Nine pairs were selected for each of the formational parameters of handshape, location, movement, and orientation. For each minimal pair, a native signer constructed and signed an ASL sentence that was syntactically and semantically appropriate for both members of the pair. Fourteen highly fluent ASL users responded by selecting a picture appropriate to the viewed sentence, thus avoiding contamination by English. For both viewing conditions, subjects discriminated the minimal pairs significantly better than chance. Performance was better (1) when location or orientation differentiated the signs than when movement or handshape did and (2) in normal lighting than in the point-light displays. With the point/light displays, discrimination of location, movement, and orientation was poorer and handshape discrimination was at chance. The discussion considers (1) the confusion of signs in the absence of linguistic redundancy, (2) the effectivenese of the point-light configurations as “minimal cues” for the contrasts, and (3) the efficacy of using these point-light configurations to reduce the information in ASL to a narrow bandwidth.     

Development and validation of a measure of display rule knowledge: the display rule assessment inventory

As one component of emotion regulation, display rules, which reflect the regulation of expressive behavior, have been the topic of many studies. Despite their theoretical and empirical importance, however, to date there is no measure of display rules that assesses a full range of behavioral responses that are theoretically possible when emotion is elicited. This article reports the development of a new measure of display rules that surveys 5 expressive modes: expression, deamplification, amplification, qualification, and masking. Two studies provide evidence for its internal and temporal reliability and for its content, convergent, discriminant, external, and concurrent predictive validity. Additionally, Study 1, involving American, Russian, and Japanese participants, demonstrated predictable cultural differences on each of the expressive modes.     

Search through a sequentially presented visual display

Several paradoxes in the visual information processing literature are reviewed. Two experiments utilizing a sequential presentation technique suggested a two-stage model of visual search in which a parallel initial stage guides the operation of a slower serial discrimination stage. A computer simulation provided a good quantitative fit to the results of both experiments. The two-stage model shows how the paradoxes may be resolved as well as providing a framework for integrating results from visual search and spatial selective attention research.     

Information transmission with a multifinger tactual display

In this work, the tactual information transmission capabilities of a tactual display designed to provide stimulation along a continuum from kinesthetic movements to cutaneous vibrations are assessed. The display is capable of delivering arbitrary waveforms to three digits (thumb, index, and middle finger) within an amplitude range from absolute detection threshold to about 50 dB sensation level and a frequency range from dc to above 300 Hz. Stimulus sets were designed at each of three signal durations (125, 250, and 500 msec) by combining salient attributes, such as frequency (further divided into low, middle, and high regions), amplitude, direction of motion, and finger location. Estimated static information transfer (IT) was 6.5 bits at 500 mseC., 6.4 bits at 250 mseC., and 5.6 bits at 125 msec. Estimates of IT rate were derived from identification experiments in which the subject’s task was to identify the middle stimulus in a sequence of three stimuli randomly selected from a given stimulus set. On the basis of the extrapolations from these IT measurements to continuous streams, the IT rate was estimated to be about 12 bits/seC., which is roughly the same as that achieved by Tadoma users in tactual speech communication.     

Distance judgments under different size-information conditions

Seventy-two Ss judged the absolute distance of a target presented without distance cues other than retinal size and assumed size. The method by which E communicated information about the size of a 3-in. target had a significant effect on the magnitude of the discrepancy between judged distance and the perceived distance required by the size-distance invariance hypothesis. In order of increasing effectiveness in producing distance judgments meeting invariance requirements were: size information in the form of verbally communicated metric units, size information communicated by labeling the target with the name of a familiar object, and size information in the form of a visual representation.     

Discrimination of painting style and quality: pigeons use different strategies for different tasks

Birds have visual cognition as well developed as humans. Sometimes, the birds show visual discrimination similar to humans, but the birds may use different cues. Previous reports suggest that global configuration cues are salient for humans, whereas local elemental cues are salient for pigeons. I analyzed the discriminative behavior of pigeons with scrambled images because scrambled images keep the local elemental cues of the original images but lose the global configuration cues. If pigeons use local elemental cues, then, they should show transfer of discrimination from the original images to their scrambled images and also transfer from the scrambled images to their original images. In Experiment I, I trained pigeons on painting style discrimination (Japanese paintings vs. Western impressionist paintings) using either the original or scrambled images and found that the pigeons showed bidirectional transfer. In Experiment II, I trained pigeons on discrimination of “good” versus “bad” paintings using children’s paintings. The birds showed poor transfer from the original images to their scrambled images and vise versa. Thus, the pigeons discriminated good and bad paintings based mostly on global configuration cues in this case. These results suggest that the pigeons use different cues for different discriminations.     

Recognizing the sex of a walker from a dynamic point-light display

The sex of human walkers can be recognized without familiarity cues from displays of pointlight sources mounted on major joints. Static versions of these abstract displays do not permit accurate recognition of sex. Variation in the degree of armswing or in walking speed generally interferes with recognition, except that faster speeds are associated somewhat with improved recognition of females. Lights on upper-body joints permit more accurate guesses than do Lights on lower-body joints, but identification is possible even from minimal displays, with lights placed only on the ankles. No feedback was given to observers. Confidence judgments of sex relate to the accuracy of responses in a manner that suggests that viewers know what they are doing.     

The slide projector as a computer-operated visual display

Advantages and method are presented for using the slide projector in a computer-operated visual display system.     

An alphanumeric display program for a PDP-8

Alphanumeric and special characters composed of 5 by 7 dot matrices can be displayed on a cathode ray tube by use of a program written for the PDP-8 family of computers. The CRT surface is specified to contain up to 32 rows with up to 32 characters per row. The 35 dots defining each character require 1.5 msec to generate. Every possible arrangement of spatial and temporal organization among and between strings of characters can be created by simple parameter specification before each trial. The program is designed to operate with a minimal 4k-memory computer configuration, with no special hardware other than an oscilloscope display. The program also permits efficient on-line operation so that an entire experiment can be run quickly and efficiently without further programming. A large number of examples are detailed, and operating procedures are specified.     

Eye movements under different rehearsal strategies.

Eye movements were recorded while subjects studied lists of simultaneously presented words. The 24 subjects in the storage group studied for immediate recall, and the 24 subjects in the coding group studied primarily for a later, final recall. Those subjects in the coding group had longer eye fixations and fewer regressions than did subjects in the storage group. In addition, the subjects in the coding group recalled fewer words in immediate recall and more words in final recall than did the subjects in the storage group. These results were interpreted as supporting the elaboration hypothesis of coding in rehearsal, which states that coding into long-term store consists of rehearsing both old and new information in short-term store. The results did not support the concentration hypothesis, which states that coding into long-term store consists of intensively rehearsing a smaller number of items than rehearsed under a storage strategy. The eye movement data also indicate that subjects read about twice as many words as they overtly rehearse.     

Loading mobile phones in a multi-option society

As mobile phone saturation increases, operators find it harder and harder to differentiate themselves in the marketplace. Telecommunications companies have had to develop strategies as quickly as the industry has developed, and in recent years have found themselves increasingly moving away from their core market of voice service provision to becoming anything from fashion brands to putative multimedia companies. From the consumer's perspective, Peter Gross and Stefan Bertschi discuss how a customer navigates such a 'multi-option' society. Bewildered by choices--not just in service level and provision but in the way these products are coded with brands that suggest identities and cultural behaviour--how is a consumer to relate to such a plurality of options?     

Motion-induced overestimation of the number of items in a display

Subjects were asked to report the number of items in a display as the items moved along a circular path around the fixation point. As the rotation speed increased, the apparent number of items also increased. This motion-induced overestimation (MIO) effect was investigated in three experiments. In the first experiment, the effect of rotation speed and set size was explored with an enumeration task. The overestimation error increased with an increase in speed or number of items in the display. In the second experiment, we used an adjustment paradigm to measure the speed threshold of MIO effect onset. Temporal rate of the display, which was defined as product of rotation speed and the number of rotating items, was the determining factor of MIO onset. In the third experiment, moving items were marked with different colours. Surprisingly, the number of perceived items was still overestimated even though the number of perceived colours was not.