Programs for visual psychophysics on the Amiga: A tutorial

A typical psychophysical experiment presents a sequence of visual stimuli to an observer and collects and stores the responses for later analysis. Although computers can speed up this process, paint programs that allow one to prepare visual stimuli without programming cannot read responses from the mouse or keyboard, whereas BASIC and other programming languages that allow one to collect and store observer’s responses unfortunately cannot handle prepainted pictures. A new programming language called The Director provides the best of both worlds. Its BASIC-like commands can manipulate prepainted pictures, read responses made with the mouse and keyboard, and save these on disk for later analysis. A dozen sample programs are provided.     

Visual stimuli on the Commodore Amiga: A tutorial

The Commodore Amiga home microcomputer, together withDeLuxePaint, a commercial software package, can generate many useful visual stimuli, including random-dot stereograms, apparent motion, texture edges, aftereffects from dimming and brightening, motion aftereffects, dynamic random noise, and drifting and counterphase gratings. Videotapes can readily be made of these displays. No programming experience is necessary.     

Frequency synthesis with the Commodore Amiga for research on perception and memory of pitch

The potential of the Commodore Amiga as a digital synthesizer for research and demonstration in psychoacoustics and memory is discussed. Economy, ease of use, flexibility, portability, and accuracy outweigh disadvantages of narrow bandwidth, narrow dynamic range, and storage limitations for many applications encountered in pilot research and education. The Amiga also bears serious consideration for psychoacoustic studies requiring frequencies below 4000 Hz and modest signal-to-noise ratio, as exemplified by an implementation for research in absolute judgment, similarity scaling, and sequential pattern tracking.     

Competition for consciousness among visual events: the psychophysics of reentrant visual processes

Advances in neuroscience implicate reentrant signaling as the predominant form of communication between brain areas. This principle was used in a series of masking experiments that defy explanation by feed-forward theories. The masking occurs when a brief display of target plus mask is continued with the mask alone. Two masking processes were found: an early process affected by physical factors such as adapting luminance and a later process affected by attentional factors such as set size. This later process is called masking by object substitution, because it occurs whenever there is a mismatch between the reentrant visual representation and the ongoing lower level activity. Iterative reentrant processing was formalized in a computational model that provides an excellent fit to the data. The model provides a more comprehensive account of all forms of visual masking than do the long-held feed-forward views based on inhibitory contour interactions.     

Real-time color-frame animation for visual psychophysics on the Macintosh computer

Psychophysical experiments involving moving stimuli require the rapid presentation of animated sequences of images. Although the Macintosh computer is widely used as a color graphics computer in research laboratories, its animation capabilities are generally ignored because of the speed limitations of drawing to the screen. New off-screen color graphics structures help to avoid the speed limitations so that real-time color or gray-scale visual motion stimuli may be generated. Precomputed animation frames are stored in off-screen memory and then rapidly transferred to the screen sequentially. The off-screen graphics structures may also be saved to disk in “Picture” form as “resources” for later retrieval and playback, allowing the experimenter to build in advance a collection of moving stimuli to use in future experiments. Code examples in the C programming language are provided, and the relative strengths and weaknesses of Macin-tosh color-frame animation for psychophysical experimentation are discussed.     

Using hardware interrupts for timing visual displays and reaction-time key interfacing on the Commodore 64

The use of hardware interrupts for presenting and timing visual displays and for controlling reaction timing on the Commodore 64 is described. The three sources of interrupts discussed are reaction-time keys interfaced through the user port to on-board hardware timers, the alarm of the 60-Hz real-time clocks, and the video raster. In a demonstration program, these interrupts are used to measure display durations, to change screen displays, and to coordinate the onset of reaction timing with the onset of screen changes. In addition, an externally generated interrupt caused by a keypress is used to control reaction timing independently of CPU operations.     

Measurement of directional lever response reaction time with the Commodore 64

Routines are described for timing directional lever responses with the Commodore 64 micro-computer. Millisecond reaction timing is carried out with on-board hardware clocks, and lever responses are detected by monitoring the position of a joystick interfaced to a controller port. In a demonstration program, a machine code subroutine is used to measure the reaction times of lever responses in a spatial relations task. In addition, modifications to the demonstration program are suggested to adapt it for use with other tasks.     

Comment on "Competition for consciousness among visual events: the psychophysics of reentrant visual processes" (Di Lollo,Enns, & Rensink, 2000)

V. Di Lolo, J. T. Enns, and R. A. Rensink (2000) reported properties of masking that they claimed were inconsistent with all current models. The current authors show, through computer simulation, that many current models can account for V. Di Lollo et al.'s (2000) data. Although V. Di Lollo et al. (2000) argued that their data could be accounted for only with models that incorporate reentrant processing, the current authors show that reentrant processing is not necessary.     

Studying visual search using systems factorial methodology with target-distractor similarity as the factor

Systems factorial technology (SFT) is a theory-driven set of methodologies oriented toward identification of basic mechanisms, such as parallel versus serial processing, of perception and cognition. Studies employing SFT in visual search with small display sizes have repeatedly shown decisive evidence for parallel processing. The first strong evidence for serial processing was recently found in short-term memory search, using target-distractor (T-D) similarity as a key experimental variable (Townsend & Fifi?, 2004). One of the major goals of the present study was to employ T-D similarity in visual search to learn whether this mode of manipulating processing speed would affect the parallel versus serial issue in that domain. The result was a surprising and regular departure from ordinary parallel or serial processing. The most plausible account at present relies on the notion of positively interacting parallel channels.     

An approach to combine the logistic threshold model of psychophysics with the Bradley-Terry-Luce models of choice theory

The paper presents a straightforward extension of the Bradley-Terry-Luce model (BTL model) that can be derived from the logistic threshold model of psychophysics which assumes that psychometric functions are logistic probability functions. It is shown that (under weak side conditions) the logistic threshold model is a submodel of the extended BTL model. Moreover, representation and uniqueness theorems are proven that provide some evidence that the extended BTL model is a useful and widely applicable generalization of the ordinary BTL model. Finally, the logistic shape of the psychometric function is derived from axioms about binary choice probabilities. This characterization of the logistic threshold model can replace goodness of fit tests for the logistic probability distribution.     

Response latency in visual search with redundancy in the visual display

Two experiments were run to investigate the effects of redundant display items upon response latency in a visual search task. In the first study, Ss searched five-letter displays for a predesignated critical letter. Both critical and noncritical letters could be repeated in the displays. Mean response latency decreased markedly with increasing redundancy in the critical letter and was affected to a lesser extent by redundancy in the noncritical letters. In the second study, Ss were required to detect the presence of redundant letters in displays of from two to five letters, first with no information as to what letter might be repeated, then with knowledge of which letter would be repeated if the display contained a redundant letter. Response latencies in the former case were much slower than in the latter. The implications of these findings for current views of visual information processing were discussed.     

Attenuating the visual suffix effect with color

In previous studies using a short-duration visual presentation (200-340 msec), presentation of a different colored suffix did not attenuate the visual suffix effect. In Experiment 1, color attenuated the suffix effect for a longer duration visual presentation (approximately 3-4 sec) during which the subject engaged in articulatory suppression to prevent auditory recoding. Experiments 2 and 3 confirmed that color does not attenuate the suffix effect for the short-duration presentations. In Experiment 4, recall of a long-duration presentation was not improved when the last digit was a different color, suggesting that the different color of the suffix improves recall by allowing the suffix to be excluded from visual short-term memory. The attenuation by color is consistent with the hypothesis that preattentive grouping governs the entry of information into visual short-term memory.     

Schedules using noxious stimuli. III. Responding maintained with response-produced electric shocks

Responding was maintained in two squirrel monkeys under several variations of a 10-min fixed-interval schedule of electric shock presentation. The monkeys were first trained under a 2-min variable-interval schedule of food presentation, and then under a concurrent schedule of food presentation and shock presentation. In one monkey, when shocks (12.6 ma) followed each response during the last minute of an 11-min cycle ending with a timeout period, responding was increased during the first 10 min and suppressed during the last minute of each cycle. When the shock schedule was eliminated, both the enhancement and suppression disappeared, and a steady rate of responding was maintained under the variable-interval schedule. When the food schedule was eliminated, the shock schedule maintained a characteristic fixed-interval pattern of responding during the first 10 min, but suppressed responding during the last minute of each cycle. The fixed-interval pattern of responding was maintained when the timeout period was eliminated and when only one shock could occur at the end of the cycle. In the second monkey, responding under the concurrent food and shock schedule was suppressed when responses produced shocks after 3-min. Under an 11-min cycle, responding continued to be maintained at increasing shock intensities. When the food schedule was eliminated, a fixed-interval pattern of responding was maintained under a 10-min schedule of shock presentation (12.6 ma). Whether response-produced electric shocks suppressed responding or maintained responding depended on the schedule of shock presentation.     

The development of visual and auditory selective attention using the central-incidental paradigm

Analogous auditory and visual central-incidental learning tasks were administered to 24 second-, fourth-, and sixth-grade and college-age subjects to study the effects of modality of presentation on memory for central and incidental stimulus materials. There was no strong evidence to indicate that modality of presentation was an important factor in the development of selective attention. Central task learning increased with age for both auditory and visual presentations; incidental learning declined at the oldest age level for both auditory and visual tasks. The serial position analysis revealed that the observed developmental increase in recall performance was due primarily to differences in the initial serial positions. The use of active strategies for focusing attention on the relevant stimulus materials seemed to be the crucial determinant of level of performance.     

Appetitive learning using visual conditioned stimuli in the pond snail, lymnaea

Feeding can be conditioned in the pond snail Lymnaea stagnalis to two different visual stimuli (a black panel or a 5-mm black and white check surround) by pairing the potential conditioned stimulus (CS) with sucrose. Exclusion of chemical cues (associated with differences between the water in home tank and that in training apparatus) that could serve as CS is important for successful visual conditioning. A featureless gray surround, used as an alternative to the check (to which it was matched in luminance) in counterbalanced training designs, was discriminated from the check, showing that resolution (for which the eyes would be necessary) was occurring. The gray surround was largely ineffective as a CS. Single-trial learning was possible with the black panel, but not with the check; it is argued that this may be due to lack of prior experience of stimuli like the check. Conditioning of feeding has now been obtained in Lymnaea to chemical, tactile, and visual cues, opening the way to comparative studies of the neural circuitry underlying appetitive conditioning in different senses, so far explored in Lymnaea only for tactile CS. Such comparative studies are as yet largely lacking in invertebrates.     

Effective CCTV and the challenge of constructing legitimate suspicion using remote visual images

This paper compares the effectiveness of public CCTV systems according to meta‐reviews, with what might be expected based upon theoretical predictions. The apparent gulf between practice and prediction is explored in the light of the challenges faced by CCTV operators in terms of effective target selection. In addition, counter‐intuitive reactions by members of the public to situational symbols of crime deterrence may also undermine the efficacy of CCTV. Evidence is introduced and reviewed that suggests CCTV operators may employ implicit profiles to select targets. Essentially, young, scruffy males who appear to be loitering are disproportionately targeted compared with their base rate use of surveyed areas. However, the extent to which such a profile is diagnostic of criminal intent or behaviour is unclear. Such profiles may represent little more than ‘pattern matching’ within an impoverished visual medium. Finally, suggestions for future research and effective CCTV operator practice are offered in order to improve target selection. Copyright © 2008 John Wiley & Sons, Ltd.     

The time course of argument reactivation revealed: using the visual world paradigm

Previous research has found that the single argument of unaccusative verbs (such as fall) is reactivated during sentence processing, but the argument of agentive verbs (such as jump) is not (Bever & Sanz, 1997; Friedmann, Taranto, Shapiro, & Swinney, 2008). An open question so far was whether this difference in processing is caused by a difference in thematic roles the verbs assign, or a difference in the underlying syntactic structure. In the present study we tease apart these two potential sources. In order to achieve this, we included a set of verbs (like sparkle) which are equal to unaccusative verbs in the thematic role they assign to their argument, but equal to agentive verbs in the syntactic status of their argument (henceforth mixed verbs). As a method we used the visual world paradigm as this enables us to measure processing of the sentences continuously. This method also allowed us to test another hypothesis, namely the hypothesis that not only the argument of unaccusative verbs is reactivated during processing, but also the argument of agentive verbs. This reactivation is expected as the result of integrating the verb and its argument into one representation. In our experiment, participants listened to sentences including one of the three types of verbs. While listening, they viewed a visual display in which one of four objects was strongly related to the argument of the verb (wood-saw). The gaze record showed that the eyes moved to the related object (saw) upon presentation of the argument (wood). More interestingly, the eyes moved back to the related object upon presentation of the verb (fell). We found that looks to the related object increase only late after verb offset for unaccusative verbs, replicating the findings of previous research. We also found a rise in looks to the related object in agentive verbs, but this rise took place much earlier, starting slightly after verb onset. Finally, we found that mixed verbs pattern in processing with agentive verbs. We conclude that the argument of the verb is always reactivated, independent of verb type. In addition, the timing of integration differs per verb type and depends on the syntactic status of the argument and not on the thematic role that is assigned to the argument.     

On the possible dangers of using horizontal word displays in visual field studies

In a sample of 100 four-letter words, there was more information about the identity of the words in the first letter than in the last letter. However, information asymmetry did not correlate with visual field differences in a lexical decision study. It therefore may be possible to use horizontally displayed short words in visual field studies without being concerned about peripheral factors. Different factors affect the recognition of vertical and horizontal displays, and the use of vertical displays is not advised.     

Studying visual attention using the multiple object tracking paradigm: A tutorial review

Human observers are capable of tracking multiple objects among identical distractors based only on their spatiotemporal information. Since the first report of this ability in the seminal work of Pylyshyn and Storm (1988, Spatial Vision, 3, 179–197), multiple object tracking has attracted many researchers. A reason for this is that it is commonly argued that the attentional processes studied with the multiple object paradigm apparently match the attentional processing during real-world tasks such as driving or team sports. We argue that multiple object tracking provides a good mean to study the broader topic of continuous and dynamic visual attention. Indeed, several (partially contradicting) theories of attentive tracking have been proposed within the almost 30 years since its first report, and a large body of research has been conducted to test these theories. With regard to the richness and diversity of this literature, the aim of this tutorial review is to provide researchers who are new in the field of multiple object tracking with an overview over the multiple object tracking paradigm, its basic manipulations, as well as links to other paradigms investigating visual attention and working memory. Further, we aim at reviewing current theories of tracking as well as their empirical evidence. Finally, we review the state of the art in the most prominent research fields of multiple object tracking and how this research has helped to understand visual attention in dynamic settings.