Synchronizing stimulus displays with millisecond timer software for the IBM PC

A C language technique for synchronizing millisecond timer software to the appearance of the stimulus on the IBM PC’s video monitor is described. Tachistoscopic programs that use the technique can correct the mean 8.3-msec bias normally found in reported response latencies and reduce the associated error variance.     

SIMSTAT: Bootstrap computer simulation and statistical program for IBM personal computers

SIMSTAT is a computer program that provides bootstrap confidence intervals and estimates distribution parameters for 27 univariate and bivariate statistics. Because it permits variation of the bootstrap sample size, it is a convenient tool for research planning, allowing comparison of power estimates and estimator precision for various estimators and/or sample sizes. SIMSTAT also is a useful tool for studying the robustness of various statistics on real-world data and may be helpful in teaching statistical principles.     

The 3RT Test: Three reaction time tasks for IBM PC computers

The 3RT Test consists of a simple, a choice, and a conditional reaction time (RT) task. The three tasks involve comparable visual stimuli and require identical manual responses, but they differ in the complexity of cognitive processing required. The nonverbal stimuli convey commonly known meanings. Responses can be made either on the keyboard or on response keys connected to the computer’s serial port. The computer’s internal timer/counter is used for millisecond timing. The test administration program allows flexible setting of the test conditions. The data analysis program provides summary data not only for each RT task as a whole, but also for separate trial types within each task. Summary statistics include measures of variation and central value that are not affected by extreme scores. In addition to laboratory studies with normal adults, the 3RT Test is suitable for life-span developmental studies, cross-cultural comparisons, and other uses in various clinical settings.     

Evidence against late selection: stimulus quality effects in previewed displays

Strong late-selection theories of visual attention assert that when multiple stimuli belonging to familiar categories are presented, their identities are computed automatically and tagged for their locations. When selection by location is required, the identities are said to be retrieved without any need to repeat the perceptual processing. Five experiments designed to test this account are reported. All included a condition in which a display of eight characters was previewed for several hundred ms; a bar probe then designated one character the target for speeded classification. Stimulus factors that slow the character encoding process were manipulated. If selection is late, then such factors should have no effect in this condition because the probe occurs after automatic encoding is complete. There was no evidence of any such reduction in these factors' effects on reaction times or errors. The results were unchanged when catch trials with postdisplay masks were included, to discourage any optional delay of encoding. Several possible accounts are considered of how the strong late-selection model may be wrong, even if parallel encoding occurs in various situations.     

Converting scanned images for display in human experimental research on IBM or IBM-compatible computers

A program for the conversion of TIFF files of scanned images for display on IBM PCs is described. The program allows line drawings from various sources to be displayed in Turbo Pascal programs. The resultant picture files can be converted on a range of monitors, and the images displayed in different colors.     

Controlling nonverbal displays: Facial expressions and tone of voice

This study investigated the hypothesis that facial expressions are more controllable and closer to one's awareness than vocal cues. Specifically, it was suggested that nonverbal displays are a function of three factors: (a) expressiveness, or the tendency to display spontaneous nonverbal cues: (b) controllability, or the ability to voluntarily suppress or exaggerate one's spontaneous display: and (c) demeanor, or the sender's tendency to convey a particular impression regardless of his/her experienced emotion. Subjects' facial and vocal reactions to affective stimuli were recorded in a spontaneous condition or under instructions to magnify or conceal reactions to these stimuli. It was shown that information conveyed by facial expressions was best accounted for by controllability whereas information conveyed by tone of voice was best accounted for by expressiveness and demeanor.     

How to obtain near-millisecond precision on the IBM PC with visual stimuli not exceeding one printed line

Techniques are described for using an IBM PC equipped with a mouse to investigate the reading of character sequences of maximally one display line. Solutions are given to problems that arise and derive from the PC’s real-time clock, the slowness of the display, and registration of input during a test session. A program for using the techniques to study asynchronous perception of printed words is described, and a demonstration program is provided as an appendix.     

Two scenes or not two scenes: The effects of stimulus repetition and view-similarity on scene categorization from brief displays

Previous research suggests that understanding the gist of a scene relies on global structural cues that enable rapid scene categorization. This study used a repetition blindness (RB) paradigm to interrogate the nature of the scene representations used in such rapid categorization. When stimuli are repeated in a rapid serial visual presentation (RSVP) sequence (~10 items/sec), the second occurrence of the repeated item frequently goes unnoticed, a phenomenon that is attributed to a failure to consolidate two conscious episodes (tokens) for a repeatedly activated type. We tested whether RB occurs for different exemplars of the same scene category, which share conceptual and broad structural properties, as well as for identical and mirror-reflected repetitions of the same scene, which additionally share the same local visual details. Across 2 experiments, identical and mirror-image scenes consistently produced a repetition facilitation, rather than RB. There was no convincing evidence of either RB or repetition facilitation for different members of a scene category. These findings indicate that in the first 100–150 ms of processing scenes are represented in terms of local visual features, rather than more abstract category-general features, and that, unlike other kinds of stimuli (words or objects), scenes are not susceptible to token individuation failure.     

A dyadic stimulus set of audiovisual affective displays for the study of multisensory,emotional, social interactions

We describe the creation of the first multisensory stimulus set that consists of dyadic, emotional, point-light interactions combined with voice dialogues. Our set includes 238 unique clips, which present happy, angry and neutral emotional interactions at low, medium and high levels of emotional intensity between nine different actor dyads. The set was evaluated in a between-design experiment, and was found to be suitable for a broad potential application in the cognitive and neuroscientific study of biological motion and voice, perception of social interactions and multisensory integration. We also detail in this paper a number of supplementary materials, comprising AVI movie files for each interaction, along with text files specifying the three dimensional coordinates of each point-light in each frame of the movie, as well as unprocessed AIFF audio files for each dialogue captured. The full set of stimuli is available to download from: http://motioninsocial.com/stimuli_set/.     

Developing auditory stimulus control: A note on methodology

This paper concerns the problem of teaching people with intellectual handicaps to respond reliably to spoken words and other auditory instructional stimuli. We describe how microcomputer technology can be applied to implement effective auditory stimulus control shaping methods. With hardware and software currently available, it is now possible to adapt procedures that have been previously successful in stimulus control programming with visual stimuli. We describe several techniques for programming gradual stimulus changes (e.g., stimulus fading, stimulus shaping) to promote auditory discrimination learning. Teaching studies with two individuals with severe mental retardation provide illustrative applications and data supporting the feasibility and potential utility of auditory stimulus control shaping methodology.     

Controlling for stimulus dominance effects in the Fused Dichotic Words Test when predicting speech lateralization in children

A log-linear analysis (Grimshaw et al., 1994) of Fused Dichotic Words Test data was examined in a sample of 28 children with epilepsy who had undergone the intracarotid amobarbital procedure to determine the nature of speech representation. The analysis yields a measure of ear dominance (lambda*) that controls for stimulus dominance confounds. Most patients with unilateral speech obtained statistically significant ear advantages, whereas most with bilateral speech displayed no significant ear advantage. Despite controlling for stimulus dominance confounds, some of the scores from patients with left-hemisphere speech overlapped with those from patients with bilateral speech representation.     

Compound stimuli in emergent stimulus relations: Extending the scope of stimulus equivalence

Three experiments were conducted to investigate stimulus relations that might emerge when college students are taught relations between compound sample stimuli and unitary comparison stimuli using match-to-sample procedures. In Experiment 1, subjects were taught nine AB-C stimulus relations, then tested for the emergence of 18 AC-B and BC-A relations. All subjects showed the emergence of all tested relations. Twelve subjects participated in Experiment 2. Six subjects were taught nine AB-C relations and were then tested for symmetrical (C-AB) relations. Six subjects were taught nine AB-C and three C-D relations and were then tested for nine AB-D (transitive) relations. Five of 6 subjects demonstrated the emergence of symmetrical relations, and 6 subjects showed the emergence of transitivity. In Experiment 3, 5 college students were taught nine AB-C and three C-D relations and were then tested for nine equivalence (D-AB) relations and 18 AD-B and BD-A relations. Three subjects demonstrated all tested relations. One subject demonstrated the AD-B and BD-A relations but not the D-AB relations. One subject did not respond systematically during testing. The results of these experiments extend stimulus equivalence research to more complex cases.     

Verbal reports of stimulus effects on learning: Introspection revisited

The accuracy of subjects' verbal reports on the respective causal roles of relevant and irrelevant stimulus factors on learning was investigated. In two experiments, university undergraduates learned strings of letters that were either grammatically structured or unstructured (a causal variable) and either color coded or black (a salient but irrelevant variable). Results indicated that subjects reported more causal impact of color than structure on the learnability of lists, despite the fact that the latter variable and not color had an actual effect on learning. It was proposed that verbal reports of stimulus effects on one's own behavior can be regarded as a task in estimates of covariation rather than direct retrieval of memory traces.     

Inhibitory effect of a second stimulus on reaction time to a primary stimulus: a partial successful replication.

A second visual stimulus, to which no response was required, following a primary one lengthened the reaction time to the first stimulus for 25 college students. Reaction time rose as a function of the increase in the interstimulus interval. Duration time of the second stimulus did not affect this response. These results were found under a condition of stimulus-response certainty.     

Foreground:background salience: Explaining the effects of graphical displays on risk avoidance

The purpose of this research was to determine the mechanisms underlying the graphical effect identified by Stone, Yates, and Parker (1997), in which graphical formats for conveying risk information are more effective than numerical formats for increasing risk-avoidant behavior. Two experiments tested whether this graphical effect occurred because the graphical formats used by Stone et al. highlighted the number of people harmed by the focal hazard, causing the decisions to be based mainly on the number of people harmed (which we label the “foreground”) at the expense of the total number of people at risk of harm (which we call the “background”). Specifically, two graphical formats were developed that displayed pictorially both the number of people harmed and the total number at risk, and use of these display formats eliminated the graphical effect. We thus propose that the previously discussed graphical effect was in fact a manifestation of a more general foreground:background salience effect, whereby displays that highlight the number of people harmed at the expense of the total number of people at risk of harm lead to greater risk avoidance. Theoretical and practical implications are discussed.