Charles E. Collyer

Preferred rates of repetitive tapping and categorical time production

In a constrained finger-tapping task, in which a subject attempts to match the rate of tapping responses to the rate of a pacer stimulus, interresponse interval (IRI) was a nonlinear function of interstimulus interval (ISI), in agreement with the results of Collyer, Broadbent, and Church (1992). In an unconstrained task, the subjects were not given an ISI to match, but were instructed to tap at their preferred rate, one that seemed not too fast or too slow for comfortable production. The distribution of preferred IRIs was bimodal rather than unimodal, with modes at 272 and 450 msec. Preferred IRIs also tended to become shorter over successive sessions. Time intervals that were preferred in the unconstrained task tended to be intervals that were overproduced (IRI > ISI) when they were used as ISIs in the constrained task. A multiple-oscillator model of timing developed by Church and Broadbent (1990) was used to simulate the two tasks. The nonlinearity in constrained tapping, termed theoscillator signature, and the bimodal distribution in unconstrained tapping were both exhibited by the model. The nature of the experimental results and the success of the simulation in capturing them both provide further support for a multiple-oscillator view of timing.

Categorical time production : evidence for discrete timing in motor control

Subjects performed a repetitive manual tapping task, attempting to match a given rate of auditory stimulus pulses, first with the pulses audible (synchronization) and then with the pulses turned off (continuation). In different sessions, the interstimulus interval (ISI) was selected from the range 175 to 825 msec in steps of 25 msec, with different ISI values presented in a random order. Across this range of ISI conditions, interresponse intervals (IRIs) exhibited alternating positive bias (too slow) and negative bias (too fast). We interpret this pattern of bias in terms of a discrete, or categorical, timing mechanism in motor timing. Categorical time production can be viewed as extending our conception of the timekeeper in Wing’s (Wing’ & Kristofferson, 1973a, 1973b) two-process model of motor timing and may be related to the system of multiple clocks proposed by Kristofferson (1980) to explain a categorical pattern of variability measures in duration discrimination.

Discrimination of spatial and temporal .: intervals defined by three light flashes: Effects of spacing on temporal judgments and of timing on spatial judgments

Observers were presented stimulus patterns consisting of a sequence of three laterally displaced light flashes, which defined two spatial intervals and two temporal intervals. The position and time of the second flash were varied factorially, and observers were asked to make relative judgments of either the two spatial intervals or the two temporal intervals. “Induction” effects of stimulus timing on spatial judgments and of stimulus spacing on temporal judgments were both found; however, the directionality of these effects differed between subjects. The results are inconsistent with the hypothesis, derived from previous findings, that such effects are determined primarily by a tendency toward perceiving constant velocity of apparent motion; it is proposed that the directionality of the induction effects is determined largely by the strategy adopted by the observer for combining spatial and temporal stimulus information.

Adding Graphics to Dynamic Message Sign Messages

A human factors study assessed the effects of adding graphics to dynamic message sign (DMS) messages. Two approaches employed in the assessment—a questionnaire survey and a video-based driving simulation experiment—are reported here along with the findings. The questionnaire surveyed drivers’ preferences concerning the addition of graphics to a text message, the color of the message, alternative graphic images, placement of the graphic image, image contrast, flashing, and the framing of graphic images. One hundred and twenty-seven subjects from Rhode Island participated in the survey. Statistical analysis of survey results showed strong preference for graphic-aided messages over text-only messages; amber-color messages over green- and red-color messages; and messages with graphic on the left side over others. The analysis also identified specific graphics to accompany certain text messages. Based on the survey results, a video-based driving simulation experiment was designed to test drivers’ responses to selected DMS messages surveyed in the questionnaire. Forty-eight subjects from different age groups with different native language backgrounds took part in the experiment. Results of the experiment showed that graphic-aided messages displayed in amber or green were responded to significantly faster than other settings. Older drivers’ responses were slower and less accurate than others; however, their responses improved significantly when the DMS messages were enhanced by graphics. It was also found that graphic-aided DMS messages helped improve the responses of non-native-English-speaking drivers.

A motor timing experiment implemented using a musical instrument digital interface (MIDI) approach

The musical instrument digital interface (MIDI) offers a way for perception and behavior researchers to implement high-quality experiments using inexpensive, commercially available hardware and software. We describe the MIDI and illustrate its applicability to research using a replication of the oscillator signature finding reported recently by Collyer, Broadbent, and Church (1992, 1994).

Typology of violence derived from ratings of severity and provocation.

Two exploratory studies examined ratings of the severity of violence of several behaviors. In Study 1, a very consistent ordering of the behaviors by severity was obtained from two groups of participants. The stated justification for the behaviors was manipulated, and both mitigation and aggravation effects were observed. Study 2 found that essentially the same ordering of behaviors could be obtained in a provocation-rating task, and that both the severity ratings and the provocation ratings yielded four interpretable types of violence upon factor analysis: more severe physical (V1), less severe physical (V2), more severe nonphysical (V3), and less severe nonphysical (V4). Individual profiles of severity ratings across these four types yielded two interpretable groupings of participants upon cluster analysis: a violence-sensitive group and a violence-tolerant group. The violence-tolerant group had lower severity ratings for three of the four types of violence. These empirical distinctions help to illuminate what appear to be different meanings of the term violent for different behavior categories and for different individuals.

Correction of errors in scientific research

Four ways to reduce scientific errors are by tests of equipment and programs, examination of results, peer review, and replication. This article describes various types of errors that may occur and procedures available for the prevention and correction of both unintentional and intentional errors in experiments that use computer programs to generate the stimuli, record the responses, or analyze the data. We describe a case study of a particular experiment that produced a result that has been found to be erroneous. The case study provides additional evidence of the essential importance of replication for the identification and elimination of scientific error.

Individual Differences in Sensitivity to Violence

A survey of university students explored correlates of sensitivity to violence, defined as a persons average rating of the severity of violence of several behaviors. The 79 women were somewhat more sensitive than the 39 men. Sensitivity was associated with the tendency to describe oneself as violence sensitive or violence tolerant, with the persons manner of defining the concept of violence, and with the tendency to include verbal abuse and inaction as possible forms of violence. Sensitivity was not clearly associated with some other variables, such as attitudes toward bullying and acceptability of hunting. The potential utility of measuring sensitivity to violence, and further work suggested by these findings, are discussed.

Is there a threshold for mental rotation

A threshold-like nonlinearity was found in a mental rotation experiment designed for relatively heavy sampling of small angular disparities. The value of the threshold in this experiment appeared to be around 15°. Results of a control experiment were that subjects easily discriminated orientations differing by as little as 6° using the same stimulus materials. A threshold hypothesis represents one way to think about the flexibility and limitations of mental rotation performance.

Psychology of the scientist: LXIII. Perceiving scattergrams: is visual line fitting related to estimation of the correlation coefficient?

Visual line fitting and direct estimation of the correlation coefficient were carried out by 50 subjects using computer-generated scattergrams as stimuli. In visual line fitting, slopes of visual lines were generally greater than the corresponding regression slopes, in agreement with the hypothesis that visual lines are placed so as to bisect the cloud of displayed points at the clouds major axis rather than to approximate a regression line. Subjects tended to underestimate the correlation coefficient, scaling their judgments of linear structure somewhat more as if they were judging the coefficient of determination. With the actual degree of linear structure partialed out, there were no strong relationships between measures of visual line fitting and measures of estimation. While both of these tasks offer quickly-obtained correlates of linear structure in scattergrams, users should be aware of their biases. We suggest that visual lines do not approximate regression lines very well and estimates of correlation do not approximate the correlation coefficient very well, because the perceptual processes involved perform operations other than regression and correlation. In the present data, these operations appeared to be independent of each other.