Leonard E. Ross

Saccade latency and warning signals: Stimulus onset, offset, and change as warning events

Two experiments investigated saccade latency to a peripheral target under various warning signal conditions. In Experiment I, the effects of warning stimulus onset, change, and two offset conditions were compared at warning intervals of 0, 100, 300, and 600 msec. Warning stimulus onset, change, and offset were all effective in reducing saccade latency as compared to a no-warning control condition, but warning stimulus offset resulted in shorter saccade latency than onset or change at all warning intervals. Experiment 2 compared onset and offset warning conditions at −300-, −250-, −200-, −150-, −100-, −50-, 0-, and 50-msec intervals. Responses following onset were slower than those following offset at the latter five intervals, while warning onset resulted in slower saccades than no-warning control conditions at −150-, −100-, and −50-msec intervals. These results indicate that the onset of a visual warning signal can have an interfering effect on the programming or execution of a saccade.

Saccade latency and warning signals: Effects of auditory and visual stimulus onset and offset

Previous studies have found that a nonspecific visual event occurring at the fovea 50–150 msec after the onset of a peripheral target delayed the initiation of the saccade to that target. The present studies replicated and extended this finding by studying the effects of both visual and auditory warning signals, by examining the effects of onset and offset warning on manual response latency, and by investigating the effects of presenting the warning events in the periphery of the visual field. The results indicated that the interfering effects occur with visual but not auditory stimuli, with saccades but not motor responses, and when the visual warning event occurs either foveally or in the subject’s periphery. Implications for the processes involved are discussed.

Saccade latency in children and adults: effects of warning interval and target eccentricity.

Abstract Saccadic response latency to the onset of an eccentric target was studied in children (mean age = 8.7) and adults. The independent variables investigated were fixation-light offset to target-light onset warning interval (0, 100, 300, and 600 msec) and target eccentricity (5° or 15°). Both children and adults showed shorter saccade latencies under warning-interval conditions. Children were found to have longer latencies than adults with 0 or 100 msec warning intervals but to respond with as short or shorter latencies with 300 or 600 msec warning intervals. Target eccentricity effects did not interact with age, and occurred only with a lower target intensity. Children defined as poor readers could initiate a response as quickly as good readers but were less able to maintain fixation-light fixation prior to target onset.

Laterality differences and practice effects under central backward masking conditions

Two experiments were conducted to examine laterality differences and practice effects under various central backward masking conditions. Critical stimulus onset asynchrony (SOA) was determined for subjects on 3 consecutive days using single letters as target stimuli (TS) and a pattern masking stimulus (MS). There was a right visual field (RVF) advantage on Day 1 but no difference between the visual fields on following days. The decline in the RVF advantage appeared to be dependent upon prior experience with laterally located letters, to be independent of initial experience with a particular set of letters, and to be more pronounced for females than for males. In addition, large improvements in performance were found, particularly between the first and second testing sessions. These practice effects were discussed in terms of the possible development of strategies for enhancing TS features or attenuating MS features.

Latency and accuracy characteristics of saccades and corrective saccades in children and adults.

Abstract Accuracy and latency characteristics of the first saccade to a target together with the frequency and latency of corrective saccades were studied in children (mean age = 8.5) and adults. The independent variables manipulated were fixation-light offset to target-light onset warning interval (0 and 300 msec) and the presence and location of nontarget stimuli. Although saccade accuracy was significantly affected by nontarget lights, children could respond as accurately as adults and, in replication of previous findings, as quickly when a 300 msec warning interval was given. No speed-accuracy trade off was found for either group as a function of the warning signal condition. Children were as likely to make corrective saccades as adults, but did so with a significantly longer latency. Corrective saccade latencies were greater when a change in direction was required but this effect did not interact with age.

Acquisition and differential conditioning of the eyelid response in normal and retarded children

Abstract Thirty-two retarded and 32 normal children matched on MA ( X = 84 months) were Ss in a classical eyelid conditioning study which included three phases of conditioning: single-cue acquisition, differential conditioning, and differential-conditioning reversal. Two CS-UCS intervals (ISIs), 500 and 800 milliseconds, were used. Acquisition performance was dependent upon ISI with the normal 800-millisecond group superior to both of the retardate groups and the normal 500-millisecond group. In differential conditioning both retardate ISI groups and the normal 800-millisecond group responded differentially but only the normal 800-millisecond Ss showed evidence of a learned discrimination. Neither normals nor retardates reversed their differential responding during the reversal phase. These results were in contrast to those obtained from college students run under similar procedures. College Ss showed increasing differential conditioning with both ISIs and good discrimination reversal under the 800-millisecond ISI condition. The results indicated (a) that comparison of the general “condition-ability” of normal and retarded children is of questionable value, with the issue of most importance being the differential effects of conditioning parameters on the conditioning performance of the IQ populations; and (b) that the processes necessary for successful differential conditioning and reversal are present in decreasing degree in college adults, normal children and retarded children.

A developmental study of attention to cue redundancy introduced following discrimination learning

Abstract Following original learning (OL) of a two-choice simultaneous visual discrimination problem by second and sixth grade Ss, the cues of the elevant and irrelevant dimensions were made 100% redundant during a 40 trial overtraining (OT) period. A control group received 40 OT trials without the redundancy. The effects of the redundancy pairing were assessed by a subsequent learning problem in which the only relevant cues were those which had been irrelevant in OL. For half the experimental Ss the OL-irrelevant cue which had been paired with the OL-positive cue during overtraining was made positive, while for the other half the cue paired with the negative OL stimulus was made positive. The data indicated that the redundancy period resulted in both instrumental response strength to the OL irrelevant cues, and a response to the dimension represented by them. Relative transfor effects for the two grade levels supported the interpretation that during the redundancy phase the younger children attended to the previously irrelevant stimuli more, i.e., “focused” on OL relevant stimuli less, than was the case with the older children. In a second study identical procedures were followed except that the correct and incorrect stimuli were identified for the S before the OL period began. The results for second grade Ss suggested that there might be decreased dimensional responding to the previously irrelevant cues during OT under these OL-instructed conditions.

Young drivers' evaluation of driving impairment due to alcohol

Ninety-six college students, 18-20 years of age, were selected from three drinking categories (abstain-light, moderate, and heavy) based on their self-reported drinking habits. Subjects rated the relative importance of three driving components (attention, control/maneuvering, and emergency responses) for safe driving and the impairment each component and overall driving ability would sustain after driver drinking. Impairment ratings were made of the effects of drinking the number of drinks that would have resulted in the rater having blood alcohol concentrations (BACs) of .05%, .10%, and .15%. Subjects also estimated the number of drinks that they could consume in one hour and then safely drive after after different time periods, the time they should wait before driving after drinking various amounts of alcohol, and the number of beer, wine, wine cooler, and whiskey drinks that would cause them to reach a .10% BAC. While the driving components were rated to be of approximately equal importance for safe driving, the emergency responses component was judged to be more impaired following alcohol consumption than any of the other components, or overall driving ability. Heavy drinkers judged that there was significantly less driving impairment due to alcohol than did light or moderate drinkers in the case of overall driving ability and all of the driving components except emergency responses. Heavy drinkers also judged it safe to consume a number of drinks before driving that would result in higher mean BACs than those of light and moderate drinkers. Both drinking category and gender differences were found in the estimated BAC values that would have occurred at the time of driving after waiting periods judged by subjects to be sufficient for safe driving.

Saccadic Eye Movements of Children and Adults to Double-Step Stimuli

The programming and reprogramming of oculomotor responses to double-step and single-step targets was investigated in 5-6-year-old and 10-12-year-old children and in adults. The independent variables in Experiment 1 were intertarget interval (50, 100, 150, and 200 msec) and target location. The number of trials on which a saccade was made to both first and second targets increased with age and intertarget interval, but the two factors did not interact. On trials where responses were made only to the second target, the children responded slower than the adults but showed generally similar patterns of response latencies. In Experiment 2, a warning signal was presented 0, 100, or 300 msec prior to the first target. For adults the 100- and 300-msec warning intervals reduced the latency of single-step responses and the first saccade of double-step responses, whereas only the 300-msec warning interval was similarly effective with children. In both experiments subjects in all age groups exhibited amplitude transition functions, indicating that the modifiability of saccadic programming is basically similar for adults and children. A comparison of simultaneous programming characteristics of adults and children suggested possible age differences, but the data were not conclusive. The results indicated age differences in the rate of programming and reprogramming saccades but no qualitative age-related differences in these processes.

A comparison of the trace and delay classical conditioning performance of normal children.

Abstract Forty-eight preschool children (CA 48–72 months) of average intelligence and middle-class socioeconomic backgrounds were conditioned to pure tone CSs under trace and delay conditions for 250 single-cue eyelid-conditioning trials. The ISI was 800 msec, with the trace CS having a duration of 50 msec and the CS terminating with the UCS offset. The S ms showed conditioning with both trace and delay CSs but delay S s were at a significantly higher level of performance. Comparisons were made to previous research with retardates, who showed a similar trace deficit, and to college students who did not. The data indicate that the developmental level of an individual is a significant factor in trace conditioning performance.