Harold L. Hawkins

Parallel processing in complex visual discrimination

In a “same-different” reaction time (RT) task pairs of stimuli varying along one or more dimensions are presented and S is required to indicate, as rapidly as possible, whether the stimuli are physically identical or different. This task was employed in three experiments investigating the processes by which multidimensional stimuli are discriminated. The results indicated that stimulus dimensions are compared in parallel; that the time required to interrogate a dimension varies randomly across trials and is dependent upon the time required to interrogate other dimensions present in test stimuli, and that comparisons terminate upon the detection of information sufficient for a correct response.

Effects of target luminance and cue validity on the latency of visual detection

Hughes (1984) has reported that the magnitude of the cue-validity effect in luminance detection is unaffected by target luminance. In three experiments, we explored the possible basis of this counterintuitive finding. The experiments focused on the design of the Hughes study, in which target luminance was treated as a between-blocks variable. Our results reveal that when target luminance is varied randomly within trial blocks, the cue-validity effect grows with declining target luminance. The difference between our findings and those of Hughes is interpreted in terms of cue-utilization strategies, which may adapt to target luminance when luminance remains invariant within trial blocks. Several alternative conceptions of the nature and locus of the cuevalidity effect in luminance detection are considered in light of these results.

Obedience as a function of experimenter competence

The purpose of this study was to investigate obedience to an E’s commands as a function of E competency. Based upon Orne’s (1962, 1969) discussion of the demand characteristics inherent in the typical aggression study, it was hypothesized that E incompetence would decrease S obedience. Competence was manipulated by: (1) presenting some Ss with a nervous and inexperienced E, and (2)“accidentally” killing the victim (a rat) midway through the experiment. Thirty-two undergraduate female Ss participated in the experiment—supposedly a study on the physiological effects of stress. Obedi6nce was operationalized as the difference, in simple reaction time, between trials on which Ss were told that their response might result in shock to the rat and trials on which they were told that their response might save the rat from shock. Significant differences in obedience were obtained between competent and incompetent E conditions, and a significant “kill” effect was found in the competent E conditidn. The results of this study suggested that the extreme acts of obedience observed in the laboratory (e.g., Milgram, 1963) occur only when E is perceived as competent. This finding imposes limits on the generalizability of laboratory studies of obedience.

The relative frequency effect and S-R compatibility

The influence of relative stimulus frequency on choice reaction time (RT) was studied in a task containing many: 1 S-R mappings and 2 levels of S-R compatibility. Choice RT increased with declining stimulus frequency, and the magnitude of this decline remained invariant across levels of compatibility. Variations in response relative frequency exerted no influence on performance under either level of compatibility. These results are consistent with a perceptual interpretation of the relative frequency effect.

The effects of visual contact and aggressor identification on interpersonal aggression

Groups of four Ss were ordered by the E to respond in a simple reaction time (RT) task in a way which (allegedly) would lead to the delivery of painful shock to a human “victim.” It was found that compliance with these orders declined under conditions where the victim was given the specific identity of the potential harmer. However, compliance was not directly influenced by whether or not the victim and potential harmer were in visual contact.

The inhibitory effects of an observer on instrumental aggression

The purpose of this study was to investigate the effect of explicit threat of retaliation and guilt on instrumental aggression. Thirty undergraduate females were assigned randomly to one of the three following conditions: (l) no retaliation, (2) retaliation, or (3) no-retaliation/ observer present. Each S supposedly delivered electric shock to a victim (actually a confederate) for 20 trials. Post hoc comparisons of all means disclosed significantly less aggression in Conditions 2 and 3 than in Condition 1. The inhibitory effect of retaliation was consistent with Penner & Hawkins’s (1971) findings. Rosenberg’s s (1965) concept of evaluation apprehension was used to explain the effect of the observer.

Choice Reaction Time: The Location of Auditory and Visual Similarity.

Each of eight subjects was visually presented four stimulus classes (pairs of letters combining high or low visual and high or low auditory similarity), each class at two locations of similarity (a pair of letters in a given class requiring the same or different responses). Visual-but not auditorysimilarity affected two-choice discrete reaction time, indicating comparisons based solely on visual characteristics and stressing the important role of mode of stimulus presentation in stimulus/response compatibility.

Short-term retention and similarity of word length

The short-term retention of lists containing word quadruples identical in length was measured by the Peterson method. Nine blocks of three lists were presented. The successively presented lists comprising a block contained words identical in length, 3, 6, or 9 letters, while word length varied across blocks. Overall retention declined with increasing word length. Retention also declined with increasing number of successive lists containing words of a common length and increased when immediately preceding lists contained words of different length, indicating that proactive interference varies as a function of the similarity in length of recently stored items