The visual perception of rigid motion from constant flow fields

Four experiments investigated observers’ judgments of rigidity for different types of optical motion. The depicted structural deformations were of two types: (1) those with nonparallel image trajectories that are detectable from the first-order spatiotemporal relations between pairs of views; and (2) those with parallel image trajectories that can only be detected from higher order relations among three or more views. Patterns were composed of smooth flow fields in Experiments 1 and 3, and of wire frame figures in Experiments 2 and 4. For both types of display, the nonrigidity detectable from the first-order spatiotemporal structure of the motion sequence was much more salient than the deformation detectable only from the higher order spatiotemporal structure. These results indicate that observers’ judgments of rigidity are based primarily on a two-view analysis, but that some useful information can be obtained under appropriate circumstances from higher order spatiotemporal relations among three or more views.     

Predictability,controllability, and inoculation against learned helplessness

Nondepressed human subjects were divided into seven groups. On a series of discrimination problems, a helplessness group received insoluble problems, a solvable group received contingent feedback, and a no treatment control group received no feedback. For two other groups insoluble problems were preceded by success feedback on a different task presented according to a fixed ratio (FR) or variable ratio (VR) schedule of reinforcement. Two control groups received either FR or VR schedules of success but were not examined on the discrimination problems. All groups were tested for escape/avoidance performance on a human shuttle box. Both FR and VR schedules produced an inoculation against learned helplessness; escape performance by the helplessness group was significantly worse than that of FR and VR inoculation groups. These latter groups performed similar to the solvable and three control groups. Significantly worse than that of FR and VR inoculation groups. These latter groups performed similar to the solvable and three control groups. Significantly fewer subjects in the VR inoculation group exhibited avoidance responses than their counterparts in the FR inoculation group. despite similar escape performance. The findings indicate that learned helplessness can be prevented in humans and suggest different sources of interference produced by unpredictable and uncontrollable events.     

Relative costs and statistical power in the extreme groups approach

The relationship between variables in applied and experimental research is often investigated by the use of extreme (i.e., upper and lower) groups. Recent analytical work has provided an extreme groups procedure that is more powerful than the standard correlational approach for all values of the correlation and extreme group size. The present article provides procedures to optimize power by determining the relative number of subjects to use in each of two stages of data collection given a fixed testing budget.The opinions or assertions contained herein are those of the writers and are not to be construed as official or reflecting the views of the Navy Department.Edward F. Alf, Jr. is also affiliated with the Department of Psychology, San Diego State University.     

Do the mentally retarded have poor memory?

The hypothesis that mentally retarded persons have a short-term memory deficit whixh is due to inadequate rehearsal strategies is reexamined. A reevaluation of results of a number of experiments suggests that normal and retarded persons differ on short-term memory tasks, and the superiority of normals is present from the time of initial stimulus exposure. While some evidence for slope differences in retention curves is found in a few tasks, it is not strong support for memory differences. The hypothesis that “memory” differences are due to differential encoding as a result of more adequate rehearsal by the normal subjects is unacceptable. If this were the case, some differences in slope of retention curves could be expected unless rehearsal beyond the encoding stage was totally precluded. The review points to a need for an empirical reevaluation of the issue with a full recognition that deficits in particular processes may characterize some retarded persons and not others.     

Accessibility of the voicing distinction for learning phonological rules

In three experiments a series of nonsense syllables ending in consonants was presented to adult subjects who had to discover or learn a rule classifying the syllables into two groups. The rule was based either on the voicing of the final consonants or on an arbitrary division of them. Subjects performed better with the voicing than with the arbitrary rule only when there was a straightforward relationship between the voicing rule and the plural formation rule in English or, more generally, when voicing assimilation with an added consonant was involved and attention was focused on the sound and articulation of the syllables. We conclude that the voicing distinction is not ordinarily accessible and that individuals easily learn and use phonological rules involving voicing assimilation because of articulatory constraints on the production of consonant clusters.     

Contrast and undermatching as a function of reinforcer duration and quality during multiple schedules

Eight pigeons pecked keys under multiple variable-interval two-minute variable-interval two-minute schedules. In Experiment 1, the reinforcers were 2, 4, or 8 seconds access to a food magazine. In Experiments 2 and 3, the reinforcers were grains that had been determined to be most-, moderately-, or non-preferred. Both positive and negative behavioral contrast occurred when the reinforcers in one component were held constant and the duration or type of reinforcer obtained in the other component varied. Undermatching occurred when the relative rate of responding during a component was plotted as a function of the relative duration of the reinforcers in that component.     

Syllable-internal structure and the sonority hierarchy: Differential evidence from lexical decision,naming, and reading

Treiman (1983) and others have argued that spoken syllables are best characterized not as linear strings of phonemes, but as hierarchically organized units consisting of an onset (initial consonant or consonant cluster) and a rime (the vowel and any following consonants) and that the rime is further divided into a peak or nucleus (the vowel) and a coda (the final consonants). It has also been argued that the sonority (or vowel-likeness) of the consonant closest to the peak, which is a function of its phonetic class, may have an effect on the strength of boundaries determined by the hierarchical division of the syllable (e.g., Treiman, 1984). We examined the evidence for syllable-internal structure and for sonority in two experiments that employed visually presented stimuli and lexical decision, naming, and reading tasks. Our results provide support for the breakdown of the rime into a peak and a coda and for an effect of the sonority of the postvocalic consonant on that break. This pattern occurred only in our lexical decision tasks, so the effect is assumed to be postlexical. We did not find an effect of the onset-rime boundary, perhaps because of an unanticipated effect of word frequency. Our results are discussed in terms of phonological coding in short-term memory.     

Aversive procedures: The minnesota experience

Aversive and deprivation procedures for controlling and reducing challenging behaviors have received increasing attention. Many states have adopted guidelines on the use of these procedures treating persons with developmental disabilities. The Minnesota state rule promulgated in October, 1987 requires reviews from both local and state-wide review committees on permitted, but controlled procedures. Data generated from state-wide committees revealed that (a) state operated regional treatment centers (RTCs) employed individual habilitative training programs with controlled procedures more frequently than community-based agencies (b) a higher proportion of RTC submissions were for treatment of self-injury than submissions from community services, and (c) RTCs had a higher usage of mechanical restraints than community facilities with both services settings using manual restraints more frequently than all other controlled procedures combined. Reasons for the above differences in the two service settings were discussed.     

The perception of semantic relations in pictures

Three picture processing experiments are reported that present evidence of an “agent advantage effect,” that is, faster processing of the performer of the action depicted the agent of the action than of the element acted upon (the patient). Experiment 1 demonstrated the effect in a paradigm in which reaction time to manually indicate the location of a target (agent or patient) was faster for agent targets. Experiment 2 demonstrated that the critical time required for subjects to encode the agent was shorter than the time required for encoding patients. Experiment 3 again demonstrated the agent advantage effect in a directed attention paradigm. Together, the results of the experiments indicated that subjects were able to encode agent information faster than patient information. The results also indicated that subjects did not adopt a strategy whereby encoding of patient information was necessarily dependent upon encoding agent information.