Role of gravitational cues in the haptic perception of orientation

The haptic perception of vertical, horizontal, +45°-oblique, and +135°-oblique orientations was studied in adults. The purpose was to establish whether the gravitational cues provided by the scanning arm—hand system were involved in the haptic oblique effect (lower performances in oblique orientations than in vertical—horizontal ones) and more generally in the haptic coding of orientation. The magnitude of these cues was manipulated by changing gravity constraints, and their variability was manipulated by changing the planes in which the task was performed (horizontal, frontal, and sagittal). In Experiment 1, only the horizontal plane was tested, either with the forearm resting on the disk supporting the rod (“supported forearm” condition) or with the forearm unsupported in the air. In the latter case, antigravitational forces were elicited during scanning. The oblique effect was present in the “unsupported” condition and was absent in the “supported” condition. In Experiment 2, the three planes were tested, either in a “natural” or in a “lightened forearm” condition in which the gravitational cues were reduced by lightening the subject’s forearm. The magnitude of the oblique effect was lower in the “lightened” condition than in the “natural” one, and there was no plane effect. In Experiment 3, the subject’s forearm was loaded with either a 500- or a 1,000-g bracelet, or it was not loaded. The oblique effect was the same in the three conditions, and the plane effect (lower performances in the horizontal plane than in the frontal and sagittal ones) was present only when the forearm was loaded. Taken together, these results suggested that gravitational cues may play a role in haptic coding of orientation, although the effects of decreasing or increasing these cues are not symmetrical.     

A method for examining gestural language structure

This experiment tested the hypothesis that syntactic constituents in American Sign Language (ASL) serve as perceptual units. We adapted the strategy first employed by Fodor and Bever in 1965 in a study of the psychological reality of linguistic speech segments. Four deaf subjects were shown ASL sign sequences constructed to contain a single constituent break. The dependent measure was the subjective location of a light flash occurring during the sign sequence. The prediction that the flashes would be attracted to the constituent boundary was supported for two of the subjects, while the other two showed random placement of the flash location on either side of the constituent boundary. The two subjects not performing in the predicted direction were more proficient in English (written) than the two giving the effect. It was suggested that this relatively greater proficiency may have interfered in some way with the ASL syntax to produce the results obtained.     

Proactive inhibition in short-term retention

Summary A model of Estes which describes retroactive inhibition effects was adapted to the process of proactive inhibition in short-term retention. Results obtained by Reutener (1972) with the single-item free recall paradigm could be adequately described with the proposed model.     

The role of haptic versus visual volume cues in the size-weight illusion

Three experiments establish the size-weight illusion as a primarily haptic phenomenon, despite its having been more traditionally considered an example of vision influencing haptic processing. Experiment 1 documents, across a broad range of stimulus weights and volumes, the existence of a purely haptic size-weight illusion, equal in strength to the traditional illusion. Experiment 2 demonstrates that haptic volume cues are both sufficient and necessary-for a full-strength illusion. In contrast, visual volume cues are merely sufficient, and produce a relatively weaker effect. Experiment 3 establishes that congenitally blind subjects experience an effect as powerful as that Of blindfolded sighted observers, thus demonstrating that visual imagery is also unnecessary for a robust size-weight illusion. The results are discussed in terms of their implications for both sensory and cognitive theories of the size-weight illusion. Applications of this work to a human factors design and to sensor-based systems for robotic manipulation are also briefly considered.     

A method for examining the operant self-administration of respirable pharmaceuticals in rodents

Many different drugs of abuse are administered via an inhalation route. However, no pragmatic, infraprimate model has been developed to assess the self-administration of these pharmaceutical agents in the laboratory setting. This paper describes an apparatus designed to assess the self-administration of these pharmaceutical agents in a rodent model.     

The co-ordination of codes in short-term retention

The present experiments explored ways in which information encoded along different dimensions might be co-ordinated to determine memory performance. First, can an acoustic similarity decrement be offset by additional semantic encoding? Experiment I offers evidence for this compensatory interaction of codes. Second, does trade-off occur such that more information held in one code means less in another code? Third, are codes additive? Experiment II offers no support for the notion of a trade-off between encoding systems. However, when two codes were made available in the second study, recall was increased over the level achieved by either code alone.     

Practice effects on the use of visual and haptic cues during grasping

Mapping of arbitrary color cues onto object properties such as mass can influence the control of fingertip forces. One can view the development of that mapping as a motor learning issue, and its development should therefore be influenced by practice schedule. During an acquisition phase, 24 participants lifted color-cued objects that differed in mass. The masses were presented in either blocked or random orders. A test phase consisted of lifts of a midmass object; on some lifts, the object's mass was unexpectedly changed. The change was either accurately color cued or miscued. Only blocked practice led to visually mediated scaling of fingertip forces to object mass. During the test phase, previous blocked practice resulted in reliance on visual cues, and random practice led to a reliance on haptics (sense of touch). Those findings suggest that the integration of arbitrary color cues and haptic information is dependent on practice conditions.     

Relational and absolute cues in auditory discrimination by monkeys

Rhesus monkeys were trained to make auditory frequency, intensity, and duration discriminations. Initial training was carried out with a procedure which allowed the utilization of either relational cues or absolute cues. Later tests with similar auditory parameters allowed only the utilization of relational cues. Performance on these latter tests indicated that relational rather than absolute cues had been utilized when both types were available on the frequency and intensity discrimination tasks. However, absolute rather than relational cues were apparently utilized in making duration discriminations.     

Reactivation-induced interference in a short-term retention paradigm

In Experiment 1 it was demonstrated that interference with a rat's retention of a target spatial cue decreases as the interval between prior conflicting cues and the target increases. Experiment 2 showed that interference can occur even when the interstimulus interval is long, if the memory of a conflicting cue is reactivated just prior to exposing an animal to the target cue. A third experiment suggested that these findings could not be easily interpreted in terms of a stimulus satiation effect. The implications of these findings for a trace decay model of short-term retention were discussed.     

Temporal aspects of retrieval in short-term serial retention

In three experiments, temporal properties of memory retrieval are studied. Latency of positionally probed recall of a single item is measured as a function of its serial position (SP) in a serial list. The requested SP is indicated by a positional probe, presented immediately after the list. For two organizational structures of the list (i.e., grouped vs. ungrouped lists) the experiments study the effects of precueing the probe position briefly before probe presentation, the cue signal indicating the SPs relevant for recall. The problem of confounded effects on latency of requested SP and of probe-signal location is also investigated. A bow-shaped SP-curve is found for ungrouped lists; precueing reduces RT but does not affect the bowed shape. This argues against selective confounding effects of spatial probe position and also suggests that precueing preactivates memory access. Grouping the items into two sublists eliminates precueing effects for items around the group boundary. Furthermore, precueing is detrimental when SPs at opposite ends of the list are precued. This suggests that the available points of memory access can only be utilized one at a time, so that precueing is not beneficial when the item cannot be reached via the preactivated point. Although the notion of single access to memory is in accord with both positional cueing theory and non-associative hierarchical theories (e.g., Estes 1972), various details of the results are in favor of the first type of explanation.