Discrete dynamic choice: An extension of the choice models of thurstone and luce

The present paper deals with the extension of two well-known static discrete choice theories to the dynamic situation in which individuals make choices at several points in (continuous) time. A dynamic version of Luce's Axiom, “independence from irrelevant alternatives”, is proposed and some of its implications are derived. In the static case Yellott (J. Math. Psych. 1977, 15, 109–146) and others have demonstrated that an independent random utility model generated from the extreme value distribution exp(?e^?ax?b) becomes equivalent to Luce's Axiom. Yellott also introduced an axiom called “invariance under uniform expansions of the choice set”, and he proved that within the class of random utility models with independent identically distributed utilities (apart from a location shift) this axiom is equivalent to Luce's Axiom. These results are extended to the dynamic situation and it is shown that if the utility processes are expressed by so-called extremal processes the corresponding choice model is Markovian. A nonstationary generalization is proposed which is a substantial interest in applications where the parameters of the choice process are influenced by previous choice experience or by time-varying exogenous variables. In particular, it is demonstrated that the nonstationary model is Markovian if and only if the joint choice probabilities at two points in time have a particular form. Thus, the paper provides a rationale for applying a specific class of Markov models as the point of departure when modelling mobility processes that involve individual discrete decisions over time.     

The effects of distributed training on retention of operant conditioning in human infants

Long-term retention of operant footkicking acquired in the mobile conjugate reinforcement paradigm was assessed as a function of the distribution of training time. In the first study, 3-month-old infants were trained for either one 18-min session or for two 9-min or three 6-min sessions separated by 24-hr intervals. All infants exhibited retention during a test administered immediately after training, but only those trained in a single session continued to perform the conditioned response during cued-recall tests 7 or 14 days later. Infants trained in three sessions showed no evidence of remembering the contingency even after a week. A warm-up decrement, seen in the day-to-day performance of infants in the distributed conditions, was eliminated in the second study by the interpolation of a nonreinforcement period at the outset of daily sessions. This procedure also enhanced long-term retention such that infants trained in three 6-min session now remembered the contingency for 14 days and did not differ from infants who had received a single 18-min session. Whether distributed training facilitates or impairs long-term retention appears to depend on the opportunity for infants to acquire a sufficient number (or kind) of effective retrieval cues during original learning.     

Spatial representations of young children: the role of self- versus adult-directed movement and viewing

The influence of the control of movement and viewing while exploring a novel large-scale environment was assessed. Forty kindergarteners and forty second grade children served in four activity conditions that represented the factorial combination of movement (self vs adult directed) and viewing (self vs adult directed). A significant grade level X movement X viewing interaction revealed that when kindergarteners directed their own movement, estimates of interlocation distances were equivalent whether viewing was self or adult directed. If movement was directed by an adult, kindergarteners estimated interlocation distances more accurately if the adult also directed their viewing than if the children directed their own viewing. Second grade children performed comparably across all four experimental conditions.     

Variations of the Bender-Gestalt Test: implications for training and practice

Although the Bender-Gestalt Visual Motor Test has been a popular and influential clinical assessment instrument for the last half century, authoritative opinion and a substantial research literature are often inconsistent or contradictory. This paper documents variations in designs, administration procedures, forms, and applications to particular populations. A careful review of scoring systems indicates the current status of objective approaches as contrasted with interpretation that is global, intuitive, and subjective. Some implications of these variations and interpretive procedures for training and assessment practice are discussed. The major conclusions of the review are summarized in seven points.     

Diagnostic validity of the MMPI and two short forms

The ability of the Faschingbauer Abbreviated MMPI (FAM) and the MMPI-168 to substitute for the full Minnesota Multiphasic Personality Inventory (MMPI) in broad psychiatric diagnosis was examined in a sample of 514 psychiatric inpatients. Each sex was randomly divided and multiple discriminant functions derived using long form scales as predictors. The discriminant functions were cross-validated on the other same-sex group using long and short form scales as predictors. All three forms achieved a 46% "hit" rate overall. No significant differences among the three forms were found.     

A review of projective test findings with older adults

The projective test literature on aging is reviewed. It was concluded that, while much critical research remains to be done and many of the studies are flawed, projective testing has contributed a great deal to the understanding of the aging process and has yielded a core of consistent findings. Suggestions for future research which would help resolve some current ambiguities were made.     

Response rate, latency, and resistance to change

Pigeons were trained on a multiple variable-interval/variable-interval schedule with pacing contingencies that generated high response rates in one component and low response rates in the other. Timeout periods separated the schedule components. During resistance-to-change tests, response-independent food was presented during the timeout periods, and the duration of that food presentation was varied among test sessions. Response rates in the schedule components decreased and latencies to the first response increased as a function of the duration of food presentations during the timeout. Both dependent measures changed about the same amount relative to their own baseline levels. The conclusions are that baseline response rates controlled by pacing contingencies are equally resistant to change, given equal reinforcement densities, and latency is a sensitive measure of resistance to change.     

Tests of a two-stage model of visual matching

Predictions from a model of visual matching were tested in two experiments. The model consists of a wholistic comparison process followed by an element-by-element comparison process. All stimuli are processed by the first stage but only those that permit a decision based on a wholistic comparison produce responses. When discrimination is difficult and a decision cannot be reached by a wholistic comparison, the second stage of processing is initiated. Degree of discriminability and stimulus duration (100 and 1000 msec.) were varied in both experiments. In Exp. 1, the stimulus elements were arranged in a square configuration to facilitate a wholistic comparison. As predicted, the hard-different stimuli took longer to match than the same or easy-different stimuli. The hard-different stimuli presented for 1000 msec. took longer to match than those presented for 100 msec. There was no difference in accuracy between responses to hard-different pairs at the two durations. In Exp. 2, the stimulus elements were arranged in a horizontal row and placed one above the other to facilitate element-by-element comparison. As predicted, these stimuli produced slower and more accurate responses for same and hard-different stimulus pairs only when they were exposed for 1000 msec. Responses to easy-different stimulus pairs were made quickly and accurately.