An explanation of conservatism in the bookbag-and-pokerchips situation

An experiment is described in which subjective probability revisions were obtained in a standard probability estimation task, the ‘bookbag-and-pokerchips’situation. Three aspects of probability revision were examined: conservatism, sequential effects, and coherence. Under two experimental conditions, the conservatism effect obtained was closely related to subjects' use of a simple strategy. A recency effect was also obtained. Coherence of the probability estimates was excellent. Conditions under which the observed strategy leads to conservatism are explored and previously published results are reconsidered in the light of this strategy. Conservatism in the bookbag- and-pokerchips situation is explained as an artefact of subjects' strategies     

Magnitude production and magnitude estimation of taste intensity

Magnitude productions of sodium chloride (salty), quinine hydrochloride (bitter), and sucrose (sweet) yielded steeper psychophysical functions than those obtained with magnitude estimation. Hydrochloric acid (sour) produced the opposite effect. The results are discussed with respect to previous findings in taste intensity scaling and to general psychophysical considerations.     

Inverse relation between choice and local response rate with a schedule of response-produced blackouts

Pigeons were exposed to a two-key concurrent chains schedule in which identical frequencies and distributions of food presentations generated different response rates in the terminal links. An inverse relation between local rate of response in the terminal links and relative frequency of response in the initial links was observed. The high response rate was produced in one terminal link by a second-order schedule in which responding produced brief blackouts of the response key. Responding under the same schedule in the other terminal link did not produce blackouts. Under initial training and after spatial reversal of the terminal-link schedules, two of three pigeons had lower relative frequencies of response in the initial member of the chain with the higher terminal link response rate. The third pigeon showed no change in preference at reversal.     

Two temporal parameters of food postponement

Rats were trained to press a lever under schedules of food postponement. In the absence of lever presses, food was delivered periodically (food-food interval). Responses initiated a second interval (response-food interval) that was reset by each additional response. Performance was first studied at different response-food intervals with the food-food interval fixed at 30 or 60 sec, or 10 min. Response-food intervals were examined in ascending order and then recovery was studied at shorter intervals. Finally, the food-food interval was manipulated with response-food interval fixed at 30 sec. At food-food intervals of 30 and 60 sec, responding first increased and then decreased as the response-food interval increased. At the 10-min food-food interval, responding decreased with increasing response-food interval. In general, very low rates of responding occurred when the response-food interval was 60 sec or more and when it equalled or exceeded the food-food interval. However, responding was maintained in one animal when the food-food interval was decreased from 120 to 15 sec with the response-food interval at 30 sec. Results, in terms of several dependent variables, are compared with data on shock avoidance. Effects of response-independent and response-produced food and shock are discussed.     

Preference for locus of punishment in a response sequence

Food-deprived pigeons pecked a key under a schedule in which grain was made available after the seventieth peck. In each sequence of 70 responses, either the first, middle, or final response was followed by electric shock. Before the first response of each sequence, each response on a second key changed the color of the food key and the schedule of shock that was correlated with the food key color. Each pigeon preferred a schedule of shock, in that each of the three shock schedules did not occur equally often. The preferred shock schedule and the strength of the preference varied among the pigeons. The overall rate of responding by a pigeon under a given shock schedule was directly related to the pigeon's relative preference for that schedule, except when shock after the first response in the sequence was the most preferred schedule.     

A method for the precise switching of speech

A simple procedure by which a speech signal may be switched on or off (or from one ear to the other) at a precise instant of time is described. The speech sample is first recorded on a magnetic tape loop. A reference pulse is then recorded preceding the speech signal. This reference pulse triggers an adjustable time delay which in tum operates an electronic switch at an appropriate time.     

Out of the frying pan into the goalbox

Using heat as a negative reinforcer was shown to be highly efficient in producing a discriminative response in Long-Evans rats. Heat failed to generate the emotional responses usually associated with shock as an aversive stimulus. In a separate study, using the heat-training procedure, age differences in the learning facility of Swiss/ICR (Ha) mice were detected.     

A comparison of leverpress and head-poke discriminated Sidman avoidance

A discriminated Sidman avoidance procedure used by Forgione (1970) was replicated using a head-poke response instead of a leverpress as the avoidance operant. The resultant data were described in terms of the five dependent measures reported by Forgione. Head-poke avoidance was found to be more efficient than its leverpress counterpart and compared very favorably with the lever-disabling (or shock-timer-on) procedure used by Forgione to break up inefficient leverpress behavior patterns.