Two pigeons were exposed to a multiple schedule of reinforcement: in the presence of one discriminative stimulus, key pecks produced grain according to a fixed-ratio schedule; in the presence of a second discriminative stimulus, key pecks produced grain according to a variable-ratio schedule. The key-peck requiremiients in the two components were increased in successive stages from 50 to 125 responses. Live target pigeons were restrained at the rear of the chamber. Attacks against the targets were automatically recorded, and a variety of measures of attack behavior were taken. Attacks, when they occurred, always followed grain presentation. All measures revealed higher levels of attack during the fixed-ratio component at all parameter values. All measures generally increased with increases in fixed-ratio values with both birds, and with increases in variable-ratio values with one bird. With the other bird, only the per cent of reinforcements followed by attack increased with increases in variable-ratio value; all other nmeasures first increased and then decreased. In experiments on schedule-induced aggression, positive reinforcement is usually dependent upon operant responding (e.g., key pecking), and a target is available. Under some schedule parameters, animals will attack either restrained animals of the same species or a variety of inanimate objects. Attack, when it occurs, is primarily a post-reinforcement phenomenon. Schedule-induced aggression has been studied during fixed-ratio schedules

Squirrel monkeys pressed a lever under fixed-interval schedules of food or of electric-shock presentation. Both schedules induced repeated biting on a latex hose. Whether lever pressing was controlled by food or by electric shock, a pattern of decreasing hose biting and increasing lever pressing occurred within fixed-interval cycles. As the fixed-interval duration was increased from 6 to 600 sec, average rates of lever pressing decreased under both schedules. Average rates of hose biting first increased with increasing parameter value, reaching a maximum at values that varied from 60 to 337 sec in different monkeys, and then declined at higher values. d-Amphetamine at appropriate doses increased overall rates of lever pressing maintained by food or by shock, but either did not affect or decreased overall rates of hose biting. When no timeout period occurred between fixed-interval cycles, the monkeys bit most frequently immediately after food or electric shock was presented. When there was a timeout period, hose biting began shortly after the start of the fixed-interval cycles, with little or no hose biting immediately after food or electric shock was presented. Most hose biting appeared to be schedule-induced rather than food- or shock-induced.

Behavioral toxicity of toluene has been measured in mice. Because of its small size the mouse can be confined in a 25 1. hermetically sealed chamber for several hours. Toluene was introduced through a port and vaporized by a hotplate. Samples of chamber air for analysis were taken through another port. A smaller mesh cage held the mouse within the larger chamber. Schedule-controlled responding was developed by arranging that a response, breaking a beam of light, was followed by milk under an FI 60-sec schedule. Responding was much more rapid in the presence of stimuli correlated with the FI schedule than when the schedule was not operating. Standard sessions consisted of alternating series of 8 consecutive FI 6dsec and interseries 30-min time-outs.Following introduction of liquid toluene, the concentration in the chamber reached its asymptote within 60 sec. Toluene disappeared from the atmosphere of the unopened empty chamber at the rate of 0.2%/hr. When the mouse cage was in the chamber the disappearance was 1.5%/hr and when a mouse was also present it was 3.5%/hr. Effects of toluene on the behavior of the mouse reached a plateau within 30 min of continued exposure to a fixed concentration. Concentration-effect curves were constructed from the number of responses in a series of FPs following 30-min exposure to a concentration of toluene as compared to the control number on that day. In some experiments mice were exposed to a single concentration of toluene: in other experiments, more toluene was added after a series of FI so the mice were exposed to incrementally increasing concentrations. The two procedures generated similar concentration-effect curves. Toluene increased the rate of responding in most mice at levels of about 700 ppm. Higher concentrations progressively reduced responding. The ED 50 (the concentration reducing responding by 50%) averaged 1657 ppm in 10 mice.

Pigeons were exposed to seven types of two-component schedules, each component a 2-min fixed-interval schedule. Food presentation occurred at the completion of the second component under all conditions. The seven types of schedules were: (1) a chained schedule in which completion of the first component produced the discriminative stimulus associated with the second component; (2) a chained schedule to which was added the brief presentation of a food-paired stimulus at the completion of the first component; (3) a chained schedule to which was added the brief presentation of a stimulus not paired with food at the completion of the first component; (4) a multiple schedule in which food presentation occurred at the completion of both components; (5) a tandem schedule in which completion of the first component initiated the second component, with no changes in exteroceptive stimuli; (6) a food-paired brief-stimulus schedule in which the brief presentation of a food-paired stimulus was made at the completion of the first component and no other changes in stimuli occurred; and (7) a brief-stimulus schedule in which the brief presentation of a stimulus not paired with food was made at the completion of the first component and no other changes in stimuli occurred. Positively accelerated patterns of responding developed in the first component under three conditions: (1) the chained schedule with the added food-paired brief stimulus; (2) the multiple schedule; and (3) the food-paired brief-stimulus schedule. Response rates were low in the first component, with few instances of positively accelerated patterns, under two conditions: (1) the chained schedule; and (2) the chained schedule with the added nonpaired brief stimulus. The results suggest that a briefly presented food-paired stimulus may function as a more effective conditioned reinforcer than does the presentation of a discriminative stimulus.