Schedule-induced Attack Research Articles

The effects on schedule-induced attack of covarying meal size and spacing

Pigeons were exposed to fixed-time food schedules of 30, 120, and 480 sec with two reinforcer magnitudes at each. Attack behavior against a rear-projected conspecific image was assessesd at each interfood/reinforcer magnitude combination. For seven of eight subjects, attack rate was related to interfood interval by an inverted-U or bitonic function. The larger reinforcer magnitude typically induced more attack than the smaller.

Injected testosterone fails to influence schedule-induced attack

Three pigeons attacked a rear-projected conspecific target during exposure to a response-independent Fixed-Time 120 sec (FT 120 sec) and food delivery schedule. After baseline attack rates were established, subjects experienced two conditions in which they received injections (IM) of testosterone (10 mg and 20 mg; 100 mg/ml, in suspension) twenty minutes before session start. No concomitant change in attack rate or temporal location of attack was observed. Findings support observations suggesting that social context is an important determiner of the effects of testosterone on aggressive behavior.

Control of the temporal location of schedule-induced attack in pigeons

Pigeons were exposed to complex fixed-ratio schedules to assess whether the temporal location of schedule-induced attack was controlled by the discriminative properties of food or by the aversive aftereffects of food withdrawal. When exposed to a multiple fixed-ratio 25 fixed-ratio N schedule in which either fixed-ratio component occurred with equal probability according to a quasi-random sequence and in which the value of N ranged from 115 to 150 across subjects, all pigeons exhibited post-food attack against a rear-projected conspecific target predominantly at the signalled onset of the higher-valued ratio component. Exposure of subjects to a mixed fixed-ratio 25 chained fixed-ratio 25 fixed-ratio N-25 schedule, however, resulted in a shift of attack to the signalled onset of the fixed-ratio N-25 component rather than following food. A chained fixed-ratio 25 fixed-ratio N-25 schedule induced attack predominantly after food delivery rather than at the onset of the fixed-ratio N-25 component. These findings show that the temporal locus of schedule-induced attack is primarily controlled by a stimulus, whether food delivery or key color change, that reliably precedes a relatively long period of reinforcer unavailability.

Effects of limited-target availability on schedule-induced attack

Pigeons exposed to a 180-sec fixed-time food schedule could attack a rear-projected conspecific target that was available either (a) continuously throughout the interfood interval, (b) randomly during one 30-sec portion of each interfood interval, or (c) during the final 90 sec of each interval. During continuous-target availability, attack was maximal shortly after food ingestion and progressively decreased thereafter. During random-target availability, five of seven pigeons attacked less per target-access period the later that period occurred within the interfood interval, whereas two subjects exhibited relatively high local attack rates even when access periods occurred within the final third of the interval. When the target was available only during the second half of the interfood interval, attack occurred as soon as the target was presented and progressively decreased throughout the remainder of the target-access period. In general, these results show that schedule-induced attack can be increased by limiting the availability of that target and also indicate that such attack can reliably occur at times other than shortly after food delivery.

Attack induced by second-order schedules of reinforcement

Food-deprived pigeons were exposed to tandem, chain, and brief-stimulus second-order schedules in which the completion of three 80-sec fixed-interval components was followed by food delivery. Two birds attacked a nearby stuffed pigeon shortly after the presentation of either food-paired or food-nonpaired visual stimuli, as well as following food. The third subject exhibited predominantly postfood attack. These results suggest that the locus of schedule-induced attack can be controlled by a stimulus event, whether food delivery or key-color change, that reliably precedes a relatively long period of food unavailability.

A comparison of schedule-induced attack in White King and White Carneaux pigeons

The following conditions were presented to 12 White King and 12 White Carneaux pigeons: a fixed-time (FT) 90-sec food schedule, no food, and a return to the FT schedule. Schedule-induced attack against a pictorial target was sustained throughout the experiment for 10 White Kings and 4 White Carneaux. These results are consistent with other studies using either White Kings or White Carneaux with a pictorial target and strongly support the conclusion that White King is the more aggressive strain.

Schedule-induced attack on a pictorial target in feral pigeons (Columba livia)

Two of three feral pigeons exhibited schedule-induced attack on a colored photograph of a conspecific during exposure to a fixed-time food schedule. The rate and pattern of attack were comparable to that observed with domesticated pigeons. Schedule-induced attack against a conspecific target image is not confined to domesticated birds.

Visual target control of schedule-induced aggression in white king pigeons (columba livia)

Visual target control of schedule-induced attack was studied in domesticated pigeons by exposing them to successive and simultaneous target preference procedures involving a fixed-time food schedule and projected target images. Pigeons preferred attacking an image of a conspecific head over a headless bird regardless of the height of the latter. Images of an intact bird and of a head alone were equally effective in controlling attack and more effective than the headless bird. Neither the eye nor four. other head-related features exclusively controlled attack. The combined results suggest that the head of an intact conspecific target selectively controls schedule-induced attack and that the effectiveness of the head in directing attack is inversely related to its physical integrity as a unit without regard to specific features. These results are consistent with reports that the head and head-related features of an intruder control reproductive aggression in birds.

Schedule-induced attack as a function of length of exposure to a fixed-time 90-sec schedule

Twenty-four White King pigeons were exposed to a fixed-time (FT) 90-sec schedule of food presentation. For half of the subjects, a pictorial target was presented during the second session with the FT 90-sec schedule and throughout the remainder of the experiment. For the remaining subjects, the target was not made available until Session 26 with the FT 90-sec schedule. During early target availability, more subjects attacked in the late introduction condition. After extended exposure to the reinforcement schedule, however, similar numbers of subjects attacked in the two groups, eight in the early and nine in the late introduction group. The data suggest that when subjects are exposed only to a reinforcement schedule of moderate density, extended exposure with or without the target increases the probability that they will subquently attack the target.

Schedule-induced aggression in humans and animals: A comparative parametric review

Studies of animal and human aggression induced by schedules of reinforcement are reviewed. Parameters reviewed include: schedules, characteristics of induced aggression, subject variables, target variables, and the control or modification of schedule-induced aggression. With the exception of temporal locus of schedule-induced attack, the parameters identified with animal subjects are remarkably similar to those identified with human subjects.

Variables affecting establishment of schedule-induced attack on pictorial targets in White King pigeons.

White King pigeons exposed to food schedules before introduction of a colored photograph of a pigeon showed sustained schedule-induced attack on that image; additional birds given an early introduction to both the photograph and the schedule subsequently attacked the image at lower rates. Other pigeons attacked a second photograph of a pigeon regardless of whether it was introduced early or late. The late-introduction procedure was also effective in establishing attack on a projected image of a conspecific. The combined results showed that 14 of 17 White King pigeons given a late introduction to a pictorial target exhibited sustained attack against it and that a pigeon's initial reaction to a photograph of a conspecific when introduced early was a good predictor of subsequent schedule-induced attack on it.

RELATION BETWEEN LEVEL OF FOOD DEPRIVATION AND RATE OF SCHEDULE‐INDUCED ATTACK1

The relation between food deprivation and schedule-induced attack was investigated in four White Carneaux pigeons. Attack toward a mirror target was induced by a schedule of reinforcement in which 3-sec food presentations occurred at alternate intervals of 15 and 120 sec (multiple fixed-time 15-sec fixed-time 120-sec schedule). A continuous tone was presented during the 15-sec periods; it was absent during the 120-sec periods. Each pigeon was tested at 65, 80, and 95% of its free-feeding weight in ascending, descending, and ascending orders, respectively. Two relations were apparent; an inverse relation between body weight and rate of attack, and a tendency for rate of attack to increase during the experiment. Reduction or elimination of attack when the mirror was covered with brown paper for some sessions indicated that the results were due neither to changes in activity that might covary with weight nor to habituation to the experimental situation.

PICTORIAL TARGET CONTROL OF SCHEDULE‐INDUCED ATTACK IN WHITE CARNEAUX PIGEONS1

Three pigeons with a history of attacking a mirror target, and two of six pigeons with no prior exposure to targets, attacked a colored photograph of a conspecific during exposure to intermittent schedules of reinforcement for key pecking. Rate of attack on the photograph decreased when the reinforcement schedule was removed. The topography, temporal pattern, and locus of attack on the picture were comparable to schedule-induced attack on live, stuffed, and mirror targets. When silhouette, outline, and plain paper targets were used, schedule-induced attack was more sensitive to a change in target characteristics with a concurrent target-preference procedure than with an analogous successive-testing procedure. The combined results of the two testing procedures indicated that an "upright" white-on-black silhouette of a pigeon with or without an eye was more effective in controlling attack than was a comparable "inverted" silhouette, an outline of a pigeon, or a piece of colored paper.