Amnesia,rehearsal, and temporal distinctiveness models of recall

Classical amnesia involves selective memory impairment for temporally distant items in free recall (impaired primacy) together with relative preservation of memory for recency items. This abnormal serial position curve is traditionally taken as evidence for a distinction between different memory processes, with amnesia being associated with selectively impaired long-term memory. However recent accounts of normal serial position curves have emphasized the importance of rehearsal processes in giving rise to primacy effects and have suggested that a single temporal distinctiveness mechanism can account for both primacy and recency effects when rehearsal is considered. Here we explore the pattern of strategic rehearsal in a patient with very severe amnesia. When the patient’s rehearsal pattern is taken into account, a temporal distinctiveness model can account for the serial position curve in both amnesic and control free recall. The results are taken as consistent with temporal distinctiveness models of free recall, and they motivate an emphasis on rehearsal patterns in understanding amnesic deficits in free recall.     

The organization of play fighting in the grasshopper mouse (Onychomys leucogaster): Mixing predatory and sociosexual targets and tactics

The body targets contacted, the type of contact made, and the patterns of defense and counterattack elicited by those attacks are examined in the play fighting of captive male and female pairs of grasshopper mice. The nape was the most frequently contacted body target, irrespective of the type of contact made, be it nosing, allogrooming, biting, or striking with a forepaw. The types of defense varied with both body area contacted and type of attack performed. Based on the topography and pattern of contact, it was concluded that grasshopper mice, as is the case for many other muroid rodents, primarily attack and defend targets otherwise contacted during precopulatory encounters. However, grasshopper mice, which are obligate carnivores, also attack and defend predatory targets, although less frequently than sociosexual targets. Surprisingly, predatory attacks were more likely to be counterattacked with predatory attacks, whereas sociosexual attacks were more likely to be counterattacked with sociosexual attacks. Conspecific aggression involves bites directed at the face, lower flanks, and dorsum. Neither the biting of these areas nor the tactics of attack and defense usually associated with such bites were observed during the juvenile interactions. There were no sex differences in either frequency or patterns of attack and defense in play fighting. The data presented for grasshopper mice shed light on the issue of mixing behavior patterns from multiple functional systems during play. Aggr. Behav. 26:319–334, 2000. © 2000 Wiley‐Liss, Inc.     

Targets and tactics: The analysis of moment-to-moment decision making in animal combat

Even though injury and death are more common consequences of fighting among animals than once believed, they are still relatively infrequent. Modern evolutionary models of animal combat have emphasized that given the threat of retaliation, animals only escalate to more injurious fighting if the benefits outweigh the costs, and then only if threat and bluff fail to achieve the goal. Such models stress the role of communication as to whether animals decide to escalate or not. An alternative view is that failure to produce injury or death arises from the neutralization of one animal's attack by another's defense. That is, attack and defense end in a stalemate that may be misinterpreted by outside observers as an absence of injury producing behavior. As attack typically involves the biting or striking of specific body targets, movements and postures occurring during combat need to be analyzed with respect to their role in gaining or averting such contact. For example, in the combat of muroid rodents the attacker targets the lower dorsum and flanks (low threshold) or face (high threshold), whereas a defender may defensively launch counterstrikes against the attacker's face. Two combat tactics (supine defense and lateral attack) typically present in the fighting of muroid rodents are analyzed in detail to illustrate how targets constrain the movements of combatants. Such a functional analysis of combat assumes that the movements and postures performed are related to their role in the attack and defense of targets. Deviations from such a strict functional interpretation reveal some of the other factors that may constrain the combatants' behavior. For example, body morphology and the aggressiveness of the opponent are shown to be important in deciding the type of combat tactic to use and how it is performed. Finally, movements and postures that are neutral or even counterproductive for attack and defense may be revealed as communicatory. This approach provides a means of analyzing behavior during the "heat of combat" that is typically not dealt with in traditional evolutionary models. Aggr. Behav. 23:107–129, 1997.© 1997 Wiley-Liss, Inc.     

Targets,tactics, and the open mouth face during play fighting in three species of primates

The play fighting of many mammals involves the nonserious use of behavior patterns derived from serious fighting. A major question of theoretical importance has been that of how, given this overlap in patterns of behavior, the animals can distinguish between playful and nonplayful intent. One proposed solution is that animals use play signals to inform each other about the playful intent of their actions. The most widely reported play signal amongst primates is the open mouth play face. The manner in which this so-called signal functions is based on correlational evidence, with most reports simply noting its presence or absence in a given species. This study involved a detailed video-based analysis of the occurrence of open mouths during the play fighting of three species of primates. One captive troop each of ring-tailed lemurs, black-handed spider monkeys, and patas monkeys was used. By examining all open mouths in the context of the species-typical style of play fighting, several conclusions were empirically verified. 1) Most open mouths occur as a functionally necessary precursor for biting. 2) Some open mouths occur as a defensive threat which deters further contact. 3) The residual open mouths which may function as contact promoting play signals, constituted about 20–25% of all open mouths by the lemurs and patas monkeys, but less than 5% for spider monkeys. These species differences appeared to arise from two causes. Firstly, the spider monkeys used another signal, the head shake, in situations where lemurs and patas monkeys used open mouths. Secondly, the style of play fighting greatly influenced the frequency and duration of open mouths. This was most marked in the face-to-face combat style of patas monkeys. These findings show that comparative studies of the occurrence and function of play signals need to take into account species-typical styles of playful combat. Aggr. Behav. 23:41–57, 1997. © 1997 Wiley-Liss, Inc.     

Organization of sex-typical patterns of defense during food protection in the rat: The role of the opponent's sex

Feeding rats defend a food item from an approaching conspecific by turning away, laterally, about 180°. Females and males use a different composition of movements and stepping patterns to perform these defensive dodges. This study was designed to examine the role of the robber's sex on the execution of sex-typical patterns of dodging. All subjects were tested with a partner of each sex. During dodging, females used the female-typical pattern of pivoting around the pelvis, and males used the male-typical midbody pivot, irrespective of the robber's sex. These findings show that the sex-typical patterns of dodging are not determined by the sex of the partner. Females and males however, differed in how they were oriented towards a same sex robber at the end of the dodge. This suggests that while male and female robbers must pose different defensive problems, these differences are dealt with by modifying the sex-typical pattern of dodging rather than by switching to the dodge pattern of the opposite sex. This further suggests that the differences in the composition of the dodge pattern in males and females are not due to extrinsic contingencies, but rather, are due to intrinsic differences in the sex-typical organization of defensive motor patterns. Aggr. Behav. 23:197–214, 1997.© 1997 Wiley-Liss, Inc.     

Play-fighting differs from serious fighting in both target of attack and tactics of fighting in the laboratory rat Rattus norvegicus

Play-fighting is often difficult to differentiate from inhibited or immature serious fighting because both may utilize many of the same behavior patterns. In the rat the two behaviors involve different targets of attack. During play-fighting, snout or oral contact is directed at the opponent's nape of the neck, whereas during serious fighting, male residents mostly direct their bites at the intruder's rump. Although similar to those used in serious fighting, the behavior patterns used during play-fighting are modified to achieve the different targets of attack. Even though the tactics of attack and defense appear more adult-like with increasing age, the playful targets persist well into adulthood.     

Agonistic versus amicable targets of attack and defense: Consequences for the origin,function, and descriptive classification of play-fighting

Play-fighting appears to involve the behavior patterns of attack and defense otherwise seen in serious fighting. The degree of similarity, however, depends on the body targets attacked and defended during these forms of fighting. For many taxa, including diverse mammalian families and some birds, the same targets are attacked and defended during both play-fighting and serious fighting. However, for several species of muroid rodents, the targets of play-fighting are not the same as those of serious fighting. In these cases, the tactics of attack and defense are also different. It is argued that for these muroid species the playful targets have arisen from amicable behavior (e.g., social investigation, greeting, allogrooming) rather than, as appears to be the case in so many other taxa, from agonistic behavior. These data strongly suggest that “play-fighting” has evolved from different precursors in different taxa and thus has multiple origins. Furthermore, these data have an important bearing on the universal applicability of many of the suggested functions of play-fighting and also on how such behavior is to be described and classified.     

Lateral display as a combat tactic in richardson's ground squirrel Spermophilus richardsonii

During fighting, adult ground squirrels frequently face each other laterally, arch the back, and piloerect the tail. In a diurnal species, such distinctive visual cues seem consistent with the suggestion that the lateral display serves a communicatory function. However, a detailed analysis of videotaped sequences of free-living Richardson's ground squirrels from two consecutive mating seasons suggested that the lateral maneuver has a functional role in combat. Because most agonistic encounters involve chasing, the rump is the principal body area bitten. When stationary, however, the opponent's rump is bypassed, and bites are targeted at the shoulders. Defensively, a hip thrust is used to block such attacks to the shoulder by pushing the opponent's head away. Offensively, the lateral maneuver is used to push against the opponent, providing a vantage point from which to lunge at the opponent's shoulders. In addition, the defender can launch counterattacks at the side of the head. The lateral orientation provides the attacker with a means of evading such attacks, by swerving laterally away. In some encounters, both the offensive and defensive variations of the lateral maneuver were used by both opponents, often simultaneously. Therefore, irrespective of the signalling function of the lateral display, much of its occurrence during combat can be explained in terms of its role as a combat tactic. © 1996 Wiley-Liss, Inc.