Effects of prior agonistic experience on risk assessment and approach behavior evoked by familiar or unfamiliar conspecific odors

Risk assessment and appetitive behaviors in response to familiar and unfamiliar conspecific odors were measured in mice rendered dominant or subordinate by a series of resident-intruder encounters. Subordinate mice showed elevated levels of risk assessment in response to the odors of both familiar dominant and unfamiliar males. These behaviors were almost totally absent among dominant males exposed to familiar subordinate or unfamiliar male odors. Subordinate mice showed a marginally significant elevation in latencies to approach familiar, but not unfamiliar, dominant odors. Dominant and subordinate mice spent comparable amounts of time in the cage area containing familiar antagonist odors, however, and the durations of subordinates were mildly elevated, rather than decreased, when unfamiliar conspecific odors were present. There were no group differences in any of the appetitive behaviors. These findings suggest that apparent preferences for conspecific odors may arise from quantitatively and/or qualitatively differing emotional states. The inclusion of risk assessment measures is suggested to be a useful adjunct for studies of olfactory preference/rejection. © 1994 Wiley-Liss, Inc.     

Novel odors evoke risk assessment and suppress appetitive behaviors in mice

The effects of four novel odors on risk assessment by mice (i. e., flat back approach, stretched attention, immobility) and the suppression of appetitive behaviors were examined in two experiments. When novel odors were presented in a straight runway, subjects spent significantly less time in the odor compartment, relative to controls, when it contained sheep wool, chocolate, or citronella (but not cat fur) odors. Risk assessment behaviors occurred at similar levels among all groups and appetitive behaviors were not suppressed by the novel odors. When odorants were scattered over one half of the subjects' home cage floor in Experiment 2, all novel odors increased the duration of at least on e risk assessment measure and/or suppressed appetitive behaviors (i. e., eating, grooming, rearing). The results clearly reveal that a reasonably wide range of novel odors evoke at least some level of risk assessment which presumably reflects increased fearfulness. The odors of sheep wool and cat fur induced a wider range of such responses than did chocolate or cinnamon suggesting that mammalian odors may be particularly effective stimuli. If so, however, it is clear that predator odors are not uniquely effective in this regard. Experiment 1 also underscores the importance of the testing environment in assessing the behavioral effects of novel odors in mice. © 1993 Wiley-Liss, Inc.     

Olfaction,Emotion and Associative Learning: Effects on Motivated Behavior

Two experiments were conducted to investigate emotional associative learning to odors and subsequent behavioral effects. In Experiment 1, participants experienced a frustration mood induction in the presence of an unfamiliar ambient odor and later worked on puzzle tests in a room scented with either the same-odor, a different-odor, or no-odor. Participants in the same-odor condition spent significantly less time working on the tests than participants in the other conditions; however, test accuracy did not vary. To clarify the findings, Experiment 2 included a test-only control and an emotionally neutral same-odor conditions. Results were compatible with the conclusion that decreased time spent by participants in the negative-same-odor condition was due to emotions elicited by associative learning to the ambient odor, although alternative interpretations remain possible. These data extend our previous results with children and suggest that odors readily become associated to emotions and can thereby influence behavior.     

Effects of novel odors on intermale attack behavior in mice

Offensive, defensive, and nonagonistic social behaviors of resident male mice toward unfamiliar intruders were examined during exposure to the novel odors of chocolate or sheep's wool. Both novel odors reduced lateral attacks and boxing when compared to familiar sawdust odor. Chocolate, but not sheep's wool, also reliably increased flight behavior by residents. Neither social behaviors nor self-grooming were affected by these odors. The novel odors had no effect upon, or actually decreased, the defensive responses of intruders towards residents. The equivalent effectiveness of both predator and nonpredator odors in elevating risk assessment and suppressing attack during firsttime exposure, and the decreased potency of cat odors following repeated exposure, suggests that novelty contributes to the enhanced defensiveness seen among subjects during initial exposure to predator odors. © 1995 Wiley-Liss, Inc.     

Money does not stink: Using unpleasant odors as stimulus material changes risky decision making

Odors are strong elicitors of affect, and they play an important role in guiding human behavior, such as avoiding fire or spoiled food. However, little is known about how risky decision making changes when stimuli are olfactory. We investigated this question in an experimental study of risky decision making with unpleasant odors and monetary losses in a fully incentivized task with real outcomes. Odor and monetary decisions were matched so that monetary losses corresponded to the amount of money participants were willing to pay to avoid smelling an odor. Hierarchical Bayesian analyses using prospect theory show that participants were less sensitive to probabilities when gambling with odors than when gambling with money. These results highlight the importance of taking the sensory modality into account when studying risky decision making.     

Effects of early exposure to intermale aggression on the aggressiveness of adult male mice varying in their genetic disposition for aggressive behavior

This study examined whether adult male aggression is influenced by either visual or olfactory exposure in early postnatal life to brief episodes of aggression. Another focus of interest was the interplay between a genetic disposition for aggressive behavior and early exposure experiences. The subjects used in the study were male mice of the 49th generation of selection for high (Turku Aggressive, TA) and low (Turku Non-Aggressive, TNA) levels of aggressiveness. Moderately aggressive males of the parental strain (Normal, N) were also used. Subjects of each strain were exposed from 21 to 32 days of age to fighting males either behind a wire mesh or glass screen. Control subjects were isolated during the entire experimental period. At 90–100 days of age, each subjects was tested three times for its aggressiveness. Exposure to fighting males behind a wire mesh screen enhanced later aggressiveness of juvenile male mice. Juveniles exposed solely to visual cues were comparable to isolates, both groups showing less adult aggression. Early experience and the genetic disposition for aggression were correlated; TA males showing the greatest increase in aggressive behavior. The role of early olfactory learning is discussed. © 1993 Wiley-Liss, Inc.     

Attack by female mice on “Strangers”

In this study the aggressive responses directed by small groups of female mice towards virgin, pregnant, and lactating female strangers, which were individually introduced into their cages, were compared. The results obtained show that, except when lactating, pregnant females are neither attacked much more often nor any more severely than virgin mice. It is suggested that only the state of lactation favors the production of stimuli (olfactory) which release attack by female mice.     

Smelling matter

While the objects of olfaction are intuitively individuated by reference to the ordinary objects from which they arise, this intuition does not accurately capture the complex nature of smells. Smells are neither ordinary three-dimensional objects, nor Platonic vapors, nor odors. Rather, smells are the molecular structures of chemical compounds within odor plumes. Molecular Structure Theory is offered as an account of smells, which can explain the nature of the external object of olfactory perception, what we experience as olfactory objects, and what determines the olfactory quality of smells by which we can demarcate the spatiotemporal boundaries of smells.