Bernard B. Schiff

Inducing emotion by unilateral contraction of facial muscles: A new look at hemispheric specialization and the experience of emotion

Subjects who maintained voluntary contractions of the left facial muscles experienced sadness. Right facial contractions resulted in a more positive but difficult to characterize experience. These contractions had similar effects on the affective tone of stories told about an ambiguous picture. These findings indicate that emotions can be aroused by unilateral muscle contractions without intervening cognitions. They provide a new methodology for studying the roles of the cerebral hemispheres in emotional experience. Finally, they support the conclusion that the right hemisphere is involved with negative emotional experiences and indicate that the left hemisphere is involved with experiences that are more positive but not readily characterized.

Inducing Emotion by Unilateral Contraction of Hand Muscles

Following 4 unilateral contractions of hand muscles, subjects told stories about pictures from the T.A.T. A propositional analysis of the stories showed that the emotional tone of stories told following left hand contractions were more negative than those told after right hand contractions. These results are comparable to those reported following unilateral facial contractions and are consistent with the arousal of the emotional properties of the hemisphere contralateral to the contractions. When the stories were compared to ones told in a control, no contraction condition, it was found that the differences between the left and right contractions were attributable to the effects of either one or the other depending on the control condition responses to the pictures. The results therefore provide evidence for both left and right hemisphere involvement in emotion.

The Consequences of Experimentally Induced and Chronic Unilateral Pain: Reflections of Hemispheric Lateralization of Emotion

In a series of three studies with right handed subjects, left side pain is tolerated less well than right side pain with a cold pressor, and results in greater emotional disturbance, both with a cold pressor and in chronic pain patients. In the second study where comparisons are made with non-stimulated controls, acute left side pain results in higher state anxiety scores than controls; right side pain and control groups are comparable. The differences between the reactions to left and right side pain are consistent with activation of the emotional properties of the hemisphere contralateral to the painful stimulation.

Effect of unilateral contraction of hand muscles on perceiver biases in the perception of chimeric and neutral faces

Judgements of chimeric faces (half sad, half happy) showed a strong negative bias when the left face was negative. Contractions of the right hand reduced this bias but left hand contractions had no effect. The left positive faces elicited weak positive response biases that were not strongly affected by either contraction. Faces that were drawn to be neutral elicited negative or positive response biases depending on the method of presentation. When this bias was negative under control conditions left contraction had no effect, but the bias became positive following right contractions. Similarly, when the control bias was positive the right contraction had no effect, but the bias became negative following left contractions. The results are interpreted as reflecting emotional changes and shifts in lateral attention resulting from activation of the hemisphere contralateral to the contraction.

Facial asymmetries in the spontaneous response to positive and negative emotional arousal

Facial asymmetries during emotional arousal were studied under conditions designed to produce spontaneous responses. Subjects who performed a difficult verbal task reported unpleasant emotions, tested high on state anxiety and showed greater changes in left than right-sided composite photographs compared to the relaxed state. Subjects who performed an easy version of the same task reported positive emotions, tested significantly lower on state anxiety and showed greater changes in right sided composites. The pattern of results is consistent with the lateralization of function for positive and negative emotions and not for cognitive task variables, however, a cognitive basis for these results cannot be categorically excluded. The role of arousal in the appearance of facial asymmetries is discussed.

Unilateral Facial Contractions Produce Mood Effects on Social Cognitive Judgements

This study demonstrates that left and right unilateral facial contractions have similar effects on the expression of ethnic stereotypes as do negative and positive moods induced by more conventional means. Subjects who con tracted the left side of their face (negative mood inducer) were more likely to express negative stereotypes of ethnic groups than were subjects who contracted the right side of their face (positive mood inducer). This parallels previous findings obtained using two standard mood inductions: the Veltens mood induction procedure; and a musical mood induction procedure. Given that unilateral facial contractions manipulate mood without cognitive involvement, this mood induction may have advantages over previously used procedures, the effects of which are subject to cognitive mediation explanations. In addition, these results suggest that, at least for the expression of ethnic stereotypes, moods influence on cognition does not depend on a cognitive component of mood induction.

Unilateral vibrotactile stimulation induces emotional biases in cognition and performance.

We administered 24 min of unilateral vibrotactile stimulation to the left or right ventral forearm of experimental participants. A separate control group did not receive stimulation but completed all experimental tasks. Participants who received right-side stimulation persisted more in attempting to solve insoluble puzzles and also made more positive judgments about an emotionally neutral film compared to participants who received left-side stimulation. The performance of the control group was intermediate to that of the stimulation groups, but was significantly different only from the right stimulation group. The absence of a significant left-side stimulation effect is not readily interpretable because floor effects may have limited the attenuating effects of left-side stimulation on persistence in problem solving. Emotional biases in cognition and performance resulting from unilateral vibrotactile stimulation can be explained with reference to activation of structures involved in the processing of emotion within the contralateral cerebral hemisphere, and by the laterality of emotion specified in the Valence Hypothesis. These results support the contention that similar biases elicited by unilateral muscle contractions result from their sensory consequences.

Long-term effects of caudate nucleus lesions on body weight in the rat

Abstract Lesions placed bilaterally in the caudate nucleus of albino rats produced only small transient depressions in body weight immediately after the operation. However over the following 240 days the lesioned animals grew more slowly and achieved lower and premature asymptotic weights compared to their matched controls. Logical and empirical considerations mitigate against sensory or motor interruption of feeding as a basis of these changes. Rather striatal influences on mechanisms which regulate and control growth are indicated.

Response-dependent effects of morphine on reinforcing lateral hypothalamic self-stimulation.

The effects of morphine (10mg/kg) on intracranial self-stimulation were studied in three separate test situations, each requiring rats to perform different types of responses. Self-stimulation was depressed in a test of rate of bar-pressing, to a lesser extent in a test of rate of wall-pressing in which a wider range of movements were reinforced, but not in a shuttle-box, with brain stimulation continuously available on one side of box. This response dependency suggests that the depressive effect of morphine on bar-pressing for lateral hypothalamic stimulation reflects a performance deficit rather than an effect on the reinforcing value of the stimulation.

Unilateral Contraction of Facial Muscles Do Effect Emotions: A “Failed Replication's” Failure to Perform a Replication

Kop, Merckelbach and Muris (1991) reported a failure to replicate Schiff and Lamons (1989) finding that unilateral muscle contractions induce emotions and influence cognitions in a manner which reflect those emotions. However, the procedures they used were different from the original experiment in substantive ways. These differences are described and it is explained how they account for the failure to replicate. This discussion helps illustrate the nature of the phenomenon which has been shown to be both robust and clinically relevant.