Table 1.
Summary table of included studies.
| References | Study type | Participants | Intervention | Outcome measures | Findings |
|---|---|---|---|---|---|
| STUDIES IN PARTICIPANTS WITH ASPD | |||||
| Timmerman et al. (27) | Randomized, controlled, double blind, placebo crossover trial | 22 adults with ASPD (14 males 8 females) and 29 healthy controls (11 females, 18 males) | IN OT (24 IU) or placebo | Participants were shown images of faces showing various emotions and assessed on their ability to accurately identify the emotion displayed and the time delay for this | Relative deficits in the ASPD group recognizing fearful and happy faces were no longer observable under OT |
| Alcorn et al. (28) | Single blind placebo controlled trial | 6 male participants with ASPD | IN OT (12, 24, 48 IU) or placebo | Performance on a validated laboratory task of human aggression (point subtraction aggression paradigm—PSAP) | There were few differences between those on placebo and those with OT in performance on the PSAP |
| STUDIES IN HEALTHY PARTICIPANTS | |||||
| Studies in empathy | |||||
| Human et al. (29) | Randomized, controlled, double blind placebo controlled trial | 116 healthy participants | IN OT (40 IU) or placebo | Following being helped on a task participants affect and social perceptions were rated | In the context of being helped by a stranger oxytocin fostered more positive affective and social responses |
| Hubble et al. (30) | Randomized, controlled, double blind, placebo within subject trial | 40 healthy males | IN OT (24 IU) or placebo | Participants completed questionnaires which provided empathy scores after being shown emotion eliciting video clips. In addition the eye tracking of the participants was assessed | OT was associated with an increase in time spent fixating upon the eye region of the protagonists face across emotions. OT selectively enhanced self-reported affective empathy for fear but not other emotions. There was no positive relationship between eye gaze patterns and affective empathy |
| Hecht et al. (31) | Randomized, double blind, placebo controlled trial | 28 healthy females | IN OT (24 IU) or placebo | Neural responses on fMRI to participants being shown animations of geometric shapes depicting social interactions | Lower social processing at baseline at baseline predicts a more positive response to OT |
| Li et al. (32) | Randomized, controlled, double blind, placebo within subject trial | 30 healthy fathers of 1-2 year old children | IN OT (24 IU) or IN AVP (20 IU) followed by placebo | Brain function was measured with fMRI with the participants viewing images of their children, unknown children and unknown adults as they listened to a crying stimulus | OT but not AVP increased the participants responses to images of their own children |
| Luo et al. (33) | Randomized, controlled, double blind placebo controlled trial. | 86 healthy participants | IN OT (24 IU) or placebo | Brain function was measured with fMRI with the participants viewing a range of images of emotional faces | Oxytocin produces sex dependent effects even at the early stages of social processing |
| Strang et al. (34) | Randomized, controlled, double blind placebo controlled trial | 132 healthy male participants | IN OT (24 IU) or placebo | Performance on a social discounting task as a measure of generosity | The effect of oxytocin on generous behavior is modulated by trait empathy. In those who were administered oxytocin there was a positive correlation between trait empathy and their generosity |
| Hi et al. (35) | Randomized double bind cross over study | 41 healthy males | IN OT (24 IU) or placebo | Performance on the “HelPun” task to examine the altruistic decision making of participants to help or punish others in the task. fMRI scanning before and after OT or placebo administration | In the OT group there was a trend to accelerate altruistic decision making. In the OT group there was enhanced activity in the left temporo parietal junction during observation of others being helped by the computer. These results indicated that OT enhances prosocial revelant perception by increasing theory of mind related neural activities |
| Korb et al. (36) | Randomized, double blind, placebo controlled, between subject trial | 60 healthy male participants | IN OT 24 IU or placebo | Performance on the Offset and Intensity facial mimicry tests as assessed compared with baseline facial EMG | Facial mimicry was increased in the OT group. These effects were strongest for angry infant faces |
| Palgi et al. (37) | Double blind, within subject placebo randomized controlled trial | 30 male and female participants | Single dose IN OT (24 IU) or placebo | Participants listened to recording of mixed gender protagonists describing distressing emotional conflicts and were then asked to provide compassionate advice | In male and female participants OT enhanced compassion toward females but not males |
| Perry et al. (38) | Randomized double blind placebo controlled trial | 54 male participants | Single dose IN OT (24 IU) or placebo | Online questionnaire assessing empathy Experiment involved participants indicating their preferred interpersonal distance | Among highly empathetic individuals OT promoted choice of closer interpersonal distances while the opposite effect was found in individuals with low empathetic traits |
| Gallup and Church (39) | Randomized double blind placebo control trial | 60 male healthy participants | Single dose IN OT (30 IU) or placebo | Exposure to a continuous yawning video | OT did not increase contagious yawning but modulated expression indicative of awareness of social stigma associated with this behavior |
| Abu-Akel et al. (40) | Double blind placebo controlled crossover trial | 29 male and female participants | Single dose IN OT (24 IU) or placebo | Self-perspective empathy vs. other perspective empathy in painful and non-painful situations | OT but not placebo, increased other perspective empathy |
| Cardoso et al. (41) | Randomized double blind placebo control trial | 82 male and female participants | Single dose IN OT (24IU) or placebo | Perceiving and understanding emotion components of MSCEIT.= | OT led to participants rating emotion in facial stimuli as expressing greater emotional intensity than those on placebo. Accurate identification of type of emotion in faces impaired in OT group.= |
| Fischer-Shofty et al. (42) | Double blind placebo controlled crossover trial | 62 male and female participants | Single dose IN OT (24 IU) or placebo | Interpersonal perception task | OT improved accurate perception of social interactions. OT also had sex specific impacts—improved kinship recognition within women but not men; performance of males was only improved on competition recognition |
| Studies in inhibitory control | |||||
| Hirosawa et al. (43) | Single blind placebo controlled crossover study | 20 male participants | IN OT (24 IU) or placebo | Paradigm 1: Facial cognition. Paradigm 2: attentional-inhibitory control using a modification of the speeded flanker task. | No significant behavioral effects of OT. However, the enhancement of attentional inhibitory control after OT administration significantly correlated to the positively valenced effects of the interpretation of uncertain facial cognition |
| Ma et al. (44) | Double blind placebo controlled between subject design | 150 Male participants | IN OT (24 IU) or placebo | Task of in-group favoritism where cognitive processing was experimentally manipulated. Participants were also assessed for intuition or reflection in daily life | OT increased in-group favoritism in intuitive participants but decreased it in those who rely on reflective style |
| Studies in compliance and conformity | |||||
| Aydogan et al. (45) | Randomized, double blind, placebo controlled trial | 120 healthy males | IN OT (24 IU) or placebo | Performance on a competitive and noncompetitive coin tossing task, where participants would self-report in order to win a monetary prize. This task was to measure conformity to the widely accepted norm of honesty under the pressure of competition in the OT group compared with the placebo group | Conformity was enhanced by oxytocin and this enhancement had a detrimental effect on honesty in a competitive environment but not in a noncompetitive environment |
| Gross and De Dreu (46) | Randomized, controlled, double blind, placebo within subject trial | 139 healthy participants | IN OT (24 IU) or placebo | Performance on a test of conformity to instructions. In the test, participants had a binary choice and were given an arbitrary rule that would mean that they would receive a lesser financial benefit | Under oxytocin participants violated the rule more often. This was most apparent in individuals who had a high need for structure |
| Lambert et al. (47) | Randomized, double blind, placebo controlled trial | 30 healthy females | IN OT (24 IU) or placebo | Participants performance on 2 social dilemma games was measured whilst participants were also shown social cues in the form of pictures of neutral or angry faces. During the tasks, an fMRI scan was conducted | OT significantly increased the activation of the nucleus accumbens during an assurance game that rewards mutual cooperation. OT significantly attenuates the amygdala |
| Ten Velden et al. (48) | Randomized, controlled, double blind, placebo within subject trial | 65 healthy males and 129 healthy female participants | IN OT (24 IU) or placebo | Participants were placed in groups and given tasks to test the levels of cooperation with the in-group. The task involved the group deciding to make an within group contribution or a between group contribution, Prior to the decision to contribute participants undertook a Stroop Interference task that was either cognitively taxing or not | Participants receiving placebo contributed more to the within group when they were cognitively taxed. The OT group contributed to the within group regardless of cognitive taxation |
| Hertz et al. (49) | Randomized, double blind, placebo controlled trial | 90 healthy male participants | IN OT (40 IU) or placebo | Performance in paired dyads on a visual search task | Compared to the placebo group there was a greater collective benefit over time in the OT group. In the OT group, the more competent member of each dyad was less likely to change his mind during disagreements |
| Edelson et al. (50) | Within subject randomized control cross over design | 92 male healthy participants | Single dose IN OT (24 IU) or placebo | Overt compliance Lasting changes to memory | OT enhanced compliance with erroneous opinions of others, and decreased influence of others on long term memories |
| Huang et al. (51) | Randomized double blind placebo controlled trial | 85 male participants | Single dose IN OT (24 IU) or placebo | Facial attractiveness judgment scale rating unfamiliar Chinese female faces; subsequently participants were informed of ratings given by peers from an in-group (Chinese) and out-group (Japanese) simultaneously and then were asked to re-rate the same faces | OT increased conformity to both in and out group opinions. |
| Lane et al. (52) | Two double blind randomized control trials | 1st trial-−95 male participants 2nd trial-−61 male participants | Single dose IN OT (32 IU) or placebo | Both trials employed an envelope task exploring trust, compassion and openness | There was no significant effect of in either of the trials |
| Ruissen et al. (53) | Randomized double blind between subject controlled trial | 63 healthy male participants | Single dose IN OT (24 IU) or placebo | Performance individually and on joint completion of the Simon task and EEG recordings during individual and joint performance on the Simon task | There was an enhanced Simon effect in the social context after administration of OT. Oxytocin enhanced self other integration compared with placebo on the N2 component of the EEG |
| Declereck et al. (54) | Double blind control trial | 259 male and female participants | 3 doses, at 5 minute intervals of IN OT (24 IU) or placebo | Participants played a range of mixed emotive games (prisoners dilemma); one group was subject to a social cue prior to completion | OT and social cues interact to alter the behaviors of individuals with a pro self-value orientation; after prior contact with the game partner, OT enhances cooperative behavior compared to anonymous conditions where it exacerbates intrinsic self-interest behavior |
| Shalvi and De Drue (55) | Double blind placebo controlled trial | 60 male participants | Single dose IN OT (24 IU) or placebo | Coin toss prediction task; participants were able to report their performance levels dishonestly to benefit their group | Healthy males in OT group lied more to benefit their group and did so faster than placebo group. Treatment effects emerged when lying had financial consequence |
| Yao et al. (56) | Double blind between subject placebo controlled trial | 104 male and female participants | Single dose IN OT (24 IU) or placebo | Revised version of a trust game with 5 players (1 truster, 4 trustees). The participant was always the truster and the trustees were not real | Although OT had no effect on modulating trust restoration, it did have a gender specific effect, with females showing less evidence for trust repair in OT vs. placebo groups |
| Israel et al. (57) | Randomized placebo control trial | 84 male participants | Single dose IN OT (24 IU) or placebo | Clips using an adaptation of the prisoner's dilemma task. Participants' financial awards were contingent on their own and their partner's decisions | OT participants were less accurate than those on placebo at predicting participants' decisions |
| Rilling et al. (58) | Randomized double blind placebo control trial. | 91 male participants | IN OT (24 IU) or Placebo or IN vasopression (140 IU) | Iterative prisoners dilemma game looking at behavioral and fMRI responses. | fMRI results showed that OT, relative to both vasopressin, and placebo increased caudate nucleus response to reciprocated cooperation and left amygdala activation to reciprocated cooperation. Behaviorally OT was associated with increased rates of cooperation |
| Studies in aggression and violence | |||||
| Ne'eman et al. (59) | Randomized, double blind, placebo controlled within subject trial | 48 healthy adults participants (28 men and 20 women) | IN OT (24 IU) or placebo | Performance on a Social Orientation Paradigm (SOP) to measure for real time aggressive behavior in response to provocation | In those naive to the SOP, oxytocin increased the aggressive response in comparison with placebo |
| DeWall et al. (60) | Double blind placebo controlled between subject experiment | 93 male and female participants | Single dose IN OT (24 IU) or placebo | Participants took part in 2 provocation tasks with participants rating the probability that they would engage in various aggressive behaviors with an intimate partner | OT increased interpersonal violence inclinations but this effect was limited to participants prone to physical aggression |
| Studies in moral responsibility | |||||
| Goodyear et al. (61) | Randomized double blind placebo controlled, between subject design | 84 male healthy participants | Single dose IN OT (40 IU) or placebo | Intuitions about free will and moral responsibility using ratings of vignettes in deterministic and indeterministic universes | Placebo group held offender more morally responsible compared to OT group |
| Scheele et al. (62) | Counter balanced, within subject double blind trial | 157 male and female participants | Single dose IN OT (24 IU) or placebo | Rating of intensity of own emotional arousal to pictures of faces during fMRI scanning. | OT facilitated cortical midline responses during the self processing of disgust and selectively promoted self interest moral judgments in men. In women OT increased the reaction time difference between accepted and rejected moral dilemmas. |