Perry et al. (Personal Space)

This study sits where the social and biological meet, so understanding three ideas makes it click.

1. Personal space (interpersonal distance). We each keep a comfortable 'bubble' of space around us; when others come too close we feel uncomfortable. The size of this bubble depends on the relationship (we let friends closer than strangers) and the situation — a clear example of the social approach's idea that the presence of others shapes behaviour.

2. Oxytocin — the 'social hormone'. Oxytocin (OT) is a hormone linked to social bonding, trust and affiliation (e.g. between parent and child, or partners). Researchers wondered whether giving extra oxytocin (as a nasal spray) would make people want to be closer to others. Earlier findings were mixed — which is the puzzle this study addresses.

3. Empathy and individual differences. Empathy is the ability to understand and share another person's feelings. People differ in how empathic they are. Perry et al. measured it using the Interpersonal Reactivity Index (IRI), a self-report questionnaire, and split participants into high and low empathy groups. Their key hypothesis was that oxytocin's effect on personal space would depend on how empathic a person already is.

Why a double-blind, placebo design? Because expectations could change behaviour, participants received either oxytocin or an identical placebo spray, and neither the participant nor the researcher interacting with them knew which (double-blind). This controls demand characteristics and experimenter effects, isolating the hormone's true effect.

Psychology being investigated: interpersonal distance (personal space), social hormones (oxytocin) and empathy.

Aim. To investigate whether oxytocin affects people's preferred interpersonal distance (personal space), and crucially whether this effect is modulated by empathy — i.e. whether oxytocin makes highly empathic people prefer to be closer to others, while affecting less empathic people differently. A placebo condition allowed comparison with no drug.

Sample: healthy adult male volunteers (around 20 per experiment). Only males were used to avoid hormonal-cycle confounds in women. Participants completed the Interpersonal Reactivity Index (IRI) and were classified as high or low empathy.

Design: a double-blind, placebo-controlled experiment with a repeated-measures (crossover) design — each participant received intranasal oxytocin on one session and placebo on another, about a week apart (order counterbalanced). Neither participant nor tester knew which spray was which.

Experiment 1 — the Comfortable Interpersonal Distance (CID) task (computerised).

• A figure on screen 'approached' the participant from different directions; the participant pressed a key to stop it at the distance that felt comfortable.
• Different approachers were used, e.g. a stranger, a friend, an authority figure, and a ball (a non-social control).

Experiment 2 — choosing pictures of rooms.

• Participants chose between pictures showing two people at different distances in a room, indicating their preferred interpersonal distance — a different way of measuring the same idea (helping to confirm Experiment 1).

Results:

• Oxytocin did not have a single, uniform effect. Its effect depended on empathy:
  • For high-empathy individuals, oxytocin led them to prefer/allow a closer interpersonal distance (a smaller CID).
  • For low-empathy individuals, oxytocin led them to prefer a larger distance (the opposite direction).
• Experiment 2 (room choice) supported the pattern found in Experiment 1.
• The effects were specific to social stimuli, not the non-social ball control.

Conclusion:

• Oxytocin's effect on social behaviour (here, personal space) is modulated by individual empathy — it promotes closeness only in highly empathic people.
• Personal space is influenced by both a social hormone and individual differences, supporting the social approach (the presence of others) interacting with biology.
• This helps explain why earlier oxytocin studies gave mixed results — they ignored the role of empathy.

Strengths

• High control + double-blind, placebo design — controls demand characteristics and experimenter effects, so the hormone's effect can be isolated. Very scientific and replicable.
• Repeated measures — each participant acts as their own control, removing participant variables.
• Two experiments (replication) with objective computerised measurement (CID), plus a non-social ball control to show the effect is social-specific.

Weaknesses

• All-male sample — to avoid hormonal-cycle confounds, only men were tested, so the findings may not generalise to women.
• Small sample (around 20 per experiment) → limited generalisability.
• Low ecological validity — judging distance to a figure on a computer screen (or in a picture) is not the same as real-life closeness to a real person.
• Ethics of giving a hormone — administering oxytocin has possible side effects (though risks were minimised).

Issues & debates

• Individual & situational explanations: personal space is shaped by the situation/other person AND by the individual trait of empathy — and by biology (oxytocin). A clear interaction.
• Application to everyday life: understanding social difficulties (e.g. autism, social anxiety) and the careful, individual-specific use of oxytocin in therapy.