ResultsAttentional FocusPresence of others restricted the attentionalfocus: Participants showeda smaller flanker compatibility effect for the error rate when the experimenter was present:Significant interactionof flanker compatibilitywith condition for theerror rate, F(1,34) = 4.75,p = .04, but not for the reaction times, F(1,34) = 1.13, p = .3.

Social Presence Enhances Selective Spatial Attention Without Reducing Adaptation to Distractor UtilityJuliane Albert1, Henrik Singmann1, Julia Merkt1, Laura Schweikert1, Andreas Kappes1, Denis Köhler2, Caterina Gawrilow1, & Mike Wendt1

1 University of Hamburg 2 University of Applied Sciences Heidelberg

Summary• We found an effect of social presence on the general flanker

compatibility effect. This results adds evidence to the attentional account of social facilitation.

• We found no evidence for social presence effects on strategic adaption to flanker utility, hence no evidence for the notion of heightened arousal.

• However the experiments lacks (a) power and (b) a more direct test of the Zajonc hypotheses. Furthermore (c) the presence of the experimenter instead of a confederate plus the aversive sound leaves space for alternative explanations.

Introduction• The presence of others can facilitate or impede performance

in cognitive tasks: Social facilitation.Theoretical Introduction

Two theories provide different explanations for the phenomenon:

• The theory provided by Zajonc (1965) explains social facilitation effects with classical drive reduction theory:The presence of others leads to increased arousal. This should lead to an advantage for simple tasks (i.e., a increased tendency for dominant response) and a disadvantage for complex tasks (i.e., a decreased tendency for the non-dominant response).

• Baron (1986) suggests an explanation of attentional focusing: The presence of others leads to increased cognitive load. This narrows the attentional focus on task-relevant stimuli characteristics.

Empirical Evidence• Huguet et al. (1999) supported the attentional view with a

reduced Stroop compatibility effect when a confederate was present compared to task execution in isolation.

• However, the effect of narrowed attentional focus on Stroop compatibility effects is controversial. Chen (2003) found an increased Stroop compatibility effect with narrowed focus.

The present study We extended these findings in two ways.• First, to examine whether interference reduction also occurs

when target and distractor stimuli are presented at different locations, we used an Eriksen flanker task.

• Second, we manipulated the utility of flanker stimuli by varying the frequency of compatible (i.e. target and flanker stimuli are associated with the same response) and incompatible (i.e. target and flanker stimuli are associated with different responses) trials to investigate whether strategic adaptation (Botvinick et al., 2001) of the attentional focus is influenced by social presence.

• To investigate the effects on strategic adaption we also compared the flanker compatibility effect following compatible and incompatible trials (e.g., Gratton et al. 1992).

MethodsQuasi-experimental design: Control conditions of two experiments sharing the same paradigm, only differing in presence of experimenter.

Participants38 students: 18 alone, 20 with presence of experimenter.2 Outlier were excluded from the presence conditions:1 participant with extreme high error rate, z > 3, p < .003,1 participant with extreme high reaction time, z > 4, p < .001.

ProcedureIn condition of social presence the experimenter sat sideways to the participant. The experimenter was not able to observe the monitor.

Flanker taskStimuli: Digits from 2 to 9, flankers were single digits (e.g., 686), target and flanker always differed.Task: Participants had to judge the parity of the central digitQuantity: 8 blocks à 100 Trials: 4 blocks with mostly incompatible trials (80% incompatible), 4 blocks with mostly compatible trials (20% incompatible)On errors: aversive sound & signal on the screen

Example Trial

+ 838

400 ms 160 ms600 mst

ITI100 ms

Effect size (d) of flanker compatibility effect between conditions

p = .3

p = .04

ReferencesBaron, R. S. (1986). Distraction-conflict theory: Progress and problems. In: L. Berkowitz (Ed.), Advances

in experimental social psychology (pp. 1-40). New York: Academic Press.Botvinivck, M. M. , Braver, T. S., Barch, D. M., Carter, C. S., & Cohen, J. D. (2001). Conflict Monitoring

and Cognitive Control. Psychological Review, 108(3), 624- 652.Chen, Z. (2003). Attentional focus, processing load, and Stroop interference. Perception &

Psychophysics, 65(6), 888-900.Gratton, G., Coles, M. G., Donchin, E. (1992). Optimizing the use of information: Strategic control of

activation of responses. Journal of Experimental Psychology: General, 121(4), 480-506.Huguet, P., Galvaing, M.P., Montail, J. M., & Dumas, F. (1999). Social Presence Effects in the Stroop

Task: Further Evidence for an Attentional View of Social Facilitation. Journal of Personality and Social Psychology, 77(5), 1011-1025.

Zajonc, R. B. (1965). Social facilitation. Science, 149, 269-274.

Poster presented at the 21th Annual Convention of the Association for Psychological Science in San Francisco, CA, May 2009

Strategic Adaption• The flanker compatibility effect was reduced in blocks with high

percentage of incompatible trials compared to blocks with a low percentage of incompatible trials (E: p = .02, RT: p =.13).

• The flanker compatibility effect was smaller after incompatible trials than after compatible trials (E: p = .02, RT: p =.01).

• This strategic adaption of processing selectivity to the utility of flanker information did not differ whether the experimenter was present or not (ps > .3).