The excuse principle can maintain cooperation through forgivable defection in the Prisoner's Dilemma game

You mob my owl, I’ll mob yours: birds play tit-for-tat game

(2012) Tatjana Krama et al.   Scientific Reports

Resolving the iterated prisoner’s dilemma: theory and reality

(2011) N. J. RAIHANI et al.   JOURNAL OF EVOLUTIONARY BIOLOGY

Contingent cooperation between wild female baboons

(2010) D. L. Cheney et al.   PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA

Strategic Variation in Mobbing as a Front Line of Defense against Brood Parasitism

(2009) Justin A. Welbergen et al.   CURRENT BIOLOGY

Cooperation between non-kin in animal societies

(2009) Tim Clutton-Brock   NATURE

Mobbing calls signal predator category in a kin group-living bird species

(2009) M. Griesser   PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES

The increased risk of predation enhances cooperation

(2009) I. Krams et al.   PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES

Social Transmission of a Host Defense Against Cuckoo Parasitism

(2009) N. B. Davies et al.   SCIENCE

Group effect in nest defence behaviour of breeding pied flycatchers, Ficedula hypoleuca

(2008) Indrikis Krams et al.   ANIMAL BEHAVIOUR

Direct reciprocity with costly punishment: Generous tit-for-tat prevails

(2008) David G. Rand et al.   JOURNAL OF THEORETICAL BIOLOGY

Generosity: A winner's advice

(2008) Martin A. Nowak   NATURE