Université de Fribourg

Endogeneity and non-response bias in treatment evaluation - nonparametric identification of causal effects by instruments

Fricke, Hans ; Frölich, Markus ; Huber, Martin ; Lechner, Michael

(Working Papers SES ; 459)

This paper proposes a nonparametric method for evaluating treatment effects in the presence of both treatment endogeneity and attrition/non-response bias, using two instrumental variables. Making use of a discrete instrument for the treatment and a continuous instrument for nonresponse/attrition, we identify the average treatment effect on compliers as well as the total population and suggest...

Université de Neuchâtel

Interspecific Communicative and Coordinated Hunting between Groupers and Giant Moray Eels in the Red Sea

Bshary, Redouan ; Hohner, Andrea ; Ait-el-Djoudi, Karim ; Fricke, Hans

In: Plos Biology, 2006, vol. 4, no. 12, p. 2393-2398

Intraspecific group hunting has received considerable attention because of the close links between cooperative behaviour and its cognitive demands. Accordingly, comparisons between species have focused on behaviours that can potentially distinguish between the different levels of cognitive complexity involved, such as “intentional” communication between partners in order to initiate a joint...

Université de Neuchâtel

Fish cognition : a primate's eye view

Bshary, Redouan ; Wickler, Wolfgang ; Fricke, Hans

In: Animal Cognition, 2002, vol. 5, p. 1-13

We provide selected examples from the fish literature of phenomena found in fish that are currently being examined in discussions of cognitive abilities and evolution of neocortex size in primates. In the context of social intelligence, we looked at living in individualised groups and corresponding social strategies, social learning and tradition, and co-operative hunting. Regarding environmental...