This thesis provides empirical evidence on the relation between concentrated ownership and the long term operating performance of acquiring firms. Large shareholders are generally viewed as beneficial monitors of corporate performance but high levels of concentration can lead to potential expropriation from minority shareholders via managerial entrenchment, tunneling, or sub-optimal investment decisions. This problem is potentially greater in firms with separation of voting and ownership rights. This thesis investigates the performance around takeovers in English origin countries other than the US by following the classification of La Porta, Lopez-de-Silanes, Shleifer and Vishny (1998). While generally considered similar to the US, these countries vary with respect to ownership concentration and investor protection. This thesis controls a broad set of corporate governance mechanisms including first generation governance measures like CEO positions, board characteristics, and other blockholders. Furthermore, this thesis also examines whether different degrees of second generation governance mechanisms such as anti-director rights, accounting standards, legal enforcement, and extra-legal institutions lead to different levels of M&A performance. In addition, this thesis includes the new legal indexes recently developed by Djankov, La Porta, Lopez-de-Silanes and Shleifer (2006); these measures have yet to be examined through empirical research. By using an accounting based methodology, this thesis presents Healy, Palepu and Ruback (1992) abnormal post cash flow return regression-based results and results of a change model (Ghosh 2001). Moreover, this thesis refers to the sample matching techniques in Barber and Lyon (1996) and develops the industry, size, and pre performance benchmark. The principal finding of this thesis is that M&A transactions should improve the long-term financial and operating performance of merging firms to reflect that accounting performance can capture real economic creations. After controlling for well documented governance mechanisms and deal characteristics, the relationship between concentrated ownership and the level and change in operating cash flow returns after takeovers is non-linear. Value creating deals are associated with higher levels of concentration consistent with decreasing agency costs as the large shareholder’s wealth invested in the acquiring firm increases. Further, separation of ownership and voting rights leads to greater value destruction; acquiring firms with controlling CEO make significant improvements in post acquisition performance after controlling pre-performance; and the presence of CEO-Chairman duality and board size are both significantly negatively associated with acquisition operating performance. This thesis also finds, although all acquiring firms are from English origin countries, that the greater investor protection, as measured by the initial anti-director right index in La Porta et al. (1998) and revised anti-director rights index in Djankov et al. (2006) has a positive impact on operating cash flow returns from acquisitions. However, this thesis does not document any differential performance with respect to the extra- legal systems of Dyck and Zingales (2004) and the anti-self-dealing index of Djankov et al. (2006).

本研究利用兩種時間關聯之操作式制約行為作業探討韁核的行為功能，一為區辨性增強低頻反應作業（簡稱DRL作業），另一為固定時距作業（簡稱FI作業）。本研究以神經毒素鵝膏蕈酸（ibotenic acid）破壞韁核的方式來測試大白鼠受試在上述行為作業之不同歷程的影響效果，包含習得歷程、行為表現階段以及已習得後轉換得酬賞之反應標準等三個階段。實驗一的結果顯示破壞韁核對於DRL作業的習得歷程具有明顯的影響，其影響效果在DRL短時距作業中造成無法以有效率的壓桿反應模式獲得酬賞；反之，破壞操弄的效果並不影響FI長與短時距作業的習得歷程。實驗二的結果顯示破壞韁核並不影響已習得的DRL作業與FI作業的行為表現，兩項作業的實驗組受試皆能維持穩定的行為反應模式且與控制組無明顯差異。實驗三對已習得的DRL行為進行時距參數的轉換（含調高及降低兩部份），結果顯示破壞韁核之操弄並未明顯的影響這項轉換新的時距之作業要求，但實驗組受試的確比控制組較遲緩達到新的時距要求。綜合而言，本研究以專屬性較高的神經毒素破壞韁核，用較多元指標的行為分析方式探討韁核的行為功能；其結果發現韁核參與DRL行為內含的區辨學習與對於錯誤偵測的負向迴饋，這些功能是需要透過韁核與其他中腦及邊緣系統的組織互動。 / This study examined the function of habenula (Hb) by two kinds of operant conditioned behavior tasks based on temporal contingency, including the differential reinforcement of low-rate responding (DRL) task and fixed-interval (FI) task. The effects of Hb lesion induced by neurotoxin ibotenic acid were examined at the different stages of operant conditioned behavior, including acquisition, performance, and transition stages. The results showed that bilateral lesions of Hb did not affect the locomotor activity and the basic lever-pressing. In Experiment 1, Hb lesion group had less reinforced responses and lower peak time indicating the deficits of acquisition of the DRL task. In contrast, the same lesion manipulation on the FI task did not produce any difference between the lesion group and the control group. The data of Experiment 2 showed that Hb lesion did not significantly affect the learned behavior maintained on DRL-10s or FI-30s schedule. In Experiment 3, Hb lesion produced a subtle, but not significant, impairment on behavioral transition from a learned interval to a newly-set interval (upward or downward). The lesioned subjects made a slower transition than the controls. In conclusion, these data suggest that the function of habenula is involved in discrimination learning and error detection for acquiring DRL behavior. However, it is likely that these Hb functions have to rely upon dynamic relationship between Hb and other midbrain limbic systems.